diff --git a/.github/workflows/compute-entropy.py b/.github/workflows/compute-entropy.py new file mode 100644 index 00000000000..42655913bb3 --- /dev/null +++ b/.github/workflows/compute-entropy.py @@ -0,0 +1,64 @@ +#!/usr/bin/env python3 +import sys, math, json, subprocess +from collections import Counter +from pathlib import Path + +def shannon_entropy(text: str) -> float: + if not text or len(text) < 10: + return 0.0 + freq = Counter(text) + probs = [count / len(text) for count in freq.values()] + return -sum(p * math.log2(p) for p in probs if p > 0) + +# Get changed files safely for pull_request events +changed_files = [] +try: + # GitHub provides github.event.pull_request.base.sha and head.sha in the context + base_sha = subprocess.check_output(['git', 'rev-parse', 'origin/${{ github.base_ref }}'], text=True).strip() + changed_files = subprocess.check_output( + ['git', 'diff', '--name-only', base_sha, 'HEAD'], text=True + ).splitlines() +except subprocess.CalledProcessError: + # Fallback for first-time PRs or edge cases: use the merge-base or just files in HEAD + try: + changed_files = subprocess.check_output( + ['git', 'diff', '--name-only', 'HEAD~1', 'HEAD'], text=True + ).splitlines() + except subprocess.CalledProcessError: + # Last resort: all files in the repo + changed_files = subprocess.check_output(['git', 'ls-files'], text=True).splitlines() + +results = [] +total_ent = 0.0 +count = 0 + +for f in changed_files: + path = Path(f.strip()) + if not path.exists() or path.suffix in {'.png', '.jpg', '.gif', '.bin', '.lock', '.exe', '.dll', '.so'}: + continue + try: + content = path.read_text(encoding='utf-8', errors='ignore') + ent = shannon_entropy(content) + results.append(f"{f}: {ent:.3f}") + total_ent += ent + count += 1 + except Exception: + pass + +avg = round(total_ent / count, 3) if count > 0 else 0.0 + +verdict = ( + "✅ Mid-4 beauty detected (thoughtful human code!)" if 4.3 <= avg <= 4.7 else + "⚠️ Consider review — entropy outside sweet spot" if avg > 0 else + "No source files changed" +) + +with open('/tmp/beauty.json', 'w') as f: + json.dump({ + "average_entropy": avg, + "verdict": verdict, + "files": results[:20] + }, f, indent=2) + +print(f"Average entropy: {avg}") +print(verdict) diff --git a/.github/workflows/entropy-beauty-scan.yml b/.github/workflows/entropy-beauty-scan.yml new file mode 100644 index 00000000000..0923ba510d0 --- /dev/null +++ b/.github/workflows/entropy-beauty-scan.yml @@ -0,0 +1,123 @@ +name: Entropy Beauty + TruffleHog Scan + +on: [push, release, pull_request, pull_request_target] + +permissions: + contents: read + pull-requests: write + issues: write # must be at workflow level for push/merge events + +jobs: + scan: + runs-on: ubuntu-latest + steps: + - name: Checkout code (full history) + uses: actions/checkout@v6 + with: + fetch-depth: 0 + + - name: Run TruffleHog + uses: trufflesecurity/trufflehog@main + with: + path: . + extra_args: --results=verified,unknown --filter-entropy=3.5 --json + + - name: Compute mid-4 beauty entropy + run: python .github/workflows/compute-entropy.py + + - name: Post summary comment (PR only) + if: github.event_name == 'pull_request' || github.event_name == 'pull_request_target' + uses: actions/github-script@v8 + with: + github-token: ${{ secrets.GITHUB_TOKEN }} + script: | + const fs = require('fs'); + + // Read TruffleHog output — it prints one JSON object per line (NDJSON) + let findings = []; + if (fs.existsSync('trufflehog.json')) { + try { + const lines = fs.readFileSync('trufflehog.json', 'utf8').trim().split('\n'); + findings = lines.map(line => { + try { return JSON.parse(line); } catch(e) { return null; } + }).filter(Boolean); + } catch(e) {} + } else { + // Fallback: the action also logs to GITHUB_STEP_SUMMARY, but we use the file from the Python step + console.log("No trufflehog.json found, using empty findings"); + } + + const beauty = JSON.parse(fs.readFileSync('/tmp/beauty.json', 'utf8')); + + let body = `## 🐷 TruffleHog + Entropy Beauty Scan\n\n`; + body += `**Average entropy of changed code:** ${beauty.average_entropy} bits/char\n`; + body += `**Verdict:** ${beauty.verdict}\n\n`; + + if (beauty.files && beauty.files.length) { + body += `**Changed files entropy:**\n\`\`\`\n${beauty.files.join('\n')}\n\`\`\`\n\n`; + } + + if (findings.length > 0) { + body += `⚠️ **TruffleHog found ${findings.length} potential issue(s)**\n`; + } else { + body += `✅ No secrets or suspicious high-entropy strings found.\n`; + } + + body += `\n*Mid-4 beauty heuristic in action — powered by our entropy chats! 😊*`; + + await github.rest.issues.createComment({ + owner: context.repo.owner, + repo: context.repo.repo, + issue_number: context.issue.number, + body: body + }); + # ── Create issue on push ONLY if suspicious (entropy outside 4.3–4.7) ── + - name: Create issue on suspicious push + if: github.event_name == 'push' || github.event_name == 'release' + uses: actions/github-script@v8 + with: + github-token: ${{ secrets.GITHUB_TOKEN }} + script: | + const fs = require('fs'); + const beauty = JSON.parse(fs.readFileSync('/tmp/beauty.json', 'utf8')); + + // Only create issue if it's NOT beautiful mid-4 + if (beauty.average_entropy >= 4.3 && beauty.average_entropy <= 4.7) { + console.log("✅ Mid-4 beauty — no issue created"); + return; + } + + let findings = []; + if (fs.existsSync('trufflehog.json')) { + try { + const lines = fs.readFileSync('trufflehog.json', 'utf8').trim().split('\n'); + findings = lines.map(line => { + try { return JSON.parse(line); } catch(e) { return null; } + }).filter(Boolean); + } catch(e) {} + } + + let body = `**Average entropy:** ${beauty.average_entropy} bits/char\n\n`; + body += `**Verdict:** ${beauty.verdict}\n\n`; + + if (beauty.files && beauty.files.length) { + body += `**Changed files:**\n\`\`\`\n${beauty.files.join('\n')}\n\`\`\`\n\n`; + } + + if (findings.length > 0) { + body += `**TruffleHog found ${findings.length} potential issue(s)**\n`; + } else { + body += `✅ No secrets or suspicious high-entropy strings found.\n`; + } + + body += `\n*Triggered by push to \`${context.sha}\` — mid-4 beauty heuristic*`; + + await github.rest.issues.create({ + owner: context.repo.owner, + repo: context.repo.repo, + title: `🚨 Suspicious entropy detected in recent push (${beauty.average_entropy})`, + body: body, + labels: ['entropy', 'security', 'review-needed'] + }); + + console.log("⚠️ Created issue because entropy was outside mid-4 range"); diff --git a/.github/workflows/gradle-wrapper-validation.yml b/.github/workflows/gradle-wrapper-validation.yml index 66ecaec87f8..4174da20727 100644 --- a/.github/workflows/gradle-wrapper-validation.yml +++ b/.github/workflows/gradle-wrapper-validation.yml @@ -1,10 +1,13 @@ name: "Validate Gradle Wrapper" on: [push, pull_request] +permissions: + contents: read + jobs: validation: name: "Validation" runs-on: ubuntu-latest steps: - - uses: actions/checkout@v2.4.0 - - uses: gradle/wrapper-validation-action@v1.0.4 + - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2 + - uses: gradle/wrapper-validation-action@f9c9c575b8b21b6485636a91ffecd10e558c62f6 # v3.5.0 diff --git a/.github/workflows/gradle_branch.yml b/.github/workflows/gradle_branch.yml index 500e984ff6f..ef7ad91cc20 100644 --- a/.github/workflows/gradle_branch.yml +++ b/.github/workflows/gradle_branch.yml @@ -7,19 +7,22 @@ on: push: branches-ignore: [ '3.x' ] +permissions: + contents: read + jobs: build: runs-on: ubuntu-latest steps: - - uses: actions/checkout@v2.4.0 - - name: Set up JDK 8 - uses: actions/setup-java@v2 + - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2 + - name: Set up JDK 11 + uses: actions/setup-java@be666c2fcd27ec809703dec50e508c2fdc7f6654 # v5.2.0 with: distribution: 'zulu' - java-version: '8' + java-version: '11' - name: Cache Gradle packages - uses: actions/cache@v2.1.7 + uses: actions/cache@cdf6c1fa76f9f475f3d7449005a359c84ca0f306 # v5.0.3 with: path: ~/.gradle/caches key: ${{ runner.os }}-gradle-${{ secrets.CACHE_VERSION }}-${{ hashFiles('**/*.gradle') }} @@ -29,6 +32,6 @@ jobs: - name: Build RxJava run: ./gradlew build --stacktrace - name: Upload to Codecov - uses: codecov/codecov-action@v2.1.0 + uses: codecov/codecov-action@671740ac38dd9b0130fbe1cec585b89eea48d3de # v5.5.2 - name: Generate Javadoc run: ./gradlew javadoc --stacktrace diff --git a/.github/workflows/gradle_jdk11.yml b/.github/workflows/gradle_jdk11.yml index 849edb55f8e..8eab1cf14a3 100644 --- a/.github/workflows/gradle_jdk11.yml +++ b/.github/workflows/gradle_jdk11.yml @@ -9,19 +9,25 @@ on: pull_request: branches: [ 3.x ] +permissions: + contents: read + +env: + BUILD_WITH_11: true + jobs: build: runs-on: ubuntu-latest steps: - - uses: actions/checkout@v2.4.0 + - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2 - name: Set up JDK 11 - uses: actions/setup-java@v2 + uses: actions/setup-java@be666c2fcd27ec809703dec50e508c2fdc7f6654 # v5.2.0 with: distribution: 'zulu' java-version: '11' - name: Cache Gradle packages - uses: actions/cache@v2.1.7 + uses: actions/cache@cdf6c1fa76f9f475f3d7449005a359c84ca0f306 # v5.0.3 with: path: ~/.gradle/caches key: ${{ runner.os }}-gradle-1-${{ hashFiles('**/*.gradle') }} @@ -32,5 +38,5 @@ jobs: run: ./gradlew -PjavaCompatibility=9 jar - name: Build RxJava run: ./gradlew build --stacktrace - - name: Generate Javadoc - run: ./gradlew javadoc --stacktrace +# - name: Generate Javadoc +# run: ./gradlew javadoc --stacktrace diff --git a/.github/workflows/gradle_pr.yml b/.github/workflows/gradle_pr.yml index d5f4f111945..815b14d9631 100644 --- a/.github/workflows/gradle_pr.yml +++ b/.github/workflows/gradle_pr.yml @@ -7,19 +7,22 @@ on: pull_request: branches: [ 3.x ] +permissions: + contents: read + jobs: build: runs-on: ubuntu-latest steps: - - uses: actions/checkout@v2.4.0 - - name: Set up JDK 8 - uses: actions/setup-java@v2 + - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2 + - name: Set up JDK 11 + uses: actions/setup-java@be666c2fcd27ec809703dec50e508c2fdc7f6654 # v5.2.0 with: distribution: 'zulu' - java-version: '8' + java-version: '11' - name: Cache Gradle packages - uses: actions/cache@v2.1.7 + uses: actions/cache@cdf6c1fa76f9f475f3d7449005a359c84ca0f306 # v5.0.3 with: path: ~/.gradle/caches key: ${{ runner.os }}-gradle-1-${{ hashFiles('**/*.gradle') }} @@ -29,6 +32,6 @@ jobs: - name: Build RxJava run: ./gradlew build --stacktrace - name: Upload to Codecov - uses: codecov/codecov-action@v2.1.0 + uses: codecov/codecov-action@671740ac38dd9b0130fbe1cec585b89eea48d3de # v5.5.2 - name: Generate Javadoc run: ./gradlew javadoc --stacktrace diff --git a/.github/workflows/gradle_release.yml b/.github/workflows/gradle_release.yml index c7ac3316d74..3d3ddc27f25 100644 --- a/.github/workflows/gradle_release.yml +++ b/.github/workflows/gradle_release.yml @@ -10,21 +10,26 @@ on: tags: - 'v3.*.*' +permissions: + contents: read + jobs: build: runs-on: ubuntu-latest + permissions: + contents: write env: CI_BUILD_NUMBER: ${{ github.run_number }} steps: - - uses: actions/checkout@v2.4.0 - - name: Set up JDK 8 - uses: actions/setup-java@v2 + - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2 + - name: Set up JDK 11 + uses: actions/setup-java@be666c2fcd27ec809703dec50e508c2fdc7f6654 # v5.2.0 with: distribution: 'zulu' - java-version: '8' + java-version: '11' - name: Cache Gradle packages - uses: actions/cache@v2.1.7 + uses: actions/cache@cdf6c1fa76f9f475f3d7449005a359c84ca0f306 # v5.0.3 with: path: ~/.gradle/caches key: ${{ runner.os }}-gradle-${{ secrets.CACHE_VERSION }}-${{ hashFiles('**/*.gradle') }} @@ -38,9 +43,18 @@ jobs: - name: Build RxJava run: ./gradlew build --stacktrace --no-daemon - name: Upload to Codecov - uses: codecov/codecov-action@v2.1.0 - - name: Upload release - run: ./gradlew -PreleaseMode=full publish --no-daemon --no-parallel --stacktrace + uses: codecov/codecov-action@671740ac38dd9b0130fbe1cec585b89eea48d3de # v5.5.2 +# - name: Upload release +# run: ./gradlew -PreleaseMode=full publish --no-daemon --no-parallel --stacktrace +# env: +# # Define secrets at https://github.com/ReactiveX/RxJava/settings/secrets/actions +# # ------------------------------------------------------------------------------ +# ORG_GRADLE_PROJECT_mavenCentralUsername: ${{ secrets.SONATYPE_USER }} +# ORG_GRADLE_PROJECT_mavenCentralPassword: ${{ secrets.SONATYPE_PASSWORD }} +# ORG_GRADLE_PROJECT_SIGNING_PRIVATE_KEY: ${{ secrets.SIGNING_PRIVATE_KEY }} +# ORG_GRADLE_PROJECT_SIGNING_PASSWORD: ${{ secrets.SIGNING_PASSWORD }} + - name: Publish release + run: ./gradlew -PreleaseMode=full publishAndReleaseToMavenCentral --no-configuration-cache --no-daemon --no-parallel --stacktrace env: # Define secrets at https://github.com/ReactiveX/RxJava/settings/secrets/actions # ------------------------------------------------------------------------------ @@ -48,13 +62,6 @@ jobs: ORG_GRADLE_PROJECT_mavenCentralPassword: ${{ secrets.SONATYPE_PASSWORD }} ORG_GRADLE_PROJECT_SIGNING_PRIVATE_KEY: ${{ secrets.SIGNING_PRIVATE_KEY }} ORG_GRADLE_PROJECT_SIGNING_PASSWORD: ${{ secrets.SIGNING_PASSWORD }} - - name: Publish release - run: ./gradlew -PreleaseMode=full closeAndReleaseRepository --no-daemon --no-parallel --stacktrace - env: - # Define secrets at https://github.com/ReactiveX/RxJava/settings/secrets/actions - # ------------------------------------------------------------------------------ - ORG_GRADLE_PROJECT_mavenCentralUsername: ${{ secrets.SONATYPE_USER }} - ORG_GRADLE_PROJECT_mavenCentralPassword: ${{ secrets.SONATYPE_PASSWORD }} - name: Push Javadoc run: ./push_javadoc.sh env: diff --git a/.github/workflows/gradle_snapshot.yml b/.github/workflows/gradle_snapshot.yml index fba3058d811..e56c9019aad 100644 --- a/.github/workflows/gradle_snapshot.yml +++ b/.github/workflows/gradle_snapshot.yml @@ -6,24 +6,29 @@ name: Snapshot on: push: branches: [ '3.x' ] + +permissions: + contents: read jobs: build: runs-on: ubuntu-latest if: github.repository == 'ReactiveX/RxJava' + permissions: + contents: write env: # ------------------------------------------------------------------------------ CI_BUILD_NUMBER: ${{ github.run_number }} steps: - - uses: actions/checkout@v2.4.0 - - name: Set up JDK 8 - uses: actions/setup-java@v2 + - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2 + - name: Set up JDK 11 + uses: actions/setup-java@be666c2fcd27ec809703dec50e508c2fdc7f6654 # v5.2.0 with: distribution: 'zulu' - java-version: '8' + java-version: '11' - name: Cache Gradle packages - uses: actions/cache@v2.1.7 + uses: actions/cache@cdf6c1fa76f9f475f3d7449005a359c84ca0f306 # v5.0.3 with: path: ~/.gradle/caches key: ${{ runner.os }}-gradle-${{ secrets.CACHE_VERSION }}-${{ hashFiles('**/*.gradle') }} @@ -35,14 +40,14 @@ jobs: - name: Build RxJava run: ./gradlew build --stacktrace --no-daemon - name: Upload Snapshot - run: ./gradlew -PreleaseMode=branch publish --no-daemon --no-parallel --stacktrace + run: ./gradlew -PreleaseMode=branch publishAllPublicationsToMavenCentralRepository --no-daemon --no-parallel --stacktrace env: # Define secrets at https://github.com/ReactiveX/RxJava/settings/secrets/actions # ------------------------------------------------------------------------------ ORG_GRADLE_PROJECT_mavenCentralUsername: ${{ secrets.SONATYPE_USER }} ORG_GRADLE_PROJECT_mavenCentralPassword: ${{ secrets.SONATYPE_PASSWORD }} - name: Upload to Codecov - uses: codecov/codecov-action@v2.1.0 + uses: codecov/codecov-action@671740ac38dd9b0130fbe1cec585b89eea48d3de # v5.5.2 - name: Push Javadoc run: ./push_javadoc.sh # Define secrets at https://github.com/ReactiveX/RxJava/settings/secrets/actions diff --git a/.github/workflows/scorecard.yml b/.github/workflows/scorecard.yml new file mode 100644 index 00000000000..26a487cffea --- /dev/null +++ b/.github/workflows/scorecard.yml @@ -0,0 +1,59 @@ +name: Scorecard supply-chain security +on: + # For Branch-Protection check. Only the default branch is supported. See + # https://github.com/ossf/scorecard/blob/main/docs/checks.md#branch-protection + branch_protection_rule: + # To guarantee Maintained check is occasionally updated. See + # https://github.com/ossf/scorecard/blob/main/docs/checks.md#maintained + schedule: + - cron: '43 12 * * 4' + push: + branches: [ "3.x" ] + +permissions: read-all + +jobs: + analysis: + name: Scorecard analysis + runs-on: ubuntu-latest + permissions: + # Needed to upload the results to code-scanning dashboard. + security-events: write + # Needed to publish results and get a badge (see publish_results below). + id-token: write + + steps: + - name: "Checkout code" + uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2 + with: + persist-credentials: false + + - name: "Run analysis" + uses: ossf/scorecard-action@4eaacf0543bb3f2c246792bd56e8cdeffafb205a # v2.4.3 + with: + results_file: results.sarif + results_format: sarif + # (Optional) "write" PAT token. Uncomment the `repo_token` line below if + # you want to enable the Branch-Protection check on a *public* repository + # To create the PAT, follow the steps in https://github.com/ossf/scorecard-action#authentication-with-fine-grained-pat-optional. + # repo_token: ${{ secrets.SCORECARD_TOKEN }} + + # - Publish results to OpenSSF REST API for easy access by consumers + # - Allows the repository to include the Scorecard badge. + # - See https://github.com/ossf/scorecard-action#publishing-results. + publish_results: true + + # Upload the results as artifacts (optional). Commenting out will disable uploads of run results in SARIF + # format to the repository Actions tab. + - name: "Upload artifact" + uses: actions/upload-artifact@bbbca2ddaa5d8feaa63e36b76fdaad77386f024f # v7.0.0 + with: + name: SARIF file + path: results.sarif + retention-days: 5 + + # Upload the results to GitHub's code scanning dashboard. + - name: "Upload to code-scanning" + uses: github/codeql-action/upload-sarif@0d579ffd059c29b07949a3cce3983f0780820c98 # v3.29.5 + with: + sarif_file: results.sarif diff --git a/.gitpod.yml b/.gitpod.yml new file mode 100644 index 00000000000..954870bba66 --- /dev/null +++ b/.gitpod.yml @@ -0,0 +1,139 @@ +## Learn more about this file at 'https://www.gitpod.io/docs/references/gitpod-yml' +## +## This '.gitpod.yml' file when placed at the root of a project instructs +## Gitpod how to prepare & build the project, start development environments +## and configure continuous prebuilds. Prebuilds when enabled builds a project +## like a CI server so you can start coding right away - no more waiting for +## dependencies to download and builds to finish when reviewing pull-requests +## or hacking on something new. +## +## With Gitpod you can develop software from any device (even iPads) via +## desktop or browser based versions of VS Code or any JetBrains IDE and +## customise it to your individual needs - from themes to extensions, you +## have full control. +## +## The easiest way to try out Gitpod is install the browser extenion: +## 'https://www.gitpod.io/docs/browser-extension' or by prefixing +## 'https://gitpod.io#' to the source control URL of any project. +## +## For example: 'https://gitpod.io#https://github.com/gitpod-io/gitpod' + + +## The 'image' section defines which Docker image Gitpod should use. +## By default, Gitpod uses a standard Docker Image called 'workspace-full' +## which can be found at 'https://github.com/gitpod-io/workspace-images' +## +## Workspaces started based on this default image come pre-installed with +## Docker, Go, Java, Node.js, C/C++, Python, Ruby, Rust, PHP as well as +## tools such as Homebrew, Tailscale, Nginx and several more. +## +## If this image does not include the tools needed for your project then +## a public Docker image or your own Docker file can be configured. +## +## Learn more about images at 'https://www.gitpod.io/docs/config-docker' + +#image: node:buster # use 'https://hub.docker.com/_/node' +# +#image: # leave image undefined if using a Dockerfile +# file: .gitpod.Dockerfile # relative path to the Dockerfile from the +# # root of the project + +## The 'tasks' section defines how Gitpod prepares and builds this project +## or how Gitpod can start development servers. With Gitpod, there are three +## types of tasks: +## +## - before: Use this for tasks that need to run before init and before command. +## - init: Use this to configure prebuilds of heavy-lifting tasks such as +## downloading dependencies or compiling source code. +## - command: Use this to start your database or application when the workspace starts. +## +## Learn more about these tasks at 'https://www.gitpod.io/docs/config-start-tasks' + +#tasks: +# - before: | +# # commands to execute... +# +# - init: | +# # sudo apt-get install python3 # can be used to install operating system +# # dependencies but these are not kept after the +# # prebuild completes thus Gitpod recommends moving +# # operating system dependency installation steps +# # to a custom Dockerfile to make prebuilds faster +# # and to keep your codebase DRY. +# # 'https://www.gitpod.io/docs/config-docker' +# +# # pip install -r requirements.txt # install codebase dependencies +# # cmake # precompile codebase +# +# - name: Web Server +# openMode: split-left +# env: +# WEBSERVER_PORT: 8080 +# command: | +# python3 -m http.server $WEBSERVER_PORT +# +# - name: Web Browser +# openMode: split-right +# env: +# WEBSERVER_PORT: 8080 +# command: | +# gp await-port $WEBSERVER_PORT +# lynx `gp url` + +tasks: + - command: ./gradlew build + +## The 'ports' section defines various ports your may listen on are +## configured in Gitpod on an authenticated URL. By default, all ports +## are in private visibility state. +## +## Learn more about ports at 'https://www.gitpod.io/docs/config-ports' + +#ports: +# - port: 8080 # alternatively configure entire ranges via '8080-8090' +# visibility: private # either 'public' or 'private' (default) +# onOpen: open-browser # either 'open-browser', 'open-preview' or 'ignore' + + +## The 'vscode' section defines a list of Visual Studio Code extensions from +## the OpenVSX.org registry to be installed upon workspace startup. OpenVSX +## is an open alternative to the proprietary Visual Studio Code Marketplace +## and extensions can be added by sending a pull-request with the extension +## identifier to https://github.com/open-vsx/publish-extensions +## +## The identifier of an extension is always ${publisher}.${name}. +## +## For example: 'vscodevim.vim' +## +## Learn more at 'https://www.gitpod.io/docs/ides-and-editors/vscode' + +#vscode: +# extensions: +# - vscodevim.vim +# - esbenp.prettier-vscode@9.5.0 +# - https://example.com/abc/releases/extension-0.26.0.vsix + + +## The 'github' section defines configuration of continuous prebuilds +## for GitHub repositories when the GitHub application +## 'https://github.com/apps/gitpod-io' is installed in GitHub and granted +## permissions to access the repository. +## +## Learn more at 'https://www.gitpod.io/docs/prebuilds' + +github: + prebuilds: + # enable for the default branch + master: true + # enable for all branches in this repo + branches: true + # enable for pull requests coming from this repo + pullRequests: true + # enable for pull requests coming from forks + pullRequestsFromForks: true + # add a check to pull requests + addCheck: true + # add a "Review in Gitpod" button as a comment to pull requests + addComment: false + # add a "Review in Gitpod" button to the pull request's description + addBadge: true diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md index 98ae7225f3b..c1f0974f79c 100644 --- a/CONTRIBUTING.md +++ b/CONTRIBUTING.md @@ -4,6 +4,22 @@ If you would like to contribute code you can do so through GitHub by forking the When submitting code, please make every effort to follow existing conventions and style in order to keep the code as readable as possible. +## AI contributions + +We are not against contributions from AI tools, LLM-based or future architectures. However, you as a human are responsible for its contributions and suggestions. + +This means, you have to make sure it doesn't hallucinate issues or elements of the contribution, doesn't try to hack rewards or hack established unit tests, doesn't go wild +and rearchitect established components. + +If you post a contribution that is broken, we will not argue with your LLM or prompt engineer for you. You are responsible for having the the LLM's output work within the confines +of this project. + +Please also be aware that this project is large both in current and historical sense with some rules not documented or enforced by unit tests. This is because such unwritten rules +were trivial or readily inferrable by humans in the past. The project predates LLMs several years and thus is not organized to be accessible by LLMs today. Nor should it be. + +Consequently, the amount of prompting and the context window size to include all possible information about it could become so much that it can become prohibitively expensive to have +an LLM come up with more than basic and trivial contributions. Needless to say, don't bankrupt yourself and don't just accept the LLM's output at face value. + ## License By contributing your code, you agree to license your contribution under the terms of the APLv2: https://github.com/ReactiveX/RxJava/blob/3.x/LICENSE diff --git a/COPYRIGHT b/COPYRIGHT new file mode 100644 index 00000000000..5d2c6e53f3c --- /dev/null +++ b/COPYRIGHT @@ -0,0 +1,13 @@ +Copyright (c) 2016-present, RxJava Contributors. + +Licensed under the Apache License, Version 2.0 (the "License"); +you may not use this file except in compliance with the License. +You may obtain a copy of the License at + +http://www.apache.org/licenses/LICENSE-2.0 + +Unless required by applicable law or agreed to in writing, software +distributed under the License is distributed on an "AS IS" BASIS, +WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +See the License for the specific language governing permissions and +limitations under the License. \ No newline at end of file diff --git a/README.md b/README.md index 7449fa7f8be..5276c0bd375 100644 --- a/README.md +++ b/README.md @@ -2,7 +2,9 @@ [![codecov.io](http://codecov.io/github/ReactiveX/RxJava/coverage.svg?branch=3.x)](https://codecov.io/gh/ReactiveX/RxJava/branch/3.x) -[![Maven Central](https://maven-badges.herokuapp.com/maven-central/io.reactivex.rxjava3/rxjava/badge.svg)](https://maven-badges.herokuapp.com/maven-central/io.reactivex.rxjava3/rxjava) +[![Maven Central](https://maven-badges.sml.io/sonatype-central/io.reactivex.rxjava3/rxjava/badge.svg)](https://maven-badges.sml.io/sonatype-central/io.reactivex.rxjava3/rxjava) +[![Contribute with Gitpod](https://img.shields.io/badge/Contribute%20with-Gitpod-908a85?logo=gitpod)](https://gitpod.io/#https://github.com/ReactiveX/RxJava) +[![OpenSSF Scorecard](https://api.securityscorecards.dev/projects/github.com/ReactiveX/RxJava/badge)](https://securityscorecards.dev/viewer/?uri=github.com/ReactiveX/RxJava) RxJava is a Java VM implementation of [Reactive Extensions](http://reactivex.io): a library for composing asynchronous and event-based programs by using observable sequences. @@ -10,16 +12,19 @@ It extends the [observer pattern](http://en.wikipedia.org/wiki/Observer_pattern) #### Version 3.x ([Javadoc](http://reactivex.io/RxJava/3.x/javadoc/)) -- single dependency: [Reactive-Streams](https://github.com/reactive-streams/reactive-streams-jvm) -- Java 8+ or Android API 21+ required -- Java 8 lambda-friendly API -- [Android](https://github.com/ReactiveX/RxAndroid) desugar friendly -- fixed API mistakes and many limits of RxJava 2 -- intended to be a replacement for RxJava 2 with relatively few binary incompatible changes -- non-opinionated about the source of concurrency (threads, pools, event loops, fibers, actors, etc.) -- async or synchronous execution -- virtual time and schedulers for parameterized concurrency -- test and diagnostic support via test schedulers, test consumers and plugin hooks +- Single dependency: [Reactive-Streams](https://github.com/reactive-streams/reactive-streams-jvm). +- Java 8+ or Android API 21+ required. +- Java 8 lambda-friendly API. +- [Android](https://github.com/ReactiveX/RxAndroid) desugar friendly. +- Fixed API mistakes and many limits of RxJava 2. +- Intended to be a replacement for RxJava 2 with relatively few binary incompatible changes. +- Non-opinionated about the source of concurrency (threads, pools, event loops, fibers, actors, etc.). +- Async or synchronous execution. +- Virtual time and schedulers for parameterized concurrency. +- Test and diagnostic support via test schedulers, test consumers and plugin hooks. +- Interop with newer JDK versions via 3rd party libraries, such as + - [Java 9 Flow API](https://github.com/akarnokd/RxJavaJdk9Interop#rxjavajdk9interop) + - [Java 21 Virtual Threads](https://github.com/akarnokd/RxJavaFiberInterop#rxjavafiberinterop) Learn more about RxJava in general on the Wiki Home. @@ -43,7 +48,7 @@ The first step is to include RxJava 3 into your project, for example, as a Gradl implementation "io.reactivex.rxjava3:rxjava:3.x.y" ``` -(Please replace `x` and `y` with the latest version numbers: [![Maven Central](https://maven-badges.herokuapp.com/maven-central/io.reactivex.rxjava3/rxjava/badge.svg)](https://maven-badges.herokuapp.com/maven-central/io.reactivex.rxjava3/rxjava) +(Please replace `x` and `y` with the latest version numbers: [![Maven Central](https://maven-badges.sml.io/sonatype-central/io.reactivex.rxjava3/rxjava/badge.svg)](https://maven-badges.sml.io/sonatype-central/io.reactivex.rxjava3/rxjava) ) ### Hello World @@ -196,7 +201,7 @@ RxJava operators don't work with `Thread`s or `ExecutorService`s directly but wi - `Schedulers.single()`: Run work on a single thread in a sequential and FIFO manner. - `Schedulers.trampoline()`: Run work in a sequential and FIFO manner in one of the participating threads, usually for testing purposes. -These are available on all JVM platforms but some specific platforms, such as Android, have their own typical `Scheduler`s defined: `AndroidSchedulers.mainThread()`, `SwingScheduler.instance()` or `JavaFXSchedulers.gui()`. +These are available on all JVM platforms but some specific platforms, such as Android, have their own typical `Scheduler`s defined: `AndroidSchedulers.mainThread()`, `SwingScheduler.instance()` or `JavaFXScheduler.platform()`. In addition, there is an option to wrap an existing `Executor` (and its subtypes such as `ExecutorService`) into a `Scheduler` via `Schedulers.from(Executor)`. This can be used, for example, to have a larger but still fixed pool of threads (unlike `computation()` and `io()` respectively). @@ -505,7 +510,7 @@ For further details, consult the [wiki](https://github.com/ReactiveX/RxJava/wiki - Google Group: [RxJava](http://groups.google.com/d/forum/rxjava) - Twitter: [@RxJava](http://twitter.com/RxJava) - [GitHub Issues](https://github.com/ReactiveX/RxJava/issues) -- StackOverflow: [rx-java](http://stackoverflow.com/questions/tagged/rx-java) and [rx-java2](http://stackoverflow.com/questions/tagged/rx-java2) +- StackOverflow: [rx-java](http://stackoverflow.com/questions/tagged/rx-java), [rx-java2](http://stackoverflow.com/questions/tagged/rx-java2) and [rx-java3](http://stackoverflow.com/questions/tagged/rx-java3) - [Gitter.im](https://gitter.im/ReactiveX/RxJava) ## Versioning @@ -566,11 +571,11 @@ and for Ivy: ### Snapshots -Snapshots after May 1st, 2021 are available via https://oss.sonatype.org/content/repositories/snapshots/io/reactivex/rxjava3/rxjava/ +Snapshots after May 19st, 2025 are available via https://central.sonatype.com/repository/maven-snapshots/io/reactivex/rxjava3/rxjava/ ```groovy repositories { - maven { url 'https://oss.sonatype.org/content/repositories/snapshots' } + maven { url 'https://central.sonatype.com/repository/maven-snapshots' } } dependencies { @@ -578,20 +583,7 @@ dependencies { } ``` -Snapshots before May 1st, 2021 are available via https://oss.jfrog.org/libs-snapshot/io/reactivex/rxjava3/rxjava/ -(Note that due to the Sunset of Bintray, our jfrog access has been severed, hence the new snapshot repo above.) - -```groovy -repositories { - maven { url 'https://oss.jfrog.org/libs-snapshot' } -} - -dependencies { - implementation 'io.reactivex.rxjava3:rxjava:3.0.0-SNAPSHOT' -} -``` - -JavaDoc snapshots are available at http://reactivex.io/RxJava/3.x/javadoc/snapshot +JavaDoc snapshots are available at https://reactivex.io/RxJava/3.x/javadoc/snapshot ## Build @@ -626,5 +618,5 @@ For bugs, questions and discussions please use the [Github Issues](https://githu See the License for the specific language governing permissions and limitations under the License. -[beta source link]: https://github.com/ReactiveX/RxJava/blob/3.x/src/main/java/io/reactivex/annotations/Beta.java -[experimental source link]: https://github.com/ReactiveX/RxJava/blob/3.x/src/main/java/io/reactivex/annotations/Experimental.java +[beta source link]: https://github.com/ReactiveX/RxJava/blob/3.x/src/main/java/io/reactivex/rxjava3/annotations/Beta.java +[experimental source link]: https://github.com/ReactiveX/RxJava/blob/3.x/src/main/java/io/reactivex/rxjava3/annotations/Experimental.java diff --git a/SECURITY.md b/SECURITY.md new file mode 100644 index 00000000000..10035743316 --- /dev/null +++ b/SECURITY.md @@ -0,0 +1,7 @@ +# Security Policy + +If you have discovered a security vulnerability in this project, please report it privately. **Do not disclose it as a public issue.** This gives us time to work with you to fix the issue before public exposure, reducing the chance that the exploit will be used before a patch is released. + +Please disclose it at [security advisory](https://github.com/ReactiveX/RxJava/security/advisories/new). + +This project is maintained by a team of volunteers on a reasonable-effort basis. As such, please give us at least 90 days to work on a fix before public exposure. diff --git a/build.gradle b/build.gradle index 993b0eac311..8bcfddb7175 100644 --- a/build.gradle +++ b/build.gradle @@ -4,21 +4,22 @@ plugins { id("eclipse") id("jacoco") id("maven-publish") - id("ru.vyarus.animalsniffer") version "1.5.4" - id("me.champeau.gradle.jmh") version "0.5.3" + id("ru.vyarus.animalsniffer") version "2.0.1" + id("me.champeau.jmh") version "0.7.3" id("com.github.hierynomus.license") version "0.16.1" - id("biz.aQute.bnd.builder") version "6.1.0" - id("com.vanniktech.maven.publish") version "0.18.0" - id("org.beryx.jar") version "1.2.0" + id("biz.aQute.bnd.builder") version "6.4.0" + id("com.vanniktech.maven.publish") version "0.33.0" + id("org.beryx.jar") version "2.0.0" + id("signing") } ext { - reactiveStreamsVersion = "1.0.3" + reactiveStreamsVersion = "1.0.4" junitVersion = "4.13.2" testNgVersion = "7.5" - mockitoVersion = "4.2.0" + mockitoVersion = "4.11.0" jmhLibVersion = "1.21" - guavaVersion = "31.0.1-jre" + guavaVersion = "33.5.0-jre" } def releaseTag = System.getenv("BUILD_TAG") @@ -49,7 +50,16 @@ dependencies { testImplementation "com.google.guava:guava:$guavaVersion" } +def buildWith11 = System.getenv("BUILD_WITH_11") java { + toolchain { + vendor = JvmVendorSpec.ADOPTIUM + if ("true".equals(buildWith11)) { + languageVersion = JavaLanguageVersion.of(11) + } else { + languageVersion = JavaLanguageVersion.of(8) + } + } sourceCompatibility = JavaVersion.VERSION_1_8 targetCompatibility = JavaVersion.VERSION_1_8 } @@ -76,7 +86,7 @@ javadoc { options.links( "https://docs.oracle.com/javase/8/docs/api/", - "http://www.reactive-streams.org/reactive-streams-${reactiveStreamsVersion}-javadoc/" + "https://reactivex.io/RxJava/org.reactivestreams.javadoc/${reactiveStreamsVersion}/" ) finalizedBy javadocCleanup @@ -86,7 +96,20 @@ animalsniffer { annotation = "io.reactivex.rxjava3.internal.util.SuppressAnimalSniffer" } +moduleConfig { + moduleInfoPath = 'src/main/module/module-info.java' + multiReleaseVersion = 9 + version = project.version +} + jar { + from('.') { + include 'LICENSE' + include 'COPYRIGHT' + into('META-INF/') + } + exclude("module-info.class") + // Cover for bnd still not supporting MR Jars: https://github.com/bndtools/bnd/issues/2227 bnd('-fixupmessages': '^Classes found in the wrong directory: \\\\{META-INF/versions/9/module-info\\\\.class=module-info}$') bnd( @@ -100,8 +123,6 @@ jar { "Bundle-SymbolicName": "io.reactivex.rxjava3.rxjava", "Multi-Release": "true" ) - - moduleInfoPath = 'src/main/module/module-info.java' } license { @@ -120,8 +141,8 @@ jmh { jvmArgsAppend = ["-Djmh.separateClasspathJAR=true"] if (project.hasProperty("jmh")) { - include = [".*" + project.jmh + ".*"] - logger.info("JMH: {}", include) + includes = [".*" + project.jmh + ".*"] + logger.info("JMH: {}", includes) } } @@ -160,8 +181,9 @@ jacocoTestReport { dependsOn testNG reports { - xml.enabled = true - html.enabled = true + xml.required.set(true) + csv.required.set(false) + html.required.set(true) } } @@ -173,44 +195,25 @@ checkstyle { "checkstyle.suppressions.file": project.file("config/checkstyle/suppressions.xml"), "checkstyle.header.file" : project.file("config/license/HEADER_JAVA") ] + checkstyleMain.exclude '**/module-info.java' } if (project.hasProperty("releaseMode")) { logger.lifecycle("ReleaseMode: {}", project.releaseMode) - /* - if ("branch" == project.releaseMode) { - - if (version.endsWith("-SNAPSHOT")) { - publishing { - repositories { - maven { - url = "https://s01.oss.sonatype.org/content/repositories/snapshots/" - } - } - } - - mavenPublish { - nexus { - stagingProfile = "io.reactivex" - } - } - } - } - */ if ("full" == project.releaseMode) { signing { if (project.hasProperty("SIGNING_PRIVATE_KEY") && project.hasProperty("SIGNING_PASSWORD")) { useInMemoryPgpKeys(project.getProperty("SIGNING_PRIVATE_KEY"), project.getProperty("SIGNING_PASSWORD")) + sign(publishing.publications) } } - /* - mavenPublish { - nexus { - stagingProfile = "io.reactivex" - } - } - */ + } + mavenPublishing { + // or when publishing to https://central.sonatype.com/ + publishToMavenCentral(com.vanniktech.maven.publish.SonatypeHost.CENTRAL_PORTAL) + + // signAllPublications() } } diff --git a/docs/Additional-Reading.md b/docs/Additional-Reading.md index 85e7d47077e..4badd813085 100644 --- a/docs/Additional-Reading.md +++ b/docs/Additional-Reading.md @@ -3,7 +3,7 @@ A more complete and up-to-date list of resources can be found at the [reactivex. # Introducing Reactive Programming * [Introduction to Rx](http://www.introtorx.com/): a free, on-line book by Lee Campbell **(1.x)** * [The introduction to Reactive Programming you've been missing](https://gist.github.com/staltz/868e7e9bc2a7b8c1f754) by Andre Staltz -* [Mastering Observables](http://docs.couchbase.com/developer/java-2.0/observables.html) from the Couchbase documentation **(1.x)** +* [Mastering Observables](https://docs.huihoo.com/couchbase/developer-guide/java-2.0/observables.html) from the Couchbase documentation **(1.x)** * [Reactive Programming in Java 8 With RxJava](http://pluralsight.com/training/Courses/TableOfContents/reactive-programming-java-8-rxjava), a course designed by Russell Elledge **(1.x)** * [33rd Degree Reactive Java](http://www.slideshare.net/tkowalcz/33rd-degree-reactive-java) by Tomasz Kowalczewski **(1.x)** * [What Every Hipster Should Know About Functional Reactive Programming](http://www.infoq.com/presentations/game-functional-reactive-programming) - Bodil Stokke demos the creation of interactive game mechanics in RxJS diff --git a/docs/Backpressure-(2.0).md b/docs/Backpressure-(2.0).md index 61361d21c4b..6b2f2860af5 100644 --- a/docs/Backpressure-(2.0).md +++ b/docs/Backpressure-(2.0).md @@ -172,7 +172,7 @@ If some of the values can be safely ignored, one can use the sampling (with time } ``` -Note hovewer that these operators only reduce the rate of value reception by the downstream and thus they may still lead to `MissingBackpressureException`. +Note however that these operators only reduce the rate of value reception by the downstream and thus they may still lead to `MissingBackpressureException`. ## onBackpressureBuffer() @@ -229,7 +229,7 @@ Note that the last two strategies cause discontinuity in the stream as they drop ## onBackpressureDrop() -Whenever the downstream is not ready to receive values, this operator will drop that elemenet from the sequence. One can think of it as a 0 capacity `onBackpressureBuffer` with strategy `ON_OVERFLOW_DROP_LATEST`. +Whenever the downstream is not ready to receive values, this operator will drop that element from the sequence. One can think of it as a 0 capacity `onBackpressureBuffer` with strategy `ON_OVERFLOW_DROP_LATEST`. This operator is useful when one can safely ignore values from a source (such as mouse moves or current GPS location signals) as there will be more up-to-date values later on. diff --git a/docs/Filtering-Observables.md b/docs/Filtering-Observables.md index 620800dc8cd..512b69ba8a1 100644 --- a/docs/Filtering-Observables.md +++ b/docs/Filtering-Observables.md @@ -259,7 +259,7 @@ firstOrError.subscribe( **ReactiveX documentation:** [http://reactivex.io/documentation/operators/ignoreelements.html](http://reactivex.io/documentation/operators/ignoreelements.html) -Ignores the single item emitted by a `Single` or `Maybe` source, and returns a `Completable` that signals only the error or completion event from the the source. +Ignores the single item emitted by a `Single` or `Maybe` source, and returns a `Completable` that signals only the error or completion event from the source. ### ignoreElement example diff --git a/docs/Getting-Started.md b/docs/Getting-Started.md index d2ac2e46409..69b69a8ca61 100644 --- a/docs/Getting-Started.md +++ b/docs/Getting-Started.md @@ -66,18 +66,21 @@ You need Java 6 or later. ### Snapshots -Snapshots are available via [JFrog](https://oss.jfrog.org/libs-snapshot/io/reactivex/rxjava3/rxjava/): +Snapshots after May 1st, 2021 are available via https://oss.sonatype.org/content/repositories/snapshots/io/reactivex/rxjava3/rxjava/ ```groovy repositories { - maven { url 'https://oss.jfrog.org/libs-snapshot' } + maven { url 'https://oss.sonatype.org/content/repositories/snapshots' } } dependencies { - compile 'io.reactivex.rxjava3:rxjava:3.0.4' + implementation 'io.reactivex.rxjava3:rxjava:3.0.0-SNAPSHOT' } ``` +JavaDoc snapshots are available at http://reactivex.io/RxJava/3.x/javadoc/snapshot + + ## Building To check out and build the RxJava source, issue the following commands: diff --git a/docs/How-To-Use-RxJava.md b/docs/How-To-Use-RxJava.md index 2d091bdce48..41a46bb75de 100644 --- a/docs/How-To-Use-RxJava.md +++ b/docs/How-To-Use-RxJava.md @@ -285,7 +285,7 @@ onNext => value_14_xform Here is a marble diagram that illustrates this transformation: - + This next example, in Clojure, consumes three asynchronous Observables, including a dependency from one to another, and emits a single response item by combining the items emitted by each of the three Observables with the [`zip`](http://reactivex.io/documentation/operators/zip.html) operator and then transforming the result with [`map`](http://reactivex.io/documentation/operators/map.html): @@ -333,7 +333,7 @@ The response looks like this: And here is a marble diagram that illustrates how that code produces that response: - + The following example, in Groovy, comes from [Ben Christensen’s QCon presentation on the evolution of the Netflix API](https://speakerdeck.com/benjchristensen/evolution-of-the-netflix-api-qcon-sf-2013). It combines two Observables with the [`merge`](http://reactivex.io/documentation/operators/merge.html) operator, then uses the [`reduce`](http://reactivex.io/documentation/operators/reduce.html) operator to construct a single item out of the resulting sequence, then transforms that item with [`map`](http://reactivex.io/documentation/operators/map.html) before emitting it: @@ -350,7 +350,7 @@ public Observable getVideoSummary(APIVideo video) { And here is a marble diagram that illustrates how that code uses the [`reduce`](http://reactivex.io/documentation/operators/reduce.html) operator to bring the results from multiple Observables together in one structure: - + ## Error Handling diff --git a/docs/Phantom-Operators.md b/docs/Phantom-Operators.md index b01ac28ff2c..5193147a228 100644 --- a/docs/Phantom-Operators.md +++ b/docs/Phantom-Operators.md @@ -127,7 +127,7 @@ streamOfItems.flatMap(item -> { itemToObservable(item).subscribeOn(Schedulers.io()); }); ``` -Kick off your work for each item inside [`flatMap`](Transforming-Observables#flatmap-concatmap-and-flatmapiterable) using [`subscribeOn`](Observable-Utility-Operators#subscribeon) to make it asynchronous, or by using a function that already makes asychronous calls. +Kick off your work for each item inside [`flatMap`](Transforming-Observables#flatmap-concatmap-and-flatmapiterable) using [`subscribeOn`](Observable-Utility-Operators#subscribeon) to make it asynchronous, or by using a function that already makes asynchronous calls. #### see also: * RxJava Threading Examples by Graham Lea diff --git a/docs/What's-different-in-2.0.md b/docs/What's-different-in-2.0.md index fac50df56d2..edc681fa7fd 100644 --- a/docs/What's-different-in-2.0.md +++ b/docs/What's-different-in-2.0.md @@ -450,12 +450,12 @@ Before 2.0.7, the operator `strict()` had to be applied in order to achieve the As one of the primary goals of RxJava 2, the design focuses on performance and in order enable it, RxJava 2.0.7 adds a custom `io.reactivex.FlowableSubscriber` interface (extends `org.reactivestreams.Subscriber`) but adds no new methods to it. The new interface is **constrained to RxJava 2** and represents a consumer to `Flowable` that is able to work in a mode that relaxes the Reactive-Streams version 1.0.0 specification in rules §1.3, §2.3, §2.12 and §3.9: - - §1.3 relaxation: `onSubscribe` may run concurrently with `onNext` in case the `FlowableSubscriber` calls `request()` from inside `onSubscribe` and it is the resposibility of `FlowableSubscriber` to ensure thread-safety between the remaining instructions in `onSubscribe` and `onNext`. + - §1.3 relaxation: `onSubscribe` may run concurrently with `onNext` in case the `FlowableSubscriber` calls `request()` from inside `onSubscribe` and it is the responsibility of `FlowableSubscriber` to ensure thread-safety between the remaining instructions in `onSubscribe` and `onNext`. - §2.3 relaxation: calling `Subscription.cancel` and `Subscription.request` from `FlowableSubscriber.onComplete()` or `FlowableSubscriber.onError()` is considered a no-operation. - §2.12 relaxation: if the same `FlowableSubscriber` instance is subscribed to multiple sources, it must ensure its `onXXX` methods remain thread safe. - §3.9 relaxation: issuing a non-positive `request()` will not stop the current stream but signal an error via `RxJavaPlugins.onError`. -From a user's perspective, if one was using the the `subscribe` methods other than `Flowable.subscribe(Subscriber)`, there is no need to do anything regarding this change and there is no extra penalty for it. +From a user's perspective, if one was using the `subscribe` methods other than `Flowable.subscribe(Subscriber)`, there is no need to do anything regarding this change and there is no extra penalty for it. If one was using `Flowable.subscribe(Subscriber)` with the built-in RxJava `Subscriber` implementations such as `DisposableSubscriber`, `TestSubscriber` and `ResourceSubscriber`, there is a small runtime overhead (one `instanceof` check) associated when the code is not recompiled against 2.0.7. diff --git a/docs/Writing-operators-for-2.0.md b/docs/Writing-operators-for-2.0.md index e8486564b1f..1a51664880e 100644 --- a/docs/Writing-operators-for-2.0.md +++ b/docs/Writing-operators-for-2.0.md @@ -565,7 +565,7 @@ Version 2.0.7 introduced a new interface, `FlowableSubscriber` that extends `Sub The rule relaxations are as follows: -- §1.3 relaxation: `onSubscribe` may run concurrently with onNext in case the `FlowableSubscriber` calls `request()` from inside `onSubscribe` and it is the resposibility of `FlowableSubscriber` to ensure thread-safety between the remaining instructions in `onSubscribe` and `onNext`. +- §1.3 relaxation: `onSubscribe` may run concurrently with onNext in case the `FlowableSubscriber` calls `request()` from inside `onSubscribe` and it is the responsibility of `FlowableSubscriber` to ensure thread-safety between the remaining instructions in `onSubscribe` and `onNext`. - §2.3 relaxation: calling `Subscription.cancel` and `Subscription.request` from `FlowableSubscriber.onComplete()` or `FlowableSubscriber.onError()` is considered a no-operation. - §2.12 relaxation: if the same `FlowableSubscriber` instance is subscribed to multiple sources, it must ensure its `onXXX` methods remain thread safe. - §3.9 relaxation: issuing a non-positive `request()` will not stop the current stream but signal an error via `RxJavaPlugins.onError`. diff --git a/gradle/javadoc_cleanup.gradle b/gradle/javadoc_cleanup.gradle index 5f120656e09..63b4f7f0456 100644 --- a/gradle/javadoc_cleanup.gradle +++ b/gradle/javadoc_cleanup.gradle @@ -24,6 +24,12 @@ task javadocCleanup(dependsOn: "javadoc") doLast { fixJavadocFile(rootProject.file('build/docs/javadoc/io/reactivex/rxjava3/plugins/RxJavaPlugins.html')) fixJavadocFile(rootProject.file('build/docs/javadoc/io/reactivex/rxjava3/parallel/ParallelFlowable.html')) + + fixJavadocFile(rootProject.file('build/docs/javadoc/io/reactivex/rxjava3/disposables/Disposable.html')) + + fixJavadocFile(rootProject.file('build/docs/javadoc/io/reactivex/rxjava3/observers/TestObserver.html')) + fixJavadocFile(rootProject.file('build/docs/javadoc/io/reactivex/rxjava3/observers/BaseTestConsumer.html')) + fixJavadocFile(rootProject.file('build/docs/javadoc/io/reactivex/rxjava3/subscribers/TestSubscriber.html')) } def fixJavadocFile(file) { diff --git a/gradle/wrapper/gradle-wrapper.jar b/gradle/wrapper/gradle-wrapper.jar index 7454180f2ae..afba109285a 100644 Binary files a/gradle/wrapper/gradle-wrapper.jar and b/gradle/wrapper/gradle-wrapper.jar differ diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties index 2e6e5897b52..3c44eb1b6f5 100644 --- a/gradle/wrapper/gradle-wrapper.properties +++ b/gradle/wrapper/gradle-wrapper.properties @@ -1,5 +1,6 @@ distributionBase=GRADLE_USER_HOME distributionPath=wrapper/dists -distributionUrl=https\://services.gradle.org/distributions/gradle-7.3.3-bin.zip +distributionUrl=https\://services.gradle.org/distributions/gradle-8.14-bin.zip +networkTimeout=10000 zipStoreBase=GRADLE_USER_HOME zipStorePath=wrapper/dists diff --git a/gradlew b/gradlew index c53aefaa5fc..65dcd68d65c 100755 --- a/gradlew +++ b/gradlew @@ -1,7 +1,7 @@ #!/bin/sh # -# Copyright 2015-2021 the original authors. +# Copyright © 2015-2021 the original authors. # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. @@ -32,10 +32,10 @@ # Busybox and similar reduced shells will NOT work, because this script # requires all of these POSIX shell features: # * functions; -# * expansions $var, ${var}, ${var:-default}, ${var+SET}, -# ${var#prefix}, ${var%suffix}, and $( cmd ); -# * compound commands having a testable exit status, especially case; -# * various built-in commands including command, set, and ulimit. +# * expansions «$var», «${var}», «${var:-default}», «${var+SET}», +# «${var#prefix}», «${var%suffix}», and «$( cmd )»; +# * compound commands having a testable exit status, especially «case»; +# * various built-in commands including «command», «set», and «ulimit». # # Important for patching: # @@ -55,7 +55,7 @@ # Darwin, MinGW, and NonStop. # # (3) This script is generated from the Groovy template -# https://github.com/gradle/gradle/blob/master/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt +# https://github.com/gradle/gradle/blob/HEAD/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt # within the Gradle project. # # You can find Gradle at https://github.com/gradle/gradle/. @@ -80,10 +80,10 @@ do esac done -APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit - -APP_NAME="Gradle" +# This is normally unused +# shellcheck disable=SC2034 APP_BASE_NAME=${0##*/} +APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit # Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script. DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"' @@ -143,12 +143,16 @@ fi if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then case $MAX_FD in #( max*) + # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked. + # shellcheck disable=SC3045 MAX_FD=$( ulimit -H -n ) || warn "Could not query maximum file descriptor limit" esac case $MAX_FD in #( '' | soft) :;; #( *) + # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked. + # shellcheck disable=SC3045 ulimit -n "$MAX_FD" || warn "Could not set maximum file descriptor limit to $MAX_FD" esac @@ -205,6 +209,12 @@ set -- \ org.gradle.wrapper.GradleWrapperMain \ "$@" +# Stop when "xargs" is not available. +if ! command -v xargs >/dev/null 2>&1 +then + die "xargs is not available" +fi + # Use "xargs" to parse quoted args. # # With -n1 it outputs one arg per line, with the quotes and backslashes removed. diff --git a/gradlew.bat b/gradlew.bat index 107acd32c4e..93e3f59f135 100644 --- a/gradlew.bat +++ b/gradlew.bat @@ -14,7 +14,7 @@ @rem limitations under the License. @rem -@if "%DEBUG%" == "" @echo off +@if "%DEBUG%"=="" @echo off @rem ########################################################################## @rem @rem Gradle startup script for Windows @@ -25,7 +25,8 @@ if "%OS%"=="Windows_NT" setlocal set DIRNAME=%~dp0 -if "%DIRNAME%" == "" set DIRNAME=. +if "%DIRNAME%"=="" set DIRNAME=. +@rem This is normally unused set APP_BASE_NAME=%~n0 set APP_HOME=%DIRNAME% @@ -40,7 +41,7 @@ if defined JAVA_HOME goto findJavaFromJavaHome set JAVA_EXE=java.exe %JAVA_EXE% -version >NUL 2>&1 -if "%ERRORLEVEL%" == "0" goto execute +if %ERRORLEVEL% equ 0 goto execute echo. echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH. @@ -75,13 +76,15 @@ set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar :end @rem End local scope for the variables with windows NT shell -if "%ERRORLEVEL%"=="0" goto mainEnd +if %ERRORLEVEL% equ 0 goto mainEnd :fail rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of rem the _cmd.exe /c_ return code! -if not "" == "%GRADLE_EXIT_CONSOLE%" exit 1 -exit /b 1 +set EXIT_CODE=%ERRORLEVEL% +if %EXIT_CODE% equ 0 set EXIT_CODE=1 +if not ""=="%GRADLE_EXIT_CONSOLE%" exit %EXIT_CODE% +exit /b %EXIT_CODE% :mainEnd if "%OS%"=="Windows_NT" endlocal diff --git a/src/jmh/java/io/reactivex/rxjava3/core/BinaryFlatMapPerf.java b/src/jmh/java/io/reactivex/rxjava3/core/BinaryFlatMapPerf.java index c4a0a385a51..6e6ae7e3c62 100644 --- a/src/jmh/java/io/reactivex/rxjava3/core/BinaryFlatMapPerf.java +++ b/src/jmh/java/io/reactivex/rxjava3/core/BinaryFlatMapPerf.java @@ -139,9 +139,9 @@ public Observable apply(Integer v) { } }); - singleFlatMapHideObservable = Single.just(1).flatMapObservable(new Function>() { + singleFlatMapHideObservable = Single.just(1).flatMapObservable(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return arrayObservableHide; } }); @@ -153,16 +153,16 @@ public Iterable apply(Integer v) { } }); - maybeFlatMapObservable = Maybe.just(1).flatMapObservable(new Function>() { + maybeFlatMapObservable = Maybe.just(1).flatMapObservable(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return arrayObservable; } }); - maybeFlatMapHideObservable = Maybe.just(1).flatMapObservable(new Function>() { + maybeFlatMapHideObservable = Maybe.just(1).flatMapObservable(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return arrayObservableHide; } }); diff --git a/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableConcatMapMaybePerf.java b/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableConcatMapMaybePerf.java index 87ee5a07e4c..4310ea2e955 100644 --- a/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableConcatMapMaybePerf.java +++ b/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableConcatMapMaybePerf.java @@ -60,9 +60,9 @@ public Publisher apply(Integer v) { } }); - flowableDedicated = source.concatMapMaybe(new Function>() { + flowableDedicated = source.concatMapMaybe(new Function>() { @Override - public Maybe apply(Integer v) { + public Maybe apply(Integer v) { return Maybe.just(v); } }); diff --git a/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableFlatMapMaybeEmptyPerf.java b/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableFlatMapMaybeEmptyPerf.java index 8ab19a00c68..699f76c0743 100644 --- a/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableFlatMapMaybeEmptyPerf.java +++ b/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableFlatMapMaybeEmptyPerf.java @@ -60,9 +60,9 @@ public Publisher apply(Integer v) { } }); - flowableDedicated = source.flatMapMaybe(new Function>() { + flowableDedicated = source.flatMapMaybe(new Function>() { @Override - public Maybe apply(Integer v) { + public Maybe apply(Integer v) { return Maybe.empty(); } }); diff --git a/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableFlatMapMaybePerf.java b/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableFlatMapMaybePerf.java index d0f3730b42a..f81ed10ec33 100644 --- a/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableFlatMapMaybePerf.java +++ b/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableFlatMapMaybePerf.java @@ -60,9 +60,9 @@ public Publisher apply(Integer v) { } }); - flowableDedicated = source.flatMapMaybe(new Function>() { + flowableDedicated = source.flatMapMaybe(new Function>() { @Override - public Maybe apply(Integer v) { + public Maybe apply(Integer v) { return Maybe.just(v); } }); diff --git a/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableFlatMapSinglePerf.java b/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableFlatMapSinglePerf.java index 4f509386474..5a92bf20ffb 100644 --- a/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableFlatMapSinglePerf.java +++ b/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableFlatMapSinglePerf.java @@ -60,9 +60,9 @@ public Publisher apply(Integer v) { } }); - flowableDedicated = source.flatMapSingle(new Function>() { + flowableDedicated = source.flatMapSingle(new Function>() { @Override - public Single apply(Integer v) { + public Single apply(Integer v) { return Single.just(v); } }); diff --git a/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableSwitchMapMaybeEmptyPerf.java b/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableSwitchMapMaybeEmptyPerf.java index 83ad00e0f9e..46ce694f6dd 100644 --- a/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableSwitchMapMaybeEmptyPerf.java +++ b/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableSwitchMapMaybeEmptyPerf.java @@ -60,9 +60,9 @@ public Publisher apply(Integer v) { } }); - flowableDedicated = source.switchMapMaybe(new Function>() { + flowableDedicated = source.switchMapMaybe(new Function>() { @Override - public Maybe apply(Integer v) { + public Maybe apply(Integer v) { return Maybe.empty(); } }); diff --git a/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableSwitchMapMaybePerf.java b/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableSwitchMapMaybePerf.java index e36b49c4d3a..e96bbc39194 100644 --- a/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableSwitchMapMaybePerf.java +++ b/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableSwitchMapMaybePerf.java @@ -60,9 +60,9 @@ public Publisher apply(Integer v) { } }); - flowableDedicated = source.switchMapMaybe(new Function>() { + flowableDedicated = source.switchMapMaybe(new Function>() { @Override - public Maybe apply(Integer v) { + public Maybe apply(Integer v) { return Maybe.just(v); } }); diff --git a/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableSwitchMapSinglePerf.java b/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableSwitchMapSinglePerf.java index 0da69418955..ef06ebfa668 100644 --- a/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableSwitchMapSinglePerf.java +++ b/src/jmh/java/io/reactivex/rxjava3/xmapz/FlowableSwitchMapSinglePerf.java @@ -60,9 +60,9 @@ public Publisher apply(Integer v) { } }); - flowableDedicated = source.switchMapSingle(new Function>() { + flowableDedicated = source.switchMapSingle(new Function>() { @Override - public Single apply(Integer v) { + public Single apply(Integer v) { return Single.just(v); } }); diff --git a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableConcatMapCompletablePerf.java b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableConcatMapCompletablePerf.java index 48b20dc005f..2229eed77a9 100644 --- a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableConcatMapCompletablePerf.java +++ b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableConcatMapCompletablePerf.java @@ -45,16 +45,16 @@ public void setup() { Observable source = Observable.fromArray(sourceArray); - observablePlain = source.concatMap(new Function>() { + observablePlain = source.concatMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Observable.empty(); } }); - observableConvert = source.concatMap(new Function>() { + observableConvert = source.concatMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Completable.complete().toObservable(); } }); diff --git a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableConcatMapMaybeEmptyPerf.java b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableConcatMapMaybeEmptyPerf.java index 4528c90b506..cfde5183e5f 100644 --- a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableConcatMapMaybeEmptyPerf.java +++ b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableConcatMapMaybeEmptyPerf.java @@ -45,23 +45,23 @@ public void setup() { Observable source = Observable.fromArray(sourceArray); - observablePlain = source.concatMap(new Function>() { + observablePlain = source.concatMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Observable.empty(); } }); - concatMapToObservableEmpty = source.concatMap(new Function>() { + concatMapToObservableEmpty = source.concatMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Maybe.empty().toObservable(); } }); - observableDedicated = source.concatMapMaybe(new Function>() { + observableDedicated = source.concatMapMaybe(new Function>() { @Override - public Maybe apply(Integer v) { + public Maybe apply(Integer v) { return Maybe.empty(); } }); diff --git a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableConcatMapMaybePerf.java b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableConcatMapMaybePerf.java index 204020abfe8..75e75067245 100644 --- a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableConcatMapMaybePerf.java +++ b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableConcatMapMaybePerf.java @@ -45,23 +45,23 @@ public void setup() { Observable source = Observable.fromArray(sourceArray); - observablePlain = source.concatMap(new Function>() { + observablePlain = source.concatMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Observable.just(v); } }); - observableConvert = source.concatMap(new Function>() { + observableConvert = source.concatMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Maybe.just(v).toObservable(); } }); - observableDedicated = source.concatMapMaybe(new Function>() { + observableDedicated = source.concatMapMaybe(new Function>() { @Override - public Maybe apply(Integer v) { + public Maybe apply(Integer v) { return Maybe.just(v); } }); diff --git a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableConcatMapSinglePerf.java b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableConcatMapSinglePerf.java index e2e34b24f56..4227791222b 100644 --- a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableConcatMapSinglePerf.java +++ b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableConcatMapSinglePerf.java @@ -45,23 +45,23 @@ public void setup() { Observable source = Observable.fromArray(sourceArray); - observablePlain = source.concatMap(new Function>() { + observablePlain = source.concatMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Observable.just(v); } }); - observableConvert = source.concatMap(new Function>() { + observableConvert = source.concatMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Single.just(v).toObservable(); } }); - observableDedicated = source.concatMapSingle(new Function>() { + observableDedicated = source.concatMapSingle(new Function>() { @Override - public Single apply(Integer v) { + public Single apply(Integer v) { return Single.just(v); } }); diff --git a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableFlatMapCompletablePerf.java b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableFlatMapCompletablePerf.java index b6daa57eb6d..6a916a68f1e 100644 --- a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableFlatMapCompletablePerf.java +++ b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableFlatMapCompletablePerf.java @@ -45,16 +45,16 @@ public void setup() { Observable source = Observable.fromArray(sourceArray); - observablePlain = source.flatMap(new Function>() { + observablePlain = source.flatMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Observable.empty(); } }); - observableConvert = source.flatMap(new Function>() { + observableConvert = source.flatMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Completable.complete().toObservable(); } }); diff --git a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableFlatMapMaybeEmptyPerf.java b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableFlatMapMaybeEmptyPerf.java index 5d0327fa466..377a8bba933 100644 --- a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableFlatMapMaybeEmptyPerf.java +++ b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableFlatMapMaybeEmptyPerf.java @@ -45,23 +45,23 @@ public void setup() { Observable source = Observable.fromArray(sourceArray); - observablePlain = source.flatMap(new Function>() { + observablePlain = source.flatMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Observable.empty(); } }); - observableConvert = source.flatMap(new Function>() { + observableConvert = source.flatMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Maybe.empty().toObservable(); } }); - observableDedicated = source.flatMapMaybe(new Function>() { + observableDedicated = source.flatMapMaybe(new Function>() { @Override - public Maybe apply(Integer v) { + public Maybe apply(Integer v) { return Maybe.empty(); } }); diff --git a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableFlatMapMaybePerf.java b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableFlatMapMaybePerf.java index e2a7c43bea5..248ca981126 100644 --- a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableFlatMapMaybePerf.java +++ b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableFlatMapMaybePerf.java @@ -45,23 +45,23 @@ public void setup() { Observable source = Observable.fromArray(sourceArray); - observablePlain = source.flatMap(new Function>() { + observablePlain = source.flatMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Observable.just(v); } }); - observableConvert = source.flatMap(new Function>() { + observableConvert = source.flatMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Maybe.just(v).toObservable(); } }); - observableDedicated = source.flatMapMaybe(new Function>() { + observableDedicated = source.flatMapMaybe(new Function>() { @Override - public Maybe apply(Integer v) { + public Maybe apply(Integer v) { return Maybe.just(v); } }); diff --git a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableFlatMapSinglePerf.java b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableFlatMapSinglePerf.java index add0cd310c6..880da95f5a1 100644 --- a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableFlatMapSinglePerf.java +++ b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableFlatMapSinglePerf.java @@ -45,23 +45,23 @@ public void setup() { Observable source = Observable.fromArray(sourceArray); - observablePlain = source.flatMap(new Function>() { + observablePlain = source.flatMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Observable.just(v); } }); - observableConvert = source.flatMap(new Function>() { + observableConvert = source.flatMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Single.just(v).toObservable(); } }); - observableDedicated = source.flatMapSingle(new Function>() { + observableDedicated = source.flatMapSingle(new Function>() { @Override - public Single apply(Integer v) { + public Single apply(Integer v) { return Single.just(v); } }); diff --git a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableSwitchMapCompletablePerf.java b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableSwitchMapCompletablePerf.java index 69b8e71f184..41964c3dbde 100644 --- a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableSwitchMapCompletablePerf.java +++ b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableSwitchMapCompletablePerf.java @@ -45,16 +45,16 @@ public void setup() { Observable source = Observable.fromArray(sourceArray); - observablePlain = source.switchMap(new Function>() { + observablePlain = source.switchMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Observable.empty(); } }); - observableConvert = source.switchMap(new Function>() { + observableConvert = source.switchMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Completable.complete().toObservable(); } }); diff --git a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableSwitchMapMaybeEmptyPerf.java b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableSwitchMapMaybeEmptyPerf.java index 3930534eb8e..6a4ea5c73bd 100644 --- a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableSwitchMapMaybeEmptyPerf.java +++ b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableSwitchMapMaybeEmptyPerf.java @@ -45,23 +45,23 @@ public void setup() { Observable source = Observable.fromArray(sourceArray); - observablePlain = source.switchMap(new Function>() { + observablePlain = source.switchMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Observable.empty(); } }); - observableConvert = source.switchMap(new Function>() { + observableConvert = source.switchMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Maybe.empty().toObservable(); } }); - observableDedicated = source.switchMapMaybe(new Function>() { + observableDedicated = source.switchMapMaybe(new Function>() { @Override - public Maybe apply(Integer v) { + public Maybe apply(Integer v) { return Maybe.empty(); } }); diff --git a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableSwitchMapMaybePerf.java b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableSwitchMapMaybePerf.java index 30158d012d1..f0c32858904 100644 --- a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableSwitchMapMaybePerf.java +++ b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableSwitchMapMaybePerf.java @@ -45,23 +45,23 @@ public void setup() { Observable source = Observable.fromArray(sourceArray); - observablePlain = source.switchMap(new Function>() { + observablePlain = source.switchMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Observable.just(v); } }); - observableConvert = source.switchMap(new Function>() { + observableConvert = source.switchMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Maybe.just(v).toObservable(); } }); - observableDedicated = source.switchMapMaybe(new Function>() { + observableDedicated = source.switchMapMaybe(new Function>() { @Override - public Maybe apply(Integer v) { + public Maybe apply(Integer v) { return Maybe.just(v); } }); diff --git a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableSwitchMapSinglePerf.java b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableSwitchMapSinglePerf.java index 75aeb504f93..087f32c8e36 100644 --- a/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableSwitchMapSinglePerf.java +++ b/src/jmh/java/io/reactivex/rxjava3/xmapz/ObservableSwitchMapSinglePerf.java @@ -45,23 +45,23 @@ public void setup() { Observable source = Observable.fromArray(sourceArray); - observablePlain = source.switchMap(new Function>() { + observablePlain = source.switchMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Observable.just(v); } }); - observableConvert = source.switchMap(new Function>() { + observableConvert = source.switchMap(new Function>() { @Override - public Observable apply(Integer v) { + public Observable apply(Integer v) { return Single.just(v).toObservable(); } }); - observableDedicated = source.switchMapSingle(new Function>() { + observableDedicated = source.switchMapSingle(new Function>() { @Override - public Single apply(Integer v) { + public Single apply(Integer v) { return Single.just(v); } }); diff --git a/src/main/java/io/reactivex/rxjava3/core/Completable.java b/src/main/java/io/reactivex/rxjava3/core/Completable.java index 910c7a2fc94..e31a44c32c3 100644 --- a/src/main/java/io/reactivex/rxjava3/core/Completable.java +++ b/src/main/java/io/reactivex/rxjava3/core/Completable.java @@ -479,7 +479,7 @@ public static Completable unsafeCreate(@NonNull CompletableSource onSubscribe) { @CheckReturnValue @NonNull @SchedulerSupport(SchedulerSupport.NONE) - public static Completable defer(@NonNull Supplier supplier) { + public static Completable defer(@NonNull Supplier supplier) { Objects.requireNonNull(supplier, "supplier is null"); return RxJavaPlugins.onAssembly(new CompletableDefer(supplier)); } @@ -503,7 +503,7 @@ public static Completable defer(@NonNull Supplier s @CheckReturnValue @NonNull @SchedulerSupport(SchedulerSupport.NONE) - public static Completable error(@NonNull Supplier supplier) { + public static Completable error(@NonNull Supplier supplier) { Objects.requireNonNull(supplier, "supplier is null"); return RxJavaPlugins.onAssembly(new CompletableErrorSupplier(supplier)); } @@ -601,6 +601,7 @@ public static Completable fromCallable(@NonNull Callable callable) { * @param future the {@code Future} to react to * @return the new {@code Completable} instance * @throws NullPointerException if {@code future} is {@code null} + * @see #fromCompletionStage(CompletionStage) */ @CheckReturnValue @NonNull @@ -3410,7 +3411,7 @@ public final TestObserver test(boolean dispose) { * *

* Note that the operator takes an already instantiated, running or terminated {@code CompletionStage}. - * If the optional is to be created per consumer upon subscription, use {@link #defer(Supplier)} + * If the {@code CompletionStage} is to be created per consumer upon subscription, use {@link #defer(Supplier)} * around {@code fromCompletionStage}: * 


      * Maybe.defer(() -> Completable.fromCompletionStage(createCompletionStage()));
diff --git a/src/main/java/io/reactivex/rxjava3/core/Flowable.java b/src/main/java/io/reactivex/rxjava3/core/Flowable.java
index 6cbdf0a4124..39f3c63b43b 100644
--- a/src/main/java/io/reactivex/rxjava3/core/Flowable.java
+++ b/src/main/java/io/reactivex/rxjava3/core/Flowable.java
@@ -2040,7 +2040,7 @@ public static int bufferSize() {
     @NonNull
     @BackpressureSupport(BackpressureKind.PASS_THROUGH)
     @SchedulerSupport(SchedulerSupport.NONE)
-    public static <@NonNull T> Flowable defer(@NonNull Supplier> supplier) {
+    public static <@NonNull T> Flowable defer(@NonNull Supplier> supplier) {
         Objects.requireNonNull(supplier, "supplier is null");
         return RxJavaPlugins.onAssembly(new FlowableDefer<>(supplier));
     }
@@ -2095,7 +2095,7 @@ public static int bufferSize() {
     @NonNull
     @BackpressureSupport(BackpressureKind.PASS_THROUGH)
     @SchedulerSupport(SchedulerSupport.NONE)
-    public static <@NonNull T> Flowable error(@NonNull Supplier supplier) {
+    public static <@NonNull T> Flowable error(@NonNull Supplier supplier) {
         Objects.requireNonNull(supplier, "supplier is null");
         return RxJavaPlugins.onAssembly(new FlowableError<>(supplier));
     }
@@ -7475,8 +7475,10 @@ public final Flowable cacheWithInitialCapacity(int initialCapacity) {
     }
 
     /**
-     * Returns a {@code Flowable} that emits the items emitted by the current {@code Flowable}, converted to the specified
-     * type.
+     * Returns a {@code Flowable} that emits the upstream items while
+     * they can be cast via {@link Class#cast(Object)} until the upstream terminates,
+     * or until the upstream signals an item which can't be cast,
+     * resulting in a {@link ClassCastException} to be signaled to the downstream.
      * 

      * 
      * 

@@ -7489,8 +7491,7 @@ public final Flowable cacheWithInitialCapacity(int initialCapacity) {
      *
      * @param  the output value type cast to
      * @param clazz
-     *            the target class type that {@code cast} will cast the items emitted by the current {@code Flowable}
-     *            into before emitting them from the resulting {@code Flowable}
+     *            the target class to use to try and cast the upstream items into
      * @return the new {@code Flowable} instance
      * @throws NullPointerException if {@code clazz} is {@code null}
      * @see ReactiveX operators documentation: Map
@@ -8265,7 +8266,7 @@ public final Completable concatMapCompletableDelayError(@NonNull Function
-     * 
+     * 
      * 

      *  
Backpressure:

      *  
The operator expects the upstream to support backpressure and honors
@@ -8298,7 +8299,7 @@ public final Completable concatMapCompletableDelayError(@NonNull Function
-     * 
+     * 
      * 

      *  
Backpressure:

      *  
The operator expects the upstream to support backpressure and honors
@@ -8338,7 +8339,7 @@ public final Completable concatMapCompletableDelayError(@NonNull Function
-     * 
+     * 
      * 

      *  
Backpressure:

      *  
The operator expects the upstream to support backpressure and honors
@@ -8371,7 +8372,7 @@ public final Completable concatMapCompletableDelayError(@NonNull Function
-     * 
+     * 
      * 

      *  
Backpressure:

      *  
The operator expects the upstream to support backpressure and honors
@@ -8410,7 +8411,7 @@ public final Completable concatMapCompletableDelayError(@NonNull Function
-     * 
+     * 
      * 

      *  
Backpressure:

      *  
The operator expects the upstream to support backpressure and honors
@@ -8455,7 +8456,7 @@ public final Completable concatMapCompletableDelayError(@NonNull Function
-     * 
+     * 
      * 

      *  
Backpressure:

      *  
The operator expects the upstream to support backpressure and honors
@@ -8488,7 +8489,7 @@ public final Completable concatMapCompletableDelayError(@NonNull Function
-     * 
+     * 
      * 

      *  
Backpressure:

      *  
The operator expects the upstream to support backpressure and honors
@@ -8528,7 +8529,7 @@ public final Completable concatMapCompletableDelayError(@NonNull Function
-     * 
+     * 
      * 

      *  
Backpressure:

      *  
The operator expects the upstream to support backpressure and honors
@@ -8561,7 +8562,7 @@ public final Completable concatMapCompletableDelayError(@NonNull Function
-     * 
+     * 
      * 

      *  
Backpressure:

      *  
The operator expects the upstream to support backpressure and honors
@@ -8600,7 +8601,7 @@ public final Completable concatMapCompletableDelayError(@NonNull Function
-     * 
+     * 
      * 

      *  
Backpressure:

      *  
The operator expects the upstream to support backpressure and honors
@@ -8930,7 +8931,59 @@ public final Flowable debounce(long timeout, @NonNull TimeUnit unit) {
     public final Flowable debounce(long timeout, @NonNull TimeUnit unit, @NonNull Scheduler scheduler) {
         Objects.requireNonNull(unit, "unit is null");
         Objects.requireNonNull(scheduler, "scheduler is null");
-        return RxJavaPlugins.onAssembly(new FlowableDebounceTimed<>(this, timeout, unit, scheduler));
+        return RxJavaPlugins.onAssembly(new FlowableDebounceTimed<>(this, timeout, unit, scheduler, null));
+    }
+
+    /**
+     * Returns a {@code Flowable} that mirrors the current {@code Flowable}, except that it drops items emitted by the
+     * current {@code Flowable} that are followed by newer items before a timeout value expires on a specified
+     * {@link Scheduler}. The timer resets on each emission.
+     * 

+     * Note: If items keep being emitted by the current {@code Flowable} faster than the timeout then no items
+     * will be emitted by the resulting {@code Flowable}.
+     * 

+     * 
+     * 

+     * Delivery of the item after the grace period happens on the given {@code Scheduler}'s
+     * {@code Worker} which if takes too long, a newer item may arrive from the upstream, causing the
+     * {@code Worker}'s task to get disposed, which may also interrupt any downstream blocking operation
+     * (yielding an {@code InterruptedException}). It is recommended processing items
+     * that may take long time to be moved to another thread via {@link #observeOn} applied after
+     * {@code debounce} itself.
+     * 

+     *  
Backpressure:

+     *  
This operator does not support backpressure as it uses time to control data flow.

+     *  
Scheduler:

+     *  
You specify which {@code Scheduler} this operator will use.

+     * 

+     *
+     * @param timeout
+     *            the time each item has to be "the most recent" of those emitted by the current {@code Flowable} to
+     *            ensure that it's not dropped
+     * @param unit
+     *            the unit of time for the specified {@code timeout}
+     * @param scheduler
+     *            the {@code Scheduler} to use internally to manage the timers that handle the timeout for each
+     *            item
+     * @param onDropped
+     *            called with the current entry when it has been replaced by a new one
+     * @return the new {@code Flowable} instance
+     * @throws NullPointerException if {@code unit} or {@code scheduler} is {@code null} or {@code onDropped} is {@code null}
+     * @see ReactiveX operators documentation: Debounce
+     * @see RxJava wiki: Backpressure
+     * @see #throttleWithTimeout(long, TimeUnit, Scheduler, Consumer)
+     * @since 3.1.6 - Experimental
+     */
+    @CheckReturnValue
+    @NonNull
+    @BackpressureSupport(BackpressureKind.ERROR)
+    @SchedulerSupport(SchedulerSupport.CUSTOM)
+    @Experimental
+    public final Flowable debounce(long timeout, @NonNull TimeUnit unit, @NonNull Scheduler scheduler, @NonNull Consumer onDropped) {
+        Objects.requireNonNull(unit, "unit is null");
+        Objects.requireNonNull(scheduler, "scheduler is null");
+        Objects.requireNonNull(onDropped, "onDropped is null");
+        return RxJavaPlugins.onAssembly(new FlowableDebounceTimed<>(this, timeout, unit, scheduler, onDropped));
     }
 
     /**
@@ -10148,7 +10201,7 @@ public final Maybe firstElement() {
      * Returns a {@link Single} that emits only the very first item emitted by this {@code Flowable}, or a default
      * item if this {@code Flowable} completes without emitting anything.
      * 

-     * 
+     * 
      * 

      *  
Backpressure:

      *  
The operator honors backpressure from downstream and consumes the current {@code Flowable} in a bounded manner.

@@ -10904,6 +10957,8 @@ public final Completable flatMapCompletable(@NonNull Function
+     * 
      * 

      *  
Backpressure:

      *  
The operator consumes the upstream in an unbounded manner.

@@ -10927,6 +10982,8 @@ public final Completable flatMapCompletable(@NonNull Function
+     * 
      * 

      *  
Backpressure:

      *  
If {@code maxConcurrency == }{@link Integer#MAX_VALUE} the operator consumes the upstream in an unbounded manner.
@@ -12494,7 +12551,7 @@ public final Flowable onBackpressureBuffer(int capacity, boolean delayError)
     @NonNull
     public final Flowable onBackpressureBuffer(int capacity, boolean delayError, boolean unbounded) {
         ObjectHelper.verifyPositive(capacity, "capacity");
-        return RxJavaPlugins.onAssembly(new FlowableOnBackpressureBuffer<>(this, capacity, unbounded, delayError, Functions.EMPTY_ACTION));
+        return RxJavaPlugins.onAssembly(new FlowableOnBackpressureBuffer<>(this, capacity, unbounded, delayError, Functions.EMPTY_ACTION, Functions.emptyConsumer()));
     }
 
     /**
@@ -12525,6 +12582,7 @@ public final Flowable onBackpressureBuffer(int capacity, boolean delayError,
      * @throws NullPointerException if {@code onOverflow} is {@code null}
      * @throws IllegalArgumentException if {@code capacity} is non-positive
      * @see ReactiveX operators documentation: backpressure operators
+     * @see #onBackpressureBuffer(int, boolean, boolean, Action, Consumer)
      * @since 1.1.0
      */
     @CheckReturnValue
@@ -12535,7 +12593,51 @@ public final Flowable onBackpressureBuffer(int capacity, boolean delayError,
             @NonNull Action onOverflow) {
         Objects.requireNonNull(onOverflow, "onOverflow is null");
         ObjectHelper.verifyPositive(capacity, "capacity");
-        return RxJavaPlugins.onAssembly(new FlowableOnBackpressureBuffer<>(this, capacity, unbounded, delayError, onOverflow));
+        return RxJavaPlugins.onAssembly(new FlowableOnBackpressureBuffer<>(this, capacity, unbounded, delayError, onOverflow, Functions.emptyConsumer()));
+    }
+
+    /**
+     * Buffers an optionally unlimited number of items from the current {@code Flowable} and allows it to emit as fast it can while allowing the
+     * downstream to consume the items at its own place.
+     * If {@code unbounded} is {@code true}, the resulting {@code Flowable} will signal a
+     * {@link MissingBackpressureException} via {@code onError} as soon as the buffer's capacity is exceeded, dropping all undelivered
+     * items, canceling the flow and calling the {@code onOverflow} action.
+     * 

+     * 
+     * 

+     *  
Backpressure:

+     *  
The operator honors backpressure from downstream and consumes the current {@code Flowable} in an unbounded
+     *  manner (i.e., not applying backpressure to it).

+     *  
Scheduler:

+     *  
{@code onBackpressureBuffer} does not operate by default on a particular {@link Scheduler}.

+     * 

+     *
+     * @param capacity number of slots available in the buffer.
+     * @param delayError
+     *                if {@code true}, an exception from the current {@code Flowable} is delayed until all buffered elements have been
+     *                consumed by the downstream; if {@code false}, an exception is immediately signaled to the downstream, skipping
+     *                any buffered element
+     * @param unbounded
+     *                if {@code true}, the capacity value is interpreted as the internal "island" size of the unbounded buffer
+     * @param onOverflow action to execute if an item needs to be buffered, but there are no available slots.
+     * @param onDropped the {@link Consumer} to be called with the item that could not be buffered due to capacity constraints.
+     * @return the new {@code Flowable} instance
+     * @throws NullPointerException if {@code onOverflow} or {@code onDropped} is {@code null}
+     * @throws IllegalArgumentException if {@code capacity} is non-positive
+     * @see ReactiveX operators documentation: backpressure operators
+     * @since 3.1.7
+     */
+    @CheckReturnValue
+    @NonNull
+    @BackpressureSupport(BackpressureKind.SPECIAL)
+    @SchedulerSupport(SchedulerSupport.NONE)
+    @Experimental
+    public final Flowable onBackpressureBuffer(int capacity, boolean delayError, boolean unbounded,
+            @NonNull Action onOverflow, @NonNull Consumer onDropped) {
+        Objects.requireNonNull(onOverflow, "onOverflow is null");
+        Objects.requireNonNull(onDropped, "onDropped is null");
+        ObjectHelper.verifyPositive(capacity, "capacity");
+        return RxJavaPlugins.onAssembly(new FlowableOnBackpressureBuffer<>(this, capacity, unbounded, delayError, onOverflow, onDropped));
     }
 
     /**
@@ -12601,6 +12703,7 @@ public final Flowable onBackpressureBuffer(int capacity, @NonNull Action onOv
      * @throws NullPointerException if {@code onOverflow} or {@code overflowStrategy} is {@code null}
      * @throws IllegalArgumentException if {@code capacity} is non-positive
      * @see ReactiveX operators documentation: backpressure operators
+     * @see #onBackpressureBuffer(long, Action, BackpressureOverflowStrategy)
      * @since 2.0
      */
     @CheckReturnValue
@@ -12610,9 +12713,55 @@ public final Flowable onBackpressureBuffer(int capacity, @NonNull Action onOv
     public final Flowable onBackpressureBuffer(long capacity, @Nullable Action onOverflow, @NonNull BackpressureOverflowStrategy overflowStrategy) {
         Objects.requireNonNull(overflowStrategy, "overflowStrategy is null");
         ObjectHelper.verifyPositive(capacity, "capacity");
-        return RxJavaPlugins.onAssembly(new FlowableOnBackpressureBufferStrategy<>(this, capacity, onOverflow, overflowStrategy));
+        return RxJavaPlugins.onAssembly(new FlowableOnBackpressureBufferStrategy<>(this, capacity, onOverflow, overflowStrategy, null));
     }
 
+    /**
+     * Buffers an optionally unlimited number of items from the current {@code Flowable} and allows it to emit as fast it can while allowing the
+     * downstream to consume the items at its own place.
+     * The resulting {@code Flowable} will behave as determined by {@code overflowStrategy} if the buffer capacity is exceeded:
+     * 
    
+     *     
  • {@link BackpressureOverflowStrategy#ERROR} (default) will call {@code onError} dropping all undelivered items,
+     *     canceling the source, and notifying the producer with {@code onOverflow}. 
    • 
+     *     
  • {@link BackpressureOverflowStrategy#DROP_LATEST} will drop any new items emitted by the producer while
+     *     the buffer is full, without generating any {@code onError}.  Each drop will, however, invoke {@code onOverflow}
+     *     to signal the overflow to the producer.
    • 
+     *     
  • {@link BackpressureOverflowStrategy#DROP_OLDEST} will drop the oldest items in the buffer in order to make
+     *     room for newly emitted ones. Overflow will not generate an {@code onError}, but each drop will invoke
+     *     {@code onOverflow} to signal the overflow to the producer.
    • 
+     * 

+     *
+     * 

+     * 
+     * 

+     *  
Backpressure:

+     *  
The operator honors backpressure from downstream and consumes the current {@code Flowable} in an unbounded
+     *  manner (i.e., not applying backpressure to it).

+     *  
Scheduler:

+     *  
{@code onBackpressureBuffer} does not operate by default on a particular {@link Scheduler}.

+     * 

+     *
+     * @param capacity number of slots available in the buffer.
+     * @param onOverflow action to execute if an item needs to be buffered, but there are no available slots, {@code null} is allowed.
+     * @param overflowStrategy how should the resulting {@code Flowable} react to buffer overflows, {@code null} is not allowed.
+     * @param onDropped the {@link Consumer} to be called with the item that could not be buffered due to capacity constraints.
+     * @return the new {@code Flowable} instance
+     * @throws NullPointerException if {@code onOverflow}, {@code overflowStrategy} or {@code onDropped} is {@code null}
+     * @throws IllegalArgumentException if {@code capacity} is non-positive
+     * @see ReactiveX operators documentation: backpressure operators
+     * @since 3.1.7
+     */
+    @CheckReturnValue
+    @NonNull
+    @BackpressureSupport(BackpressureKind.SPECIAL)
+    @SchedulerSupport(SchedulerSupport.NONE)
+    @Experimental
+    public final Flowable onBackpressureBuffer(long capacity, @Nullable Action onOverflow, @NonNull BackpressureOverflowStrategy overflowStrategy, @NonNull Consumer onDropped) {
+        Objects.requireNonNull(overflowStrategy, "overflowStrategy is null");
+        Objects.requireNonNull(onDropped, "onDropped is null");
+        ObjectHelper.verifyPositive(capacity, "capacity");
+        return RxJavaPlugins.onAssembly(new FlowableOnBackpressureBufferStrategy<>(this, capacity, onOverflow, overflowStrategy, onDropped));
+    }
     /**
      * Drops items from the current {@code Flowable} if the downstream is not ready to receive new items (indicated
      * by a lack of {@link Subscription#request(long)} calls from it).
@@ -12703,7 +12852,46 @@ public final Flowable onBackpressureDrop(@NonNull Consumer onDrop)
     @SchedulerSupport(SchedulerSupport.NONE)
     @NonNull
     public final Flowable onBackpressureLatest() {
-        return RxJavaPlugins.onAssembly(new FlowableOnBackpressureLatest<>(this));
+        return RxJavaPlugins.onAssembly(new FlowableOnBackpressureLatest<>(this, null));
+    }
+
+    /**
+     * Drops all but the latest item emitted by the current {@code Flowable} if the downstream is not ready to receive
+     * new items (indicated by a lack of {@link Subscription#request(long)} calls from it) and emits this latest
+     * item when the downstream becomes ready.
+     * 

+     * 
+     * 

+     * Its behavior is logically equivalent to {@code blockingLatest()} with the exception that
+     * the downstream is not blocking while requesting more values.
+     * 

+     * Note that if the current {@code Flowable} does support backpressure, this operator ignores that capability
+     * and doesn't propagate any backpressure requests from downstream.
+     * 

+     * Note that due to the nature of how backpressure requests are propagated through subscribeOn/observeOn,
+     * requesting more than 1 from downstream doesn't guarantee a continuous delivery of {@code onNext} events.
+     * 

+     *  
Backpressure:

+     *  
The operator honors backpressure from downstream and consumes the current {@code Flowable} in an unbounded
+     *  manner (i.e., not applying backpressure to it).

+     *  
Scheduler:

+     *  
{@code onBackpressureLatest} does not operate by default on a particular {@link Scheduler}.

+     * 

+     *
+     * @param onDropped
+     *        called with the current entry when it has been replaced by a new one
+     * @throws NullPointerException if {@code onDropped} is {@code null}
+     * @return the new {@code Flowable} instance
+     * @since 3.1.7
+     */
+    @CheckReturnValue
+    @BackpressureSupport(BackpressureKind.UNBOUNDED_IN)
+    @SchedulerSupport(SchedulerSupport.NONE)
+    @NonNull
+    @Experimental
+     public final Flowable onBackpressureLatest(@NonNull Consumer onDropped) {
+        Objects.requireNonNull(onDropped, "onDropped is null");
+        return RxJavaPlugins.onAssembly(new FlowableOnBackpressureLatest<>(this, onDropped));
     }
 
     /**
@@ -14672,7 +14860,7 @@ public final Flowable sample(long period, @NonNull TimeUnit unit, boolean emi
     public final Flowable sample(long period, @NonNull TimeUnit unit, @NonNull Scheduler scheduler) {
         Objects.requireNonNull(unit, "unit is null");
         Objects.requireNonNull(scheduler, "scheduler is null");
-        return RxJavaPlugins.onAssembly(new FlowableSampleTimed<>(this, period, unit, scheduler, false));
+        return RxJavaPlugins.onAssembly(new FlowableSampleTimed<>(this, period, unit, scheduler, false, null));
     }
 
     /**
@@ -14713,7 +14901,51 @@ public final Flowable sample(long period, @NonNull TimeUnit unit, @NonNull Sc
     public final Flowable sample(long period, @NonNull TimeUnit unit, @NonNull Scheduler scheduler, boolean emitLast) {
         Objects.requireNonNull(unit, "unit is null");
         Objects.requireNonNull(scheduler, "scheduler is null");
-        return RxJavaPlugins.onAssembly(new FlowableSampleTimed<>(this, period, unit, scheduler, emitLast));
+        return RxJavaPlugins.onAssembly(new FlowableSampleTimed<>(this, period, unit, scheduler, emitLast, null));
+    }
+
+    /**
+     * Returns a {@code Flowable} that emits the most recently emitted item (if any) emitted by the current {@code Flowable}
+     * within periodic time intervals, where the intervals are defined on a particular {@link Scheduler}
+     * and optionally emit the very last upstream item when the upstream completes.
+     * 

+     * 
+     * 

+     *  
Backpressure:

+     *  
This operator does not support backpressure as it uses time to control data flow.

+     *  
Scheduler:

+     *  
You specify which {@code Scheduler} this operator will use.

+     * 

+     *
+     * @param period
+     *            the sampling rate
+     * @param unit
+     *            the {@link TimeUnit} in which {@code period} is defined
+     * @param scheduler
+     *            the {@code Scheduler} to use when sampling
+     * @param emitLast
+     *            if {@code true} and the upstream completes while there is still an unsampled item available,
+     *            that item is emitted to downstream before completion
+     *            if {@code false}, an unsampled last item is ignored.
+     * @param onDropped
+     *            called with the current entry when it has been replaced by a new one
+     * @return the new {@code Flowable} instance
+     * @throws NullPointerException if {@code unit} or {@code scheduler} is {@code null} or {@code onDropped} is {@code null}
+     * @see ReactiveX operators documentation: Sample
+     * @see RxJava wiki: Backpressure
+     * @see #throttleLast(long, TimeUnit, Scheduler)
+     * @since 3.1.6 - Experimental
+     */
+    @CheckReturnValue
+    @NonNull
+    @BackpressureSupport(BackpressureKind.ERROR)
+    @SchedulerSupport(SchedulerSupport.CUSTOM)
+    @Experimental
+    public final Flowable sample(long period, @NonNull TimeUnit unit, @NonNull Scheduler scheduler, boolean emitLast, @NonNull Consumer onDropped) {
+        Objects.requireNonNull(unit, "unit is null");
+        Objects.requireNonNull(scheduler, "scheduler is null");
+        Objects.requireNonNull(onDropped, "onDropped is null");
+        return RxJavaPlugins.onAssembly(new FlowableSampleTimed<>(this, period, unit, scheduler, emitLast, onDropped));
     }
 
     /**
@@ -15816,7 +16048,7 @@ public final Disposable subscribe(@NonNull Consumer onNext, @NonNull
      * terminates or this particular {@code Disposable} is disposed, the {@code Subscriber} is removed
      * from the given container.
      * 

-     * The {@coded Subscriber} will be removed after the callback for the terminal event has been invoked.
+     * The {@code Subscriber} will be removed after the callback for the terminal event has been invoked.
      * 

      *  
Backpressure:

      *  
The operator consumes the current {@code Flowable} in an unbounded manner (i.e., no
@@ -17096,7 +17328,50 @@ public final Flowable throttleFirst(long windowDuration, @NonNull TimeUnit un
     public final Flowable throttleFirst(long skipDuration, @NonNull TimeUnit unit, @NonNull Scheduler scheduler) {
         Objects.requireNonNull(unit, "unit is null");
         Objects.requireNonNull(scheduler, "scheduler is null");
-        return RxJavaPlugins.onAssembly(new FlowableThrottleFirstTimed<>(this, skipDuration, unit, scheduler));
+        return RxJavaPlugins.onAssembly(new FlowableThrottleFirstTimed<>(this, skipDuration, unit, scheduler, null));
+    }
+
+    /**
+     * Returns a {@code Flowable} that emits only the first item emitted by the current {@code Flowable} during sequential
+     * time windows of a specified duration, where the windows are managed by a specified {@link Scheduler}.
+     * 

+     * This differs from {@link #throttleLast} in that this only tracks the passage of time whereas
+     * {@link #throttleLast} ticks at scheduled intervals.
+     * 

+     * 
+     * 

+     *  
Backpressure:

+     *  
This operator does not support backpressure as it uses time to control data flow.

+     *  
Scheduler:

+     *  
You specify which {@code Scheduler} this operator will use.

+     * 

+     *
+     * @param skipDuration
+     *            time to wait before emitting another item after emitting the last item
+     * @param unit
+     *            the unit of time of {@code skipDuration}
+     * @param scheduler
+     *            the {@code Scheduler} to use internally to manage the timers that handle timeout for each
+     *            event
+     * @param onDropped
+     *            called when an item doesn't get delivered to the downstream
+     *
+     * @return the new {@code Flowable} instance
+     * @throws NullPointerException if {@code unit} or {@code scheduler} or {@code onDropped} is {@code null}
+     * @see ReactiveX operators documentation: Sample
+     * @see RxJava wiki: Backpressure
+     * @since 3.1.6 - Experimental
+     */
+    @CheckReturnValue
+    @NonNull
+    @BackpressureSupport(BackpressureKind.ERROR)
+    @SchedulerSupport(SchedulerSupport.CUSTOM)
+    @Experimental
+    public final Flowable throttleFirst(long skipDuration, @NonNull TimeUnit unit, @NonNull Scheduler scheduler, @NonNull Consumer onDropped) {
+        Objects.requireNonNull(unit, "unit is null");
+        Objects.requireNonNull(scheduler, "scheduler is null");
+        Objects.requireNonNull(onDropped, "onDropped is null");
+        return RxJavaPlugins.onAssembly(new FlowableThrottleFirstTimed<>(this, skipDuration, unit, scheduler, onDropped));
     }
 
     /**
@@ -17170,6 +17445,47 @@ public final Flowable throttleLast(long intervalDuration, @NonNull TimeUnit u
         return sample(intervalDuration, unit, scheduler);
     }
 
+    /**
+     * Returns a {@code Flowable} that emits only the last item emitted by the current {@code Flowable} during sequential
+     * time windows of a specified duration, where the duration is governed by a specified {@link Scheduler}.
+     * 

+     * This differs from {@link #throttleFirst(long, TimeUnit, Scheduler)} in that this ticks along at a scheduled interval whereas
+     * {@code throttleFirst} does not tick, it just tracks the passage of time.
+     * 

+     * 
+     * 

+     *  
Backpressure:

+     *  
This operator does not support backpressure as it uses time to control data flow.

+     *  
Scheduler:

+     *  
You specify which {@code Scheduler} this operator will use.

+     * 

+     *
+     * @param intervalDuration
+     *            duration of windows within which the last item emitted by the current {@code Flowable} will be
+     *            emitted
+     * @param unit
+     *            the unit of time of {@code intervalDuration}
+     * @param scheduler
+     *            the {@code Scheduler} to use internally to manage the timers that handle timeout for each
+     *            event
+     * @param onDropped
+     *          called with the current entry when it has been replaced by a new one
+     * @return the new {@code Flowable} instance
+     * @throws NullPointerException if {@code unit} or {@code scheduler} is {@code null} or {@code onDropped} is {@code null}
+     * @see ReactiveX operators documentation: Sample
+     * @see RxJava wiki: Backpressure
+     * @see #sample(long, TimeUnit, Scheduler)
+     * @since 3.1.6 - Experimental
+     */
+    @CheckReturnValue
+    @BackpressureSupport(BackpressureKind.ERROR)
+    @SchedulerSupport(SchedulerSupport.CUSTOM)
+    @NonNull
+    @Experimental
+    public final Flowable throttleLast(long intervalDuration, @NonNull TimeUnit unit, @NonNull Scheduler scheduler, @NonNull Consumer onDropped) {
+        return sample(intervalDuration, unit, scheduler, false, onDropped);
+    }
+
     /**
      * Throttles items from the upstream {@code Flowable} by first emitting the next
      * item from upstream, then periodically emitting the latest item (if any) when
@@ -17327,7 +17643,61 @@ public final Flowable throttleLatest(long timeout, @NonNull TimeUnit unit, @N
     public final Flowable throttleLatest(long timeout, @NonNull TimeUnit unit, @NonNull Scheduler scheduler, boolean emitLast) {
         Objects.requireNonNull(unit, "unit is null");
         Objects.requireNonNull(scheduler, "scheduler is null");
-        return RxJavaPlugins.onAssembly(new FlowableThrottleLatest<>(this, timeout, unit, scheduler, emitLast));
+        return RxJavaPlugins.onAssembly(new FlowableThrottleLatest<>(this, timeout, unit, scheduler, emitLast, null));
+    }
+
+    /**
+     * Throttles items from the upstream {@code Flowable} by first emitting the next
+     * item from upstream, then periodically emitting the latest item (if any) when
+     * the specified timeout elapses between them, invoking the consumer for any dropped item.
+     * 

+     * 
+     * 

+     * If no items were emitted from the upstream during this timeout phase, the next
+     * upstream item is emitted immediately and the timeout window starts from then.
+     * 

+     *  
Backpressure:

+     *  
This operator does not support backpressure as it uses time to control data flow.
+     *  If the downstream is not ready to receive items, a
+     *  {@link io.reactivex.rxjava3.exceptions.MissingBackpressureException MissingBackpressureException}
+     *  will be signaled.

+     *  
Scheduler:

+     *  
You specify which {@link Scheduler} this operator will use.

+     *  
Error handling:

+     *  

+     *  If the upstream signals an {@code onError} or {@code onDropped} callback crashes,
+     *  the error is delivered immediately to the downstream. If both happen, a {@link CompositeException}
+     *  is created, containing both the upstream and the callback error.
+     *  If the {@code onDropped} callback crashes during cancellation, the exception is forwarded
+     *  to the global error handler via {@link RxJavaPlugins#onError(Throwable)}.
+     *  

+     * 

+     * @param timeout the time to wait after an item emission towards the downstream
+     *                before trying to emit the latest item from upstream again
+     * @param unit    the time unit
+     * @param scheduler the {@code Scheduler} where the timed wait and latest item
+     *                  emission will be performed
+     * @param emitLast If {@code true}, the very last item from the upstream will be emitted
+     *                 immediately when the upstream completes, regardless if there is
+     *                 a timeout window active or not. If {@code false}, the very last
+     *                 upstream item is ignored and the flow terminates.
+     * @param onDropped called when an item is replaced by a newer item that doesn't get delivered
+     *                 to the downstream, including the very last item if {@code emitLast} is {@code false}
+     *                 and the current undelivered item when the sequence gets canceled.
+     * @return the new {@code Flowable} instance
+     * @throws NullPointerException if {@code unit}, {@code scheduler} or {@code onDropped} is {@code null}
+     * @since 3.1.6 - Experimental
+     */
+    @CheckReturnValue
+    @NonNull
+    @BackpressureSupport(BackpressureKind.ERROR)
+    @SchedulerSupport(SchedulerSupport.CUSTOM)
+    @Experimental
+    public final Flowable throttleLatest(long timeout, @NonNull TimeUnit unit, @NonNull Scheduler scheduler, boolean emitLast, @NonNull Consumer onDropped) {
+        Objects.requireNonNull(unit, "unit is null");
+        Objects.requireNonNull(scheduler, "scheduler is null");
+        Objects.requireNonNull(onDropped, "onDropped is null");
+        return RxJavaPlugins.onAssembly(new FlowableThrottleLatest<>(this, timeout, unit, scheduler, emitLast, onDropped));
     }
 
     /**
@@ -17405,6 +17775,49 @@ public final Flowable throttleWithTimeout(long timeout, @NonNull TimeUnit uni
         return debounce(timeout, unit, scheduler);
     }
 
+    /**
+     * Returns a {@code Flowable} that mirrors the current {@code Flowable}, except that it drops items emitted by the
+     * current {@code Flowable} that are followed by newer items before a timeout value expires on a specified
+     * {@link Scheduler}. The timer resets on each emission (alias to {@link #debounce(long, TimeUnit, Scheduler, Consumer)}).
+     * 

+     * Note: If items keep being emitted by the current {@code Flowable} faster than the timeout then no items
+     * will be emitted by the resulting {@code Flowable}.
+     * 

+     * 
+     * 

+     *  
Backpressure:

+     *  
This operator does not support backpressure as it uses time to control data flow.

+     *  
Scheduler:

+     *  
You specify which {@code Scheduler} this operator will use.

+     * 

+     *
+     * @param timeout
+     *            the length of the window of time that must pass after the emission of an item from the current
+     *            {@code Flowable} in which it emits no items in order for the item to be emitted by the
+     *            resulting {@code Flowable}
+     * @param unit
+     *            the unit of time for the specified {@code timeout}
+     * @param scheduler
+     *            the {@code Scheduler} to use internally to manage the timers that handle the timeout for each
+     *            item
+     * @param onDropped
+     *            called with the current entry when it has been replaced by a new one
+     * @return the new {@code Flowable} instance
+     * @throws NullPointerException if {@code unit} or {@code scheduler} is {@code null} or {@code onDropped} is {@code null}
+     * @see ReactiveX operators documentation: Debounce
+     * @see RxJava wiki: Backpressure
+     * @see #debounce(long, TimeUnit, Scheduler, Consumer)
+     * @since 3.1.6 - Experimental
+     */
+    @CheckReturnValue
+    @BackpressureSupport(BackpressureKind.ERROR)
+    @SchedulerSupport(SchedulerSupport.CUSTOM)
+    @NonNull
+    @Experimental
+    public final Flowable throttleWithTimeout(long timeout, @NonNull TimeUnit unit, @NonNull Scheduler scheduler, @NonNull Consumer onDropped) {
+        return debounce(timeout, unit, scheduler, onDropped);
+    }
+
     /**
      * Returns a {@code Flowable} that emits records of the time interval between consecutive items emitted by the
      * current {@code Flowable}.
@@ -19851,7 +20264,7 @@ public final TestSubscriber test(long initialRequest, boolean cancel) { // No
      * 
      * 

      * Note that the operator takes an already instantiated, running or terminated {@code CompletionStage}.
-     * If the optional is to be created per consumer upon subscription, use {@link #defer(Supplier)}
+     * If the {@code CompletionStage} is to be created per consumer upon subscription, use {@link #defer(Supplier)}
      * around {@code fromCompletionStage}:
      * 

      * Flowable.defer(() -> Flowable.fromCompletionStage(createCompletionStage()));
@@ -19986,7 +20399,7 @@ public final TestSubscriber test(long initialRequest, boolean cancel) { // No
     @BackpressureSupport(BackpressureKind.UNBOUNDED_IN)
     @SchedulerSupport(SchedulerSupport.NONE)
     @NonNull
-    public final <@NonNull R, @NonNull A> Single collect(@NonNull Collector collector) {
+    public final <@NonNull R, @Nullable A> Single collect(@NonNull Collector collector) {
         Objects.requireNonNull(collector, "collector is null");
         return RxJavaPlugins.onAssembly(new FlowableCollectWithCollectorSingle<>(this, collector));
     }
diff --git a/src/main/java/io/reactivex/rxjava3/core/Maybe.java b/src/main/java/io/reactivex/rxjava3/core/Maybe.java
index bbb3a10d4b2..8ae4137c839 100644
--- a/src/main/java/io/reactivex/rxjava3/core/Maybe.java
+++ b/src/main/java/io/reactivex/rxjava3/core/Maybe.java
@@ -110,7 +110,7 @@
  * @since 2.0
  * @see io.reactivex.rxjava3.observers.DisposableMaybeObserver
  */
-public abstract class Maybe implements MaybeSource {
+public abstract class Maybe<@NonNull T> implements MaybeSource {
 
     /**
      * Runs multiple {@link MaybeSource}s provided by an {@link Iterable} sequence and
@@ -889,7 +889,7 @@ public abstract class Maybe implements MaybeSource {
     @CheckReturnValue
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
-    public static <@NonNull T> Maybe defer(@NonNull Supplier> supplier) {
+    public static <@NonNull T> Maybe defer(@NonNull Supplier> supplier) {
         Objects.requireNonNull(supplier, "supplier is null");
         return RxJavaPlugins.onAssembly(new MaybeDefer<>(supplier));
     }
@@ -961,7 +961,7 @@ public abstract class Maybe implements MaybeSource {
     @CheckReturnValue
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
-    public static <@NonNull T> Maybe error(@NonNull Supplier supplier) {
+    public static <@NonNull T> Maybe error(@NonNull Supplier supplier) {
         Objects.requireNonNull(supplier, "supplier is null");
         return RxJavaPlugins.onAssembly(new MaybeErrorCallable<>(supplier));
     }
@@ -1079,7 +1079,7 @@ public abstract class Maybe implements MaybeSource {
     @CheckReturnValue
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
-    public static <@NonNull T> Maybe fromCallable(@NonNull Callable callable) {
+    public static  Maybe<@NonNull T> fromCallable(@NonNull Callable callable) {
         Objects.requireNonNull(callable, "callable is null");
         return RxJavaPlugins.onAssembly(new MaybeFromCallable<>(callable));
     }
@@ -1109,6 +1109,7 @@ public abstract class Maybe implements MaybeSource {
      * @return the new {@code Maybe} instance
      * @throws NullPointerException if {@code future} is {@code null}
      * @see ReactiveX operators documentation: From
+     * @see #fromCompletionStage(CompletionStage)
      */
     @CheckReturnValue
     @NonNull
@@ -1147,6 +1148,7 @@ public abstract class Maybe implements MaybeSource {
      * @return the new {@code Maybe} instance
      * @throws NullPointerException if {@code future} or {@code unit} is {@code null}
      * @see ReactiveX operators documentation: From
+     * @see #fromCompletionStage(CompletionStage)
      */
     @CheckReturnValue
     @NonNull
@@ -1285,7 +1287,7 @@ public abstract class Maybe implements MaybeSource {
     @CheckReturnValue
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
-    public static <@NonNull T> Maybe fromSupplier(@NonNull Supplier supplier) {
+    public static  Maybe<@NonNull T> fromSupplier(@NonNull Supplier supplier) {
         Objects.requireNonNull(supplier, "supplier is null");
         return RxJavaPlugins.onAssembly(new MaybeFromSupplier<>(supplier));
     }
@@ -6145,7 +6147,7 @@ public final TestObserver test(boolean dispose) {
      * 
      * 

      * Note that the operator takes an already instantiated, running or terminated {@code CompletionStage}.
-     * If the optional is to be created per consumer upon subscription, use {@link #defer(Supplier)}
+     * If the {@code CompletionStage} is to be created per consumer upon subscription, use {@link #defer(Supplier)}
      * around {@code fromCompletionStage}:
      * 

      * Maybe.defer(() -> Maybe.fromCompletionStage(createCompletionStage()));
diff --git a/src/main/java/io/reactivex/rxjava3/core/Observable.java b/src/main/java/io/reactivex/rxjava3/core/Observable.java
index 2206319b18d..fcf809cdf6b 100644
--- a/src/main/java/io/reactivex/rxjava3/core/Observable.java
+++ b/src/main/java/io/reactivex/rxjava3/core/Observable.java
@@ -1790,7 +1790,7 @@ public static int bufferSize() {
     @CheckReturnValue
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
-    public static <@NonNull T> Observable defer(@NonNull Supplier> supplier) {
+    public static <@NonNull T> Observable defer(@NonNull Supplier> supplier) {
         Objects.requireNonNull(supplier, "supplier is null");
         return RxJavaPlugins.onAssembly(new ObservableDefer<>(supplier));
     }
@@ -1839,7 +1839,7 @@ public static int bufferSize() {
     @CheckReturnValue
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
-    public static <@NonNull T> Observable error(@NonNull Supplier supplier) {
+    public static <@NonNull T> Observable error(@NonNull Supplier supplier) {
         Objects.requireNonNull(supplier, "supplier is null");
         return RxJavaPlugins.onAssembly(new ObservableError<>(supplier));
     }
@@ -2020,6 +2020,7 @@ public static int bufferSize() {
      * @return the new {@code Observable} instance
      * @throws NullPointerException if {@code future} is {@code null}
      * @see ReactiveX operators documentation: From
+     * @see #fromCompletionStage(CompletionStage)
      */
     @CheckReturnValue
     @NonNull
@@ -2062,6 +2063,7 @@ public static int bufferSize() {
      * @return the new {@code Observable} instance
      * @throws NullPointerException if {@code future} or {@code unit} is {@code null}
      * @see ReactiveX operators documentation: From
+     * @see #fromCompletionStage(CompletionStage)
      */
     @CheckReturnValue
     @NonNull
@@ -5520,7 +5522,6 @@ public final T blockingFirst(@NonNull T defaultItem) {
      * @see #blockingForEach(Consumer, int)
      */
     @SchedulerSupport(SchedulerSupport.NONE)
-    @NonNull
     public final void blockingForEach(@NonNull Consumer onNext) {
         blockingForEach(onNext, bufferSize());
     }
@@ -5560,7 +5561,6 @@ public final void blockingForEach(@NonNull Consumer onNext) {
      * @see #subscribe(Consumer)
      */
     @SchedulerSupport(SchedulerSupport.NONE)
-    @NonNull
     public final void blockingForEach(@NonNull Consumer onNext, int capacityHint) {
         Objects.requireNonNull(onNext, "onNext is null");
         Iterator it = blockingIterable(capacityHint).iterator();
@@ -6668,8 +6668,10 @@ public final Observable cacheWithInitialCapacity(int initialCapacity) {
     }
 
     /**
-     * Returns an {@code Observable} that emits the items emitted by the current {@code Observable}, converted to the specified
-     * type.
+     * Returns an {@code Observable} that emits the upstream items while
+     * they can be cast via {@link Class#cast(Object)} until the upstream terminates,
+     * or until the upstream signals an item which can't be cast,
+     * resulting in a {@link ClassCastException} to be signaled to the downstream.
      * 

      * 
      * 

@@ -6679,8 +6681,7 @@ public final Observable cacheWithInitialCapacity(int initialCapacity) {
      *
      * @param  the output value type cast to
      * @param clazz
-     *            the target class type that {@code cast} will cast the items emitted by the current {@code Observable}
-     *            into before emitting them from the resulting {@code Observable}
+     *            the target class to use to try and cast the upstream items into
      * @return the new {@code Observable} instance
      * @throws NullPointerException if {@code clazz} is {@code null}
      * @see ReactiveX operators documentation: Map
@@ -7328,7 +7329,7 @@ public final Completable concatMapCompletableDelayError(@NonNull Function
-     * 
+     * 
      * 

      *  
Scheduler:

      *  
{@code concatMapMaybe} does not operate by default on a particular {@link Scheduler}.

@@ -7356,7 +7357,7 @@ public final Completable concatMapCompletableDelayError(@NonNull Function
-     * 
+     * 
      * 

      *  
Scheduler:

      *  
{@code concatMapMaybe} does not operate by default on a particular {@link Scheduler}.

@@ -7389,7 +7390,7 @@ public final Completable concatMapCompletableDelayError(@NonNull Function
-     * 
+     * 
      * 

      *  
Scheduler:

      *  
{@code concatMapMaybeDelayError} does not operate by default on a particular {@link Scheduler}.

@@ -7417,7 +7418,7 @@ public final Completable concatMapCompletableDelayError(@NonNull Function
-     * 
+     * 
      * 

      *  
Scheduler:

      *  
{@code concatMapMaybeDelayError} does not operate by default on a particular {@link Scheduler}.

@@ -7451,7 +7452,7 @@ public final Completable concatMapCompletableDelayError(@NonNull Function
-     * 
+     * 
      * 

      *  
Scheduler:

      *  
{@code concatMapMaybeDelayError} does not operate by default on a particular {@link Scheduler}.

@@ -7489,7 +7490,7 @@ public final Completable concatMapCompletableDelayError(@NonNull Function
-     * 
+     * 
      * 

      *  
Scheduler:

      *  
{@code concatMapSingle} does not operate by default on a particular {@link Scheduler}.

@@ -7517,7 +7518,7 @@ public final Completable concatMapCompletableDelayError(@NonNull Function
-     * 
+     * 
      * 

      *  
Scheduler:

      *  
{@code concatMapSingle} does not operate by default on a particular {@link Scheduler}.

@@ -7550,7 +7551,7 @@ public final Completable concatMapCompletableDelayError(@NonNull Function
-     * 
+     * 
      * 

      *  
Scheduler:

      *  
{@code concatMapSingleDelayError} does not operate by default on a particular {@link Scheduler}.

@@ -7578,7 +7579,7 @@ public final Completable concatMapCompletableDelayError(@NonNull Function
-     * 
+     * 
      * 

      *  
Scheduler:

      *  
{@code concatMapSingleDelayError} does not operate by default on a particular {@link Scheduler}.

@@ -7612,7 +7613,7 @@ public final Completable concatMapCompletableDelayError(@NonNull Function
-     * 
+     * 
      * 

      *  
Scheduler:

      *  
{@code concatMapSingleDelayError} does not operate by default on a particular {@link Scheduler}.

@@ -7896,7 +7897,55 @@ public final Observable debounce(long timeout, @NonNull TimeUnit unit) {
     public final Observable debounce(long timeout, @NonNull TimeUnit unit, @NonNull Scheduler scheduler) {
         Objects.requireNonNull(unit, "unit is null");
         Objects.requireNonNull(scheduler, "scheduler is null");
-        return RxJavaPlugins.onAssembly(new ObservableDebounceTimed<>(this, timeout, unit, scheduler));
+        return RxJavaPlugins.onAssembly(new ObservableDebounceTimed<>(this, timeout, unit, scheduler, null));
+    }
+
+    /**
+     * Returns an {@code Observable} that mirrors the current {@code Observable}, except that it drops items emitted by the
+     * current {@code Observable} that are followed by newer items before a timeout value expires on a specified
+     * {@link Scheduler}. The timer resets on each emission.
+     * 

+     * Note: If items keep being emitted by the current {@code Observable} faster than the timeout then no items
+     * will be emitted by the resulting {@code Observable}.
+     * 

+     * 
+     * 

+     * Delivery of the item after the grace period happens on the given {@code Scheduler}'s
+     * {@code Worker} which if takes too long, a newer item may arrive from the upstream, causing the
+     * {@code Worker}'s task to get disposed, which may also interrupt any downstream blocking operation
+     * (yielding an {@code InterruptedException}). It is recommended processing items
+     * that may take long time to be moved to another thread via {@link #observeOn} applied after
+     * {@code debounce} itself.
+     * 

+     *  
Scheduler:

+     *  
You specify which {@code Scheduler} this operator will use.

+     * 

+     *
+     * @param timeout
+     *            the time each item has to be "the most recent" of those emitted by the current {@code Observable} to
+     *            ensure that it's not dropped
+     * @param unit
+     *            the unit of time for the specified {@code timeout}
+     * @param scheduler
+     *            the {@code Scheduler} to use internally to manage the timers that handle the timeout for each
+     *            item
+     * @param onDropped
+     *          called with the current entry when it has been replaced by a new one
+     * @return the new {@code Observable} instance
+     * @throws NullPointerException if {@code unit} or {@code scheduler} is {@code null} } or {@code onDropped} is {@code null}
+     * @see ReactiveX operators documentation: Debounce
+     * @see #throttleWithTimeout(long, TimeUnit, Scheduler, Consumer)
+     * @since 3.1.6 - Experimental
+     */
+    @CheckReturnValue
+    @SchedulerSupport(SchedulerSupport.CUSTOM)
+    @NonNull
+    @Experimental
+    public final Observable debounce(long timeout, @NonNull TimeUnit unit, @NonNull Scheduler scheduler, @NonNull Consumer onDropped) {
+        Objects.requireNonNull(unit, "unit is null");
+        Objects.requireNonNull(scheduler, "scheduler is null");
+        Objects.requireNonNull(onDropped, "onDropped is null");
+        return RxJavaPlugins.onAssembly(new ObservableDebounceTimed<>(this, timeout, unit, scheduler, onDropped));
     }
 
     /**
@@ -8953,7 +9002,7 @@ public final Maybe firstElement() {
      * Returns a {@link Single} that emits only the very first item emitted by the current {@code Observable}, or a default item
      * if the current {@code Observable} completes without emitting any items.
      * 

-     * 
+     * 
      * 

      *  
Scheduler:

      *  
{@code first} does not operate by default on a particular {@link Scheduler}.

@@ -12036,7 +12085,6 @@ public final Observable retryWhen(
      * @throws NullPointerException if {@code observer} is {@code null}
      */
     @SchedulerSupport(SchedulerSupport.NONE)
-    @NonNull
     public final void safeSubscribe(@NonNull Observer observer) {
         Objects.requireNonNull(observer, "observer is null");
         if (observer instanceof SafeObserver) {
@@ -12131,7 +12179,7 @@ public final Observable sample(long period, @NonNull TimeUnit unit, boolean e
     public final Observable sample(long period, @NonNull TimeUnit unit, @NonNull Scheduler scheduler) {
         Objects.requireNonNull(unit, "unit is null");
         Objects.requireNonNull(scheduler, "scheduler is null");
-        return RxJavaPlugins.onAssembly(new ObservableSampleTimed<>(this, period, unit, scheduler, false));
+        return RxJavaPlugins.onAssembly(new ObservableSampleTimed<>(this, period, unit, scheduler, false, null));
     }
 
     /**
@@ -12168,7 +12216,46 @@ public final Observable sample(long period, @NonNull TimeUnit unit, @NonNull
     public final Observable sample(long period, @NonNull TimeUnit unit, @NonNull Scheduler scheduler, boolean emitLast) {
         Objects.requireNonNull(unit, "unit is null");
         Objects.requireNonNull(scheduler, "scheduler is null");
-        return RxJavaPlugins.onAssembly(new ObservableSampleTimed<>(this, period, unit, scheduler, emitLast));
+        return RxJavaPlugins.onAssembly(new ObservableSampleTimed<>(this, period, unit, scheduler, emitLast, null));
+    }
+
+    /**
+     * Returns an {@code Observable} that emits the most recently emitted item (if any) emitted by the current {@code Observable}
+     * within periodic time intervals, where the intervals are defined on a particular {@link Scheduler}.
+     * 

+     * 
+     * 

+     *  
Scheduler:

+     *  
You specify which {@code Scheduler} this operator will use.

+     * 

+     *
+     * @param period
+     *            the sampling rate
+     * @param unit
+     *            the {@link TimeUnit} in which {@code period} is defined
+     * @param scheduler
+     *            the {@code Scheduler} to use when sampling
+     * @param emitLast
+     *            if {@code true} and the upstream completes while there is still an unsampled item available,
+     *            that item is emitted to downstream before completion
+     *            if {@code false}, an unsampled last item is ignored.
+     * @param onDropped
+     *          called with the current entry when it has been replaced by a new one
+     * @return the new {@code Observable} instance
+     * @throws NullPointerException if {@code unit} or {@code scheduler} is {@code null} or {@code onDropped} is {@code null}
+     * @see ReactiveX operators documentation: Sample
+     * @see #throttleLast(long, TimeUnit, Scheduler)
+     * @since 3.1.6 - Experimental
+     */
+    @CheckReturnValue
+    @SchedulerSupport(SchedulerSupport.CUSTOM)
+    @NonNull
+    @Experimental
+    public final Observable sample(long period, @NonNull TimeUnit unit, @NonNull Scheduler scheduler, boolean emitLast, @NonNull Consumer onDropped) {
+        Objects.requireNonNull(unit, "unit is null");
+        Objects.requireNonNull(scheduler, "scheduler is null");
+        Objects.requireNonNull(onDropped, "onDropped is null");
+        return RxJavaPlugins.onAssembly(new ObservableSampleTimed<>(this, period, unit, scheduler, emitLast, onDropped));
     }
 
     /**
@@ -14166,7 +14253,46 @@ public final Observable throttleFirst(long windowDuration, @NonNull TimeUnit
     public final Observable throttleFirst(long skipDuration, @NonNull TimeUnit unit, @NonNull Scheduler scheduler) {
         Objects.requireNonNull(unit, "unit is null");
         Objects.requireNonNull(scheduler, "scheduler is null");
-        return RxJavaPlugins.onAssembly(new ObservableThrottleFirstTimed<>(this, skipDuration, unit, scheduler));
+        return RxJavaPlugins.onAssembly(new ObservableThrottleFirstTimed<>(this, skipDuration, unit, scheduler, null));
+    }
+
+    /**
+     * Returns an {@code Observable} that emits only the first item emitted by the current {@code Observable} during sequential
+     * time windows of a specified duration, where the windows are managed by a specified {@link Scheduler}.
+     * 

+     * This differs from {@link #throttleLast} in that this only tracks passage of time whereas
+     * {@code throttleLast} ticks at scheduled intervals.
+     * 

+     * 
+     * 

+     *  
Scheduler:

+     *  
You specify which {@code Scheduler} this operator will use.

+     * 

+     *
+     * @param skipDuration
+     *            time to wait before emitting another item after emitting the last item
+     * @param unit
+     *            the unit of time of {@code skipDuration}
+     * @param scheduler
+     *            the {@code Scheduler} to use internally to manage the timers that handle timeout for each
+     *            event
+     * @param onDropped
+     *            called when an item doesn't get delivered to the downstream
+     *
+     * @return the new {@code Observable} instance
+     * @throws NullPointerException if {@code unit} or {@code scheduler} or {@code onDropped} is {@code null}
+     * @see ReactiveX operators documentation: Sample
+     * @since 3.1.6 - Experimental
+     */
+    @CheckReturnValue
+    @SchedulerSupport(SchedulerSupport.CUSTOM)
+    @NonNull
+    @Experimental
+    public final Observable throttleFirst(long skipDuration, @NonNull TimeUnit unit, @NonNull Scheduler scheduler, @NonNull Consumer onDropped) {
+        Objects.requireNonNull(unit, "unit is null");
+        Objects.requireNonNull(scheduler, "scheduler is null");
+        Objects.requireNonNull(onDropped, "onDropped is null");
+        return RxJavaPlugins.onAssembly(new ObservableThrottleFirstTimed<>(this, skipDuration, unit, scheduler, onDropped));
     }
 
     /**
@@ -14199,6 +14325,43 @@ public final Observable throttleLast(long intervalDuration, @NonNull TimeUnit
         return sample(intervalDuration, unit);
     }
 
+    /**
+     * Returns an {@code Observable} that emits only the last item emitted by the current {@code Observable} during sequential
+     * time windows of a specified duration, where the duration is governed by a specified {@link Scheduler}.
+     * 

+     * This differs from {@link #throttleFirst} in that this ticks along at a scheduled interval whereas
+     * {@code throttleFirst} does not tick, it just tracks passage of time.
+     * 

+     * 
+     * 

+     *  
Scheduler:

+     *  
You specify which {@code Scheduler} this operator will use.

+     * 

+     *
+     * @param intervalDuration
+     *            duration of windows within which the last item emitted by the current {@code Observable} will be
+     *            emitted
+     * @param unit
+     *            the unit of time of {@code intervalDuration}
+     * @param scheduler
+     *            the {@code Scheduler} to use internally to manage the timers that handle timeout for each
+     *            event
+     * @param onDropped
+     *          called with the current entry when it has been replaced by a new one
+     * @return the new {@code Observable} instance
+     * @throws NullPointerException if {@code unit} or {@code scheduler} is {@code null} or {@code onDropped} is {@code null}
+     * @see ReactiveX operators documentation: Sample
+     * @see #sample(long, TimeUnit, Scheduler)
+     * @since 3.1.6 - Experimental
+     */
+    @CheckReturnValue
+    @SchedulerSupport(SchedulerSupport.CUSTOM)
+    @NonNull
+    @Experimental
+    public final Observable throttleLast(long intervalDuration, @NonNull TimeUnit unit, @NonNull Scheduler scheduler, @NonNull Consumer onDropped) {
+        return sample(intervalDuration, unit, scheduler, false, onDropped);
+    }
+
     /**
      * Returns an {@code Observable} that emits only the last item emitted by the current {@code Observable} during sequential
      * time windows of a specified duration, where the duration is governed by a specified {@link Scheduler}.
@@ -14365,7 +14528,55 @@ public final Observable throttleLatest(long timeout, @NonNull TimeUnit unit,
     public final Observable throttleLatest(long timeout, @NonNull TimeUnit unit, @NonNull Scheduler scheduler, boolean emitLast) {
         Objects.requireNonNull(unit, "unit is null");
         Objects.requireNonNull(scheduler, "scheduler is null");
-        return RxJavaPlugins.onAssembly(new ObservableThrottleLatest<>(this, timeout, unit, scheduler, emitLast));
+        return RxJavaPlugins.onAssembly(new ObservableThrottleLatest<>(this, timeout, unit, scheduler, emitLast, null));
+    }
+
+    /**
+     * Throttles items from the current {@code Observable} by first emitting the next
+     * item from upstream, then periodically emitting the latest item (if any) when
+     * the specified timeout elapses between them, invoking the consumer for any dropped item.
+     * 

+     * 
+     * 

+     * If no items were emitted from the upstream during this timeout phase, the next
+     * upstream item is emitted immediately and the timeout window starts from then.
+     * 

+     *  
Scheduler:

+     *  
You specify which {@link Scheduler} this operator will use.

+     *  
Error handling:

+     *  

+     *  If the upstream signals an {@code onError} or {@code onDropped} callback crashes,
+     *  the error is delivered immediately to the downstream. If both happen, a {@link CompositeException}
+     *  is created, containing both the upstream and the callback error.
+     *  If the {@code onDropped} callback crashes when the sequence gets disposed, the exception is forwarded
+     *  to the global error handler via {@link RxJavaPlugins#onError(Throwable)}.
+     *  

+     * 

+     * @param timeout the time to wait after an item emission towards the downstream
+     *                before trying to emit the latest item from upstream again
+     * @param unit    the time unit
+     * @param scheduler the {@code Scheduler} where the timed wait and latest item
+     *                  emission will be performed
+     * @param emitLast If {@code true}, the very last item from the upstream will be emitted
+     *                 immediately when the upstream completes, regardless if there is
+     *                 a timeout window active or not. If {@code false}, the very last
+     *                 upstream item is ignored and the flow terminates.
+     * @param onDropped called when an item is replaced by a newer item that doesn't get delivered
+     *                 to the downstream, including the very last item if {@code emitLast} is {@code false}
+     *                 and the current undelivered item when the sequence gets disposed.
+     * @return the new {@code Observable} instance
+     * @throws NullPointerException if {@code unit}, {@code scheduler} or {@code onDropped} is {@code null}
+     * @since 3.1.6 - Experimental
+     */
+    @CheckReturnValue
+    @SchedulerSupport(SchedulerSupport.CUSTOM)
+    @NonNull
+    @Experimental
+    public final Observable throttleLatest(long timeout, @NonNull TimeUnit unit, @NonNull Scheduler scheduler, boolean emitLast, @NonNull Consumer onDropped) {
+        Objects.requireNonNull(unit, "unit is null");
+        Objects.requireNonNull(scheduler, "scheduler is null");
+        Objects.requireNonNull(onDropped, "onDropped is null");
+        return RxJavaPlugins.onAssembly(new ObservableThrottleLatest<>(this, timeout, unit, scheduler, emitLast, onDropped));
     }
 
     /**
@@ -14435,6 +14646,45 @@ public final Observable throttleWithTimeout(long timeout, @NonNull TimeUnit u
         return debounce(timeout, unit, scheduler);
     }
 
+    /**
+     * Returns an {@code Observable} that mirrors the current {@code Observable}, except that it drops items emitted by the
+     * current {@code Observable} that are followed by newer items before a timeout value expires on a specified
+     * {@link Scheduler}. The timer resets on each emission (Alias to {@link #debounce(long, TimeUnit, Scheduler)}).
+     * 

+     * Note: If items keep being emitted by the current {@code Observable} faster than the timeout then no items
+     * will be emitted by the resulting {@code Observable}.
+     * 

+     * 
+     * 

+     *  
Scheduler:

+     *  
You specify which {@code Scheduler} this operator will use.

+     * 

+     *
+     * @param timeout
+     *            the length of the window of time that must pass after the emission of an item from the current
+     *            {@code Observable}, in which the current {@code Observable} emits no items, in order for the item to be emitted by the
+     *            resulting {@code Observable}
+     * @param unit
+     *            the unit of time for the specified {@code timeout}
+     * @param scheduler
+     *            the {@code Scheduler} to use internally to manage the timers that handle the timeout for each
+     *            item
+     * @param onDropped
+     *          called with the current entry when it has been replaced by a new one
+     * @return the new {@code Observable} instance
+     * @throws NullPointerException if {@code unit} or {@code scheduler} is {@code null} or {@code onDropped} is {@code null}
+     * @see ReactiveX operators documentation: Debounce
+     * @see #debounce(long, TimeUnit, Scheduler, Consumer)
+     * @since 3.1.6 - Experimental
+     */
+    @CheckReturnValue
+    @SchedulerSupport(SchedulerSupport.CUSTOM)
+    @NonNull
+    @Experimental
+    public final Observable throttleWithTimeout(long timeout, @NonNull TimeUnit unit, @NonNull Scheduler scheduler, @NonNull Consumer onDropped) {
+        return debounce(timeout, unit, scheduler, onDropped);
+    }
+
     /**
      * Returns an {@code Observable} that emits records of the time interval between consecutive items emitted by the
      * current {@code Observable}.
@@ -16616,7 +16866,7 @@ public final TestObserver test(boolean dispose) { // NoPMD
      * 
      * 

      * Note that the operator takes an already instantiated, running or terminated {@code CompletionStage}.
-     * If the optional is to be created per consumer upon subscription, use {@link #defer(Supplier)}
+     * If the {@code CompletionStage} is to be created per consumer upon subscription, use {@link #defer(Supplier)}
      * around {@code fromCompletionStage}:
      * 

      * Observable.defer(() -> Observable.fromCompletionStage(createCompletionStage()));
@@ -16736,7 +16986,7 @@ public final TestObserver test(boolean dispose) { // NoPMD
     @CheckReturnValue
     @SchedulerSupport(SchedulerSupport.NONE)
     @NonNull
-    public final <@NonNull R, @NonNull A> Single collect(@NonNull Collector collector) {
+    public final <@NonNull R, @Nullable A> Single collect(@NonNull Collector collector) {
         Objects.requireNonNull(collector, "collector is null");
         return RxJavaPlugins.onAssembly(new ObservableCollectWithCollectorSingle<>(this, collector));
     }
diff --git a/src/main/java/io/reactivex/rxjava3/core/Scheduler.java b/src/main/java/io/reactivex/rxjava3/core/Scheduler.java
index 580e2739cb0..3aa001127ad 100644
--- a/src/main/java/io/reactivex/rxjava3/core/Scheduler.java
+++ b/src/main/java/io/reactivex/rxjava3/core/Scheduler.java
@@ -350,7 +350,7 @@ public Disposable schedulePeriodicallyDirect(@NonNull Runnable run, long initial
      * });
      * 

      *
-     * Slowing down the rate to no more than than 1 a second. This suffers from
+     * Slowing down the rate to no more than 1 a second. This suffers from
      * the same problem as the one above I could find an {@link Flowable}
      * operator that limits the rate without dropping the values (aka leaky
      * bucket algorithm).
diff --git a/src/main/java/io/reactivex/rxjava3/core/Single.java b/src/main/java/io/reactivex/rxjava3/core/Single.java
index ea6a610febe..6cf5a3f7890 100644
--- a/src/main/java/io/reactivex/rxjava3/core/Single.java
+++ b/src/main/java/io/reactivex/rxjava3/core/Single.java
@@ -895,7 +895,7 @@ public abstract class Single<@NonNull T> implements SingleSource {
     @CheckReturnValue
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
-    public static <@NonNull T> Single defer(@NonNull Supplier> supplier) {
+    public static <@NonNull T> Single defer(@NonNull Supplier> supplier) {
         Objects.requireNonNull(supplier, "supplier is null");
         return RxJavaPlugins.onAssembly(new SingleDefer<>(supplier));
     }
@@ -917,7 +917,7 @@ public abstract class Single<@NonNull T> implements SingleSource {
     @CheckReturnValue
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
-    public static <@NonNull T> Single error(@NonNull Supplier supplier) {
+    public static <@NonNull T> Single error(@NonNull Supplier supplier) {
         Objects.requireNonNull(supplier, "supplier is null");
         return RxJavaPlugins.onAssembly(new SingleError<>(supplier));
     }
@@ -5598,7 +5598,7 @@ private static  Single toSingle(@NonNull Flowable source) {
      * 
      * 

      * Note that the operator takes an already instantiated, running or terminated {@code CompletionStage}.
-     * If the optional is to be created per consumer upon subscription, use {@link #defer(Supplier)}
+     * If the {@code CompletionStage} is to be created per consumer upon subscription, use {@link #defer(Supplier)}
      * around {@code fromCompletionStage}:
      * 

      * Single.defer(() -> Single.fromCompletionStage(createCompletionStage()));
diff --git a/src/main/java/io/reactivex/rxjava3/disposables/Disposable.java b/src/main/java/io/reactivex/rxjava3/disposables/Disposable.java
index 67fd2350868..845d603171c 100644
--- a/src/main/java/io/reactivex/rxjava3/disposables/Disposable.java
+++ b/src/main/java/io/reactivex/rxjava3/disposables/Disposable.java
@@ -40,8 +40,8 @@ public interface Disposable {
     /**
      * Construct a {@code Disposable} by wrapping a {@link Runnable} that is
      * executed exactly once when the {@code Disposable} is disposed.
-     * @param run the Runnable to wrap
-     * @return the new Disposable instance
+     * @param run the {@code Runnable} to wrap
+     * @return the new {@code Disposable} instance
      * @throws NullPointerException if {@code run} is {@code null}
      * @since 3.0.0
      */
@@ -54,8 +54,8 @@ static Disposable fromRunnable(@NonNull Runnable run) {
     /**
      * Construct a {@code Disposable} by wrapping a {@link Action} that is
      * executed exactly once when the {@code Disposable} is disposed.
-     * @param action the Action to wrap
-     * @return the new Disposable instance
+     * @param action the {@code Action} to wrap
+     * @return the new {@code Disposable} instance
      * @throws NullPointerException if {@code action} is {@code null}
      * @since 3.0.0
      */
@@ -70,8 +70,8 @@ static Disposable fromAction(@NonNull Action action) {
      * cancelled exactly once when the {@code Disposable} is disposed.
      * 

      * The {@code Future} is cancelled with {@code mayInterruptIfRunning == true}.
-     * @param future the Future to wrap
-     * @return the new Disposable instance
+     * @param future the {@code Future} to wrap
+     * @return the new {@code Disposable} instance
      * @throws NullPointerException if {@code future} is {@code null}
      * @see #fromFuture(Future, boolean)
      * @since 3.0.0
@@ -85,9 +85,9 @@ static Disposable fromFuture(@NonNull Future future) {
     /**
      * Construct a {@code Disposable} by wrapping a {@link Future} that is
      * cancelled exactly once when the {@code Disposable} is disposed.
-     * @param future the Future to wrap
+     * @param future the {@code Future} to wrap
      * @param allowInterrupt if true, the future cancel happens via {@code Future.cancel(true)}
-     * @return the new Disposable instance
+     * @return the new {@code Disposable} instance
      * @throws NullPointerException if {@code future} is {@code null}
      * @since 3.0.0
      */
@@ -100,8 +100,8 @@ static Disposable fromFuture(@NonNull Future future, boolean allowInterrupt)
     /**
      * Construct a {@code Disposable} by wrapping a {@link Subscription} that is
      * cancelled exactly once when the {@code Disposable} is disposed.
-     * @param subscription the Runnable to wrap
-     * @return the new Disposable instance
+     * @param subscription the {@code Runnable} to wrap
+     * @return the new {@code Disposable} instance
      * @throws NullPointerException if {@code subscription} is {@code null}
      * @since 3.0.0
      */
@@ -114,8 +114,8 @@ static Disposable fromSubscription(@NonNull Subscription subscription) {
     /**
      * Construct a {@code Disposable} by wrapping an {@link AutoCloseable} that is
      * closed exactly once when the {@code Disposable} is disposed.
-     * @param autoCloseable the AutoCloseable to wrap
-     * @return the new Disposable instance
+     * @param autoCloseable the {@code AutoCloseable} to wrap
+     * @return the new {@code Disposable} instance
      * @throws NullPointerException if {@code autoCloseable} is {@code null}
      * @since 3.0.0
      */
@@ -128,8 +128,8 @@ static Disposable fromAutoCloseable(@NonNull AutoCloseable autoCloseable) {
     /**
      * Construct an {@link AutoCloseable} by wrapping a {@code Disposable} that is
      * disposed when the returned {@code AutoCloseable} is closed.
-     * @param disposable the Disposable instance
-     * @return the new AutoCloseable instance
+     * @param disposable the {@code Disposable} instance
+     * @return the new {@code AutoCloseable} instance
      * @throws NullPointerException if {@code disposable} is {@code null}
      * @since 3.0.0
      */
diff --git a/src/main/java/io/reactivex/rxjava3/exceptions/MissingBackpressureException.java b/src/main/java/io/reactivex/rxjava3/exceptions/MissingBackpressureException.java
index a817e6fb938..f0a173ba590 100644
--- a/src/main/java/io/reactivex/rxjava3/exceptions/MissingBackpressureException.java
+++ b/src/main/java/io/reactivex/rxjava3/exceptions/MissingBackpressureException.java
@@ -20,6 +20,15 @@ public final class MissingBackpressureException extends RuntimeException {
 
     private static final long serialVersionUID = 8517344746016032542L;
 
+    /**
+     * The default error message.
+     * 

+     * This can happen if the downstream doesn't call {@link org.reactivestreams.Subscription#request(long)}
+     * in time or at all.
+     * @since 3.1.6
+     */
+    public static final String DEFAULT_MESSAGE = "Could not emit value due to lack of requests";
+
     /**
      * Constructs a MissingBackpressureException without message or cause.
      */
@@ -35,4 +44,13 @@ public MissingBackpressureException(String message) {
         super(message);
     }
 
+    /**
+     * Constructs a new {@code MissingBackpressureException} with the
+     * default message {@value #DEFAULT_MESSAGE}.
+     * @return the new {@code MissingBackpressureException} instance.
+     * @since 3.1.6
+     */
+    public static MissingBackpressureException createDefault() {
+        return new MissingBackpressureException(DEFAULT_MESSAGE);
+    }
 }
diff --git a/src/main/java/io/reactivex/rxjava3/exceptions/QueueOverflowException.java b/src/main/java/io/reactivex/rxjava3/exceptions/QueueOverflowException.java
new file mode 100644
index 00000000000..bdd8a25e6f1
--- /dev/null
+++ b/src/main/java/io/reactivex/rxjava3/exceptions/QueueOverflowException.java
@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2016-present, RxJava Contributors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
+ * compliance with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is
+ * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
+ * the License for the specific language governing permissions and limitations under the License.
+ */
+
+package io.reactivex.rxjava3.exceptions;
+
+/**
+ * Indicates an overflow happened because the upstream disregarded backpressure completely or
+ * {@link org.reactivestreams.Subscriber#onNext(Object)} was called concurrently from multiple threads
+ * without synchronization. Rarely, it is an indication of bugs inside an operator.
+ * @since 3.1.6
+ */
+public final class QueueOverflowException extends RuntimeException {
+
+    private static final long serialVersionUID = 8517344746016032542L;
+
+    /**
+     * The message for queue overflows.
+     * 

+     * This can happen if the upstream disregards backpressure completely or calls
+     * {@link org.reactivestreams.Subscriber#onNext(Object)} concurrently from multiple threads
+     * without synchronization. Rarely, it is an indication of bugs inside an operator.
+     */
+    private static final String DEFAULT_MESSAGE = "Queue overflow due to illegal concurrent onNext calls or a bug in an operator";
+
+    /**
+     * Constructs a QueueOverflowException with the default message.
+     */
+    public QueueOverflowException() {
+        this(DEFAULT_MESSAGE);
+    }
+
+    /**
+     * Constructs a QueueOverflowException with the given message but no cause.
+     * @param message the error message
+     */
+    public QueueOverflowException(String message) {
+        super(message);
+    }
+}
diff --git a/src/main/java/io/reactivex/rxjava3/functions/Supplier.java b/src/main/java/io/reactivex/rxjava3/functions/Supplier.java
index fe43f0d8c8c..ebf7fdda6d9 100644
--- a/src/main/java/io/reactivex/rxjava3/functions/Supplier.java
+++ b/src/main/java/io/reactivex/rxjava3/functions/Supplier.java
@@ -13,8 +13,6 @@
 
 package io.reactivex.rxjava3.functions;
 
-import io.reactivex.rxjava3.annotations.NonNull;
-
 /**
  * A functional interface (callback) that provides a single value or
  * throws an exception.
@@ -25,7 +23,7 @@
  * @since 3.0.0
  */
 @FunctionalInterface
-public interface Supplier<@NonNull T> {
+public interface Supplier {
 
     /**
      * Produces a value or throws an exception.
diff --git a/src/main/java/io/reactivex/rxjava3/internal/jdk8/FlowableFlatMapStream.java b/src/main/java/io/reactivex/rxjava3/internal/jdk8/FlowableFlatMapStream.java
index 35292bb17ca..48ea8b6e5f0 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/jdk8/FlowableFlatMapStream.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/jdk8/FlowableFlatMapStream.java
@@ -174,7 +174,7 @@ public void onNext(T t) {
             if (sourceMode != QueueFuseable.ASYNC) {
                 if (!queue.offer(t)) {
                     upstream.cancel();
-                    onError(new MissingBackpressureException("Queue full?!"));
+                    onError(new QueueOverflowException());
                     return;
                 }
             }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/completable/CompletableConcat.java b/src/main/java/io/reactivex/rxjava3/internal/operators/completable/CompletableConcat.java
index d83ce2d398d..00a53f3ad73 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/completable/CompletableConcat.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/completable/CompletableConcat.java
@@ -120,7 +120,7 @@ public void onSubscribe(Subscription s) {
         public void onNext(CompletableSource t) {
             if (sourceFused == QueueSubscription.NONE) {
                 if (!queue.offer(t)) {
-                    onError(new MissingBackpressureException());
+                    onError(new QueueOverflowException());
                     return;
                 }
             }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/completable/CompletableOnErrorComplete.java b/src/main/java/io/reactivex/rxjava3/internal/operators/completable/CompletableOnErrorComplete.java
index bebb401e482..c4252e7f3b4 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/completable/CompletableOnErrorComplete.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/completable/CompletableOnErrorComplete.java
@@ -32,15 +32,18 @@ public CompletableOnErrorComplete(CompletableSource source, Predicate predicate;
 
-        OnError(CompletableObserver observer) {
+        OnError(CompletableObserver observer,
+                Predicate predicate) {
             this.downstream = observer;
+            this.predicate = predicate;
         }
 
         @Override
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/BlockingFlowableIterable.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/BlockingFlowableIterable.java
index a25032e33b6..11239d04a7a 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/BlockingFlowableIterable.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/BlockingFlowableIterable.java
@@ -138,9 +138,12 @@ public void onSubscribe(Subscription s) {
         @Override
         public void onNext(T t) {
             if (!queue.offer(t)) {
+                // Error must be set first before calling cancel to avoid race
+                // with hasNext(), which checks for cancel first before checking
+                // for error.
+                error = new QueueOverflowException();
                 SubscriptionHelper.cancel(this);
-
-                onError(new MissingBackpressureException("Queue full?!"));
+                onComplete();
             } else {
                 signalConsumer();
             }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableBufferExactBoundary.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableBufferExactBoundary.java
index e543272a39e..3e2abefdd98 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableBufferExactBoundary.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableBufferExactBoundary.java
@@ -45,7 +45,7 @@ protected void subscribeActual(Subscriber s) {
     }
 
     static final class BufferExactBoundarySubscriber, B>
-    extends QueueDrainSubscriber implements FlowableSubscriber, Subscription, Disposable {
+    extends QueueDrainSubscriber implements Subscription, Disposable {
 
         final Supplier bufferSupplier;
         final Publisher boundary;
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableConcatMap.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableConcatMap.java
index bf0f0ff1638..5d1b6e4c33b 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableConcatMap.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableConcatMap.java
@@ -19,7 +19,7 @@
 import org.reactivestreams.*;
 
 import io.reactivex.rxjava3.core.*;
-import io.reactivex.rxjava3.exceptions.Exceptions;
+import io.reactivex.rxjava3.exceptions.*;
 import io.reactivex.rxjava3.functions.*;
 import io.reactivex.rxjava3.internal.subscriptions.*;
 import io.reactivex.rxjava3.internal.util.*;
@@ -152,7 +152,7 @@ public final void onNext(T t) {
             if (sourceMode != QueueSubscription.ASYNC) {
                 if (!queue.offer(t)) {
                     upstream.cancel();
-                    onError(new IllegalStateException("Queue full?!"));
+                    onError(new QueueOverflowException());
                     return;
                 }
             }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableConcatMapEager.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableConcatMapEager.java
index af33ec92814..dc423d89fc0 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableConcatMapEager.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableConcatMapEager.java
@@ -200,7 +200,7 @@ public void innerNext(InnerQueuedSubscriber inner, R value) {
                 drain();
             } else {
                 inner.cancel();
-                innerError(inner, new MissingBackpressureException());
+                innerError(inner, MissingBackpressureException.createDefault());
             }
         }
 
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableConcatMapScheduler.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableConcatMapScheduler.java
index c53ebe0867b..707d10a19ea 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableConcatMapScheduler.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableConcatMapScheduler.java
@@ -19,7 +19,7 @@
 import org.reactivestreams.*;
 
 import io.reactivex.rxjava3.core.*;
-import io.reactivex.rxjava3.exceptions.Exceptions;
+import io.reactivex.rxjava3.exceptions.*;
 import io.reactivex.rxjava3.functions.*;
 import io.reactivex.rxjava3.internal.operators.flowable.FlowableConcatMap.*;
 import io.reactivex.rxjava3.internal.subscriptions.SubscriptionHelper;
@@ -151,7 +151,7 @@ public final void onNext(T t) {
             if (sourceMode != QueueSubscription.ASYNC) {
                 if (!queue.offer(t)) {
                     upstream.cancel();
-                    onError(new IllegalStateException("Queue full?!"));
+                    onError(new QueueOverflowException());
                     return;
                 }
             }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableCreate.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableCreate.java
index 673fc4bc22d..1e87c4b7e65 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableCreate.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableCreate.java
@@ -442,7 +442,7 @@ static final class ErrorAsyncEmitter extends NoOverflowBaseAsyncEmitter {
 
         @Override
         void onOverflow() {
-            onError(new MissingBackpressureException("create: could not emit value due to lack of requests"));
+            onError(new MissingBackpressureException("create: " + MissingBackpressureException.DEFAULT_MESSAGE));
         }
 
     }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableDebounce.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableDebounce.java
index b1066c01337..51838a18645 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableDebounce.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableDebounce.java
@@ -148,7 +148,7 @@ void emit(long idx, T value) {
                     BackpressureHelper.produced(this, 1);
                 } else {
                     cancel();
-                    downstream.onError(new MissingBackpressureException("Could not deliver value due to lack of requests"));
+                    downstream.onError(MissingBackpressureException.createDefault());
                 }
             }
         }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableDebounceTimed.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableDebounceTimed.java
index 35bfaec397e..b9e5dff7f31 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableDebounceTimed.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableDebounceTimed.java
@@ -16,6 +16,8 @@
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.*;
 
+import io.reactivex.rxjava3.exceptions.Exceptions;
+import io.reactivex.rxjava3.functions.Consumer;
 import org.reactivestreams.*;
 
 import io.reactivex.rxjava3.core.*;
@@ -32,19 +34,20 @@ public final class FlowableDebounceTimed extends AbstractFlowableWithUpstream
     final long timeout;
     final TimeUnit unit;
     final Scheduler scheduler;
+    final Consumer onDropped;
 
-    public FlowableDebounceTimed(Flowable source, long timeout, TimeUnit unit, Scheduler scheduler) {
+    public FlowableDebounceTimed(Flowable source, long timeout, TimeUnit unit, Scheduler scheduler, Consumer onDropped) {
         super(source);
         this.timeout = timeout;
         this.unit = unit;
         this.scheduler = scheduler;
+        this.onDropped = onDropped;
     }
 
     @Override
     protected void subscribeActual(Subscriber s) {
         source.subscribe(new DebounceTimedSubscriber<>(
-                new SerializedSubscriber<>(s),
-                timeout, unit, scheduler.createWorker()));
+                new SerializedSubscriber<>(s), timeout, unit, scheduler.createWorker(), onDropped));
     }
 
     static final class DebounceTimedSubscriber extends AtomicLong
@@ -55,20 +58,22 @@ static final class DebounceTimedSubscriber extends AtomicLong
         final long timeout;
         final TimeUnit unit;
         final Scheduler.Worker worker;
+        final Consumer onDropped;
 
         Subscription upstream;
 
-        Disposable timer;
+        DebounceEmitter timer;
 
         volatile long index;
 
         boolean done;
 
-        DebounceTimedSubscriber(Subscriber actual, long timeout, TimeUnit unit, Worker worker) {
+        DebounceTimedSubscriber(Subscriber actual, long timeout, TimeUnit unit, Worker worker, Consumer onDropped) {
             this.downstream = actual;
             this.timeout = timeout;
             this.unit = unit;
             this.worker = worker;
+            this.onDropped = onDropped;
         }
 
         @Override
@@ -88,15 +93,26 @@ public void onNext(T t) {
             long idx = index + 1;
             index = idx;
 
-            Disposable d = timer;
-            if (d != null) {
-                d.dispose();
+            DebounceEmitter currentEmitter = timer;
+            if (currentEmitter != null) {
+                currentEmitter.dispose();
+            }
+
+            if (onDropped != null && currentEmitter != null) {
+                try {
+                    onDropped.accept(currentEmitter.value);
+                } catch (Throwable ex) {
+                    Exceptions.throwIfFatal(ex);
+                    upstream.cancel();
+                    done = true;
+                    downstream.onError(ex);
+                    worker.dispose();
+                }
             }
 
-            DebounceEmitter de = new DebounceEmitter<>(t, idx, this);
-            timer = de;
-            d = worker.schedule(de, timeout, unit);
-            de.setResource(d);
+            DebounceEmitter newEmitter = new DebounceEmitter<>(t, idx, this);
+            timer = newEmitter;
+            newEmitter.setResource(worker.schedule(newEmitter, timeout, unit));
         }
 
         @Override
@@ -121,15 +137,13 @@ public void onComplete() {
             }
             done = true;
 
-            Disposable d = timer;
+            DebounceEmitter d = timer;
             if (d != null) {
                 d.dispose();
             }
 
-            @SuppressWarnings("unchecked")
-            DebounceEmitter de = (DebounceEmitter)d;
-            if (de != null) {
-                de.emit();
+            if (d != null) {
+                d.emit();
             }
 
             downstream.onComplete();
@@ -159,7 +173,7 @@ void emit(long idx, T t, DebounceEmitter emitter) {
                     emitter.dispose();
                 } else {
                     cancel();
-                    downstream.onError(new MissingBackpressureException("Could not deliver value due to lack of requests"));
+                    downstream.onError(MissingBackpressureException.createDefault());
                 }
             }
         }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableDelay.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableDelay.java
index 469d0dd48b4..a7de73213ae 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableDelay.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableDelay.java
@@ -111,7 +111,9 @@ final class OnNext implements Runnable {
 
             @Override
             public void run() {
-                downstream.onNext(t);
+                if (!w.isDisposed()) {
+                    downstream.onNext(t);
+                }
             }
         }
 
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableFlatMap.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableFlatMap.java
index 78c9a9e5426..c250d3b1651 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableFlatMap.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableFlatMap.java
@@ -243,7 +243,7 @@ void tryEmitScalar(U value) {
                         q = getMainQueue();
                     }
                     if (!q.offer(value)) {
-                        onError(new MissingBackpressureException("Scalar queue full?!"));
+                        onError(new QueueOverflowException());
                     }
                 }
                 if (decrementAndGet() == 0) {
@@ -252,7 +252,7 @@ void tryEmitScalar(U value) {
             } else {
                 SimpleQueue q = getMainQueue();
                 if (!q.offer(value)) {
-                    onError(new MissingBackpressureException("Scalar queue full?!"));
+                    onError(new QueueOverflowException());
                     return;
                 }
                 if (getAndIncrement() != 0) {
@@ -278,7 +278,7 @@ void tryEmit(U value, InnerSubscriber inner) {
                         inner.queue = q;
                     }
                     if (!q.offer(value)) {
-                        onError(new MissingBackpressureException("Inner queue full?!"));
+                        onError(new QueueOverflowException());
                     }
                 }
                 if (decrementAndGet() == 0) {
@@ -291,7 +291,7 @@ void tryEmit(U value, InnerSubscriber inner) {
                     inner.queue = q;
                 }
                 if (!q.offer(value)) {
-                    onError(new MissingBackpressureException("Inner queue full?!"));
+                    onError(new QueueOverflowException());
                     return;
                 }
                 if (getAndIncrement() != 0) {
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableFlattenIterable.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableFlattenIterable.java
index 019a1323297..0b9164e0cd6 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableFlattenIterable.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableFlattenIterable.java
@@ -180,7 +180,7 @@ public void onNext(T t) {
                 return;
             }
             if (fusionMode == NONE && !queue.offer(t)) {
-                onError(new MissingBackpressureException("Queue is full?!"));
+                onError(new QueueOverflowException());
                 return;
             }
             drain();
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableGroupBy.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableGroupBy.java
index 344b029018a..50e641ffc1c 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableGroupBy.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableGroupBy.java
@@ -168,7 +168,7 @@ public void onNext(T t) {
                     if (emittedGroups != get()) {
                         downstream.onNext(group);
                     } else {
-                        MissingBackpressureException mbe = new MissingBackpressureException(groupHangWarning(emittedGroups));
+                        MissingBackpressureException mbe = groupHangWarning(emittedGroups);
                         mbe.initCause(ex);
                         onError(mbe);
                         return;
@@ -194,13 +194,13 @@ public void onNext(T t) {
                     }
                 } else {
                     upstream.cancel();
-                    onError(new MissingBackpressureException(groupHangWarning(emittedGroups)));
+                    onError(groupHangWarning(emittedGroups));
                 }
             }
         }
 
-        static String groupHangWarning(long n) {
-            return "Unable to emit a new group (#" + n + ") due to lack of requests. Please make sure the downstream can always accept a new group as well as each group is consumed in order for the whole operator to be able to proceed.";
+        static MissingBackpressureException groupHangWarning(long n) {
+            return new MissingBackpressureException("Unable to emit a new group (#" + n + ") due to lack of requests. Please make sure the downstream can always accept a new group as well as each group is consumed in order for the whole operator to be able to proceed.");
         }
 
         @Override
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableGroupJoin.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableGroupJoin.java
index 3021b9ddc5e..c9619c48b70 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableGroupJoin.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableGroupJoin.java
@@ -276,7 +276,7 @@ void drain() {
                             a.onNext(w);
                             BackpressureHelper.produced(requested, 1);
                         } else {
-                            fail(new MissingBackpressureException("Could not emit value due to lack of requests"), a, q);
+                            fail(MissingBackpressureException.createDefault(), a, q);
                             return;
                         }
 
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableInterval.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableInterval.java
index 536e36c2eab..98fbe6dee16 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableInterval.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableInterval.java
@@ -93,7 +93,7 @@ public void run() {
                     downstream.onNext(count++);
                     BackpressureHelper.produced(this, 1);
                 } else {
-                    downstream.onError(new MissingBackpressureException("Can't deliver value " + count + " due to lack of requests"));
+                    downstream.onError(new MissingBackpressureException("Could not emit value " + count + " due to lack of requests"));
                     DisposableHelper.dispose(resource);
                 }
             }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableIntervalRange.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableIntervalRange.java
index 7c556acdac1..cfa605882df 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableIntervalRange.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableIntervalRange.java
@@ -114,7 +114,7 @@ public void run() {
                         decrementAndGet();
                     }
                 } else {
-                    downstream.onError(new MissingBackpressureException("Can't deliver value " + count + " due to lack of requests"));
+                    downstream.onError(new MissingBackpressureException("Could not emit value " + count + " due to lack of requests"));
                     DisposableHelper.dispose(resource);
                 }
             }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableJoin.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableJoin.java
index 2c269cee4d1..9cda3d457db 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableJoin.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableJoin.java
@@ -260,7 +260,7 @@ void drain() {
 
                                 e++;
                             } else {
-                                ExceptionHelper.addThrowable(error, new MissingBackpressureException("Could not emit value due to lack of requests"));
+                                ExceptionHelper.addThrowable(error, MissingBackpressureException.createDefault());
                                 q.clear();
                                 cancelAll();
                                 errorAll(a);
@@ -321,7 +321,7 @@ else if (mode == RIGHT_VALUE) {
 
                                 e++;
                             } else {
-                                ExceptionHelper.addThrowable(error, new MissingBackpressureException("Could not emit value due to lack of requests"));
+                                ExceptionHelper.addThrowable(error, MissingBackpressureException.createDefault());
                                 q.clear();
                                 cancelAll();
                                 errorAll(a);
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableObserveOn.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableObserveOn.java
index 4e9f83e41ec..576debbf2b7 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableObserveOn.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableObserveOn.java
@@ -113,7 +113,7 @@ public final void onNext(T t) {
             if (!queue.offer(t)) {
                 upstream.cancel();
 
-                error = new MissingBackpressureException("Queue is full?!");
+                error = new QueueOverflowException();
                 done = true;
             }
             trySchedule();
@@ -244,8 +244,7 @@ public final boolean isEmpty() {
         }
     }
 
-    static final class ObserveOnSubscriber extends BaseObserveOnSubscriber
-    implements FlowableSubscriber {
+    static final class ObserveOnSubscriber extends BaseObserveOnSubscriber {
 
         private static final long serialVersionUID = -4547113800637756442L;
 
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureBuffer.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureBuffer.java
index 8261df29dc2..db58b68a103 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureBuffer.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureBuffer.java
@@ -20,7 +20,7 @@
 import io.reactivex.rxjava3.annotations.Nullable;
 import io.reactivex.rxjava3.core.*;
 import io.reactivex.rxjava3.exceptions.*;
-import io.reactivex.rxjava3.functions.Action;
+import io.reactivex.rxjava3.functions.*;
 import io.reactivex.rxjava3.internal.subscriptions.*;
 import io.reactivex.rxjava3.internal.util.BackpressureHelper;
 import io.reactivex.rxjava3.operators.*;
@@ -30,19 +30,21 @@ public final class FlowableOnBackpressureBuffer extends AbstractFlowableWithU
     final boolean unbounded;
     final boolean delayError;
     final Action onOverflow;
+    final Consumer onDropped;
 
     public FlowableOnBackpressureBuffer(Flowable source, int bufferSize, boolean unbounded,
-            boolean delayError, Action onOverflow) {
+            boolean delayError, Action onOverflow, Consumer onDropped) {
         super(source);
         this.bufferSize = bufferSize;
         this.unbounded = unbounded;
         this.delayError = delayError;
         this.onOverflow = onOverflow;
+        this.onDropped = onDropped;
     }
 
     @Override
     protected void subscribeActual(Subscriber s) {
-        source.subscribe(new BackpressureBufferSubscriber<>(s, bufferSize, unbounded, delayError, onOverflow));
+        source.subscribe(new BackpressureBufferSubscriber<>(s, bufferSize, unbounded, delayError, onOverflow, onDropped));
     }
 
     static final class BackpressureBufferSubscriber extends BasicIntQueueSubscription implements FlowableSubscriber {
@@ -53,6 +55,7 @@ static final class BackpressureBufferSubscriber extends BasicIntQueueSubscrip
         final SimplePlainQueue queue;
         final boolean delayError;
         final Action onOverflow;
+        final Consumer onDropped;
 
         Subscription upstream;
 
@@ -66,10 +69,11 @@ static final class BackpressureBufferSubscriber extends BasicIntQueueSubscrip
         boolean outputFused;
 
         BackpressureBufferSubscriber(Subscriber actual, int bufferSize,
-                boolean unbounded, boolean delayError, Action onOverflow) {
+                boolean unbounded, boolean delayError, Action onOverflow, Consumer onDropped) {
             this.downstream = actual;
             this.onOverflow = onOverflow;
             this.delayError = delayError;
+            this.onDropped = onDropped;
 
             SimplePlainQueue q;
 
@@ -98,6 +102,7 @@ public void onNext(T t) {
                 MissingBackpressureException ex = new MissingBackpressureException("Buffer is full");
                 try {
                     onOverflow.run();
+                    onDropped.accept(t);
                 } catch (Throwable e) {
                     Exceptions.throwIfFatal(e);
                     ex.initCause(e);
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureBufferStrategy.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureBufferStrategy.java
index 9b0b8a7b207..7963fb7d409 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureBufferStrategy.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureBufferStrategy.java
@@ -20,7 +20,7 @@
 
 import io.reactivex.rxjava3.core.*;
 import io.reactivex.rxjava3.exceptions.*;
-import io.reactivex.rxjava3.functions.Action;
+import io.reactivex.rxjava3.functions.*;
 import io.reactivex.rxjava3.internal.subscriptions.SubscriptionHelper;
 import io.reactivex.rxjava3.internal.util.BackpressureHelper;
 import io.reactivex.rxjava3.plugins.RxJavaPlugins;
@@ -38,17 +38,21 @@ public final class FlowableOnBackpressureBufferStrategy extends AbstractFlowa
 
     final BackpressureOverflowStrategy strategy;
 
+    final Consumer onDropped;
+
     public FlowableOnBackpressureBufferStrategy(Flowable source,
-            long bufferSize, Action onOverflow, BackpressureOverflowStrategy strategy) {
+            long bufferSize, Action onOverflow, BackpressureOverflowStrategy strategy,
+            Consumer onDropped) {
         super(source);
         this.bufferSize = bufferSize;
         this.onOverflow = onOverflow;
         this.strategy = strategy;
+        this.onDropped = onDropped;
     }
 
     @Override
     protected void subscribeActual(Subscriber s) {
-        source.subscribe(new OnBackpressureBufferStrategySubscriber<>(s, onOverflow, strategy, bufferSize));
+        source.subscribe(new OnBackpressureBufferStrategySubscriber<>(s, onOverflow, strategy, bufferSize, onDropped));
     }
 
     static final class OnBackpressureBufferStrategySubscriber
@@ -61,6 +65,8 @@ static final class OnBackpressureBufferStrategySubscriber
 
         final Action onOverflow;
 
+        final Consumer onDropped;
+
         final BackpressureOverflowStrategy strategy;
 
         final long bufferSize;
@@ -77,13 +83,15 @@ static final class OnBackpressureBufferStrategySubscriber
         Throwable error;
 
         OnBackpressureBufferStrategySubscriber(Subscriber actual, Action onOverflow,
-                BackpressureOverflowStrategy strategy, long bufferSize) {
+                BackpressureOverflowStrategy strategy, long bufferSize,
+                Consumer onDropped) {
             this.downstream = actual;
             this.onOverflow = onOverflow;
             this.strategy = strategy;
             this.bufferSize = bufferSize;
             this.requested = new AtomicLong();
             this.deque = new ArrayDeque<>();
+            this.onDropped = onDropped;
         }
 
         @Override
@@ -104,44 +112,60 @@ public void onNext(T t) {
             }
             boolean callOnOverflow = false;
             boolean callError = false;
+            boolean callDrain = false;
             Deque dq = deque;
+            T toDrop = null;
             synchronized (dq) {
                if (dq.size() == bufferSize) {
                    switch (strategy) {
                    case DROP_LATEST:
-                       dq.pollLast();
+                       toDrop = dq.pollLast();
                        dq.offer(t);
                        callOnOverflow = true;
                        break;
                    case DROP_OLDEST:
-                       dq.poll();
+                       toDrop = dq.poll();
                        dq.offer(t);
                        callOnOverflow = true;
                        break;
                    default:
                        // signal error
+                       toDrop = t;
                        callError = true;
                        break;
                    }
                } else {
                    dq.offer(t);
+                   callDrain = true;
                }
             }
 
-            if (callOnOverflow) {
-                if (onOverflow != null) {
-                    try {
-                        onOverflow.run();
-                    } catch (Throwable ex) {
-                        Exceptions.throwIfFatal(ex);
-                        upstream.cancel();
-                        onError(ex);
-                    }
+            if (callOnOverflow && onOverflow != null) {
+                try {
+                    onOverflow.run();
+                } catch (Throwable ex) {
+                    Exceptions.throwIfFatal(ex);
+                    upstream.cancel();
+                    onError(ex);
+                }
+            }
+
+            if (onDropped != null && toDrop != null) {
+                try {
+                    onDropped.accept(toDrop);
+                } catch (Throwable ex) {
+                    Exceptions.throwIfFatal(ex);
+                    upstream.cancel();
+                    onError(ex);
                 }
-            } else if (callError) {
+            }
+
+            if (callError) {
                 upstream.cancel();
-                onError(new MissingBackpressureException());
-            } else {
+                onError(MissingBackpressureException.createDefault());
+            }
+
+            if (callDrain) {
                 drain();
             }
         }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureError.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureError.java
index 03e668b2ba0..acaf165069f 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureError.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureError.java
@@ -66,7 +66,7 @@ public void onNext(T t) {
                 BackpressureHelper.produced(this, 1);
             } else {
                 upstream.cancel();
-                onError(new MissingBackpressureException("could not emit value due to lack of requests"));
+                onError(MissingBackpressureException.createDefault());
             }
         }
 
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureLatest.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureLatest.java
index 1a98831bd2c..155e284e93a 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureLatest.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureLatest.java
@@ -14,30 +14,48 @@
 package io.reactivex.rxjava3.internal.operators.flowable;
 
 import io.reactivex.rxjava3.core.Flowable;
+import io.reactivex.rxjava3.exceptions.Exceptions;
+import io.reactivex.rxjava3.functions.Consumer;
 import org.reactivestreams.Subscriber;
 
 public final class FlowableOnBackpressureLatest extends AbstractFlowableWithUpstream {
 
-    public FlowableOnBackpressureLatest(Flowable source) {
+    final Consumer onDropped;
+
+    public FlowableOnBackpressureLatest(Flowable source, Consumer onDropped) {
         super(source);
+        this.onDropped = onDropped;
     }
 
     @Override
     protected void subscribeActual(Subscriber s) {
-        source.subscribe(new BackpressureLatestSubscriber<>(s));
+        source.subscribe(new BackpressureLatestSubscriber<>(s, onDropped));
     }
 
     static final class BackpressureLatestSubscriber extends AbstractBackpressureThrottlingSubscriber {
 
         private static final long serialVersionUID = 163080509307634843L;
 
-        BackpressureLatestSubscriber(Subscriber downstream) {
+        final Consumer onDropped;
+
+        BackpressureLatestSubscriber(Subscriber downstream,
+                                     Consumer onDropped) {
             super(downstream);
+            this.onDropped = onDropped;
         }
 
         @Override
         public void onNext(T t) {
-            current.lazySet(t);
+            T oldValue = current.getAndSet(t);
+            if (onDropped != null && oldValue != null) {
+                try {
+                    onDropped.accept(oldValue);
+                } catch (Throwable ex) {
+                    Exceptions.throwIfFatal(ex);
+                    upstream.cancel();
+                    downstream.onError(ex);
+                }
+            }
             drain();
         }
     }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowablePublish.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowablePublish.java
index 87f43b762b3..b05bc8b748b 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowablePublish.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowablePublish.java
@@ -226,7 +226,7 @@ public void onSubscribe(Subscription s) {
         public void onNext(T t) {
             // we expect upstream to honor backpressure requests
             if (sourceMode == QueueSubscription.NONE && !queue.offer(t)) {
-                onError(new MissingBackpressureException("Prefetch queue is full?!"));
+                onError(new QueueOverflowException());
                 return;
             }
             // since many things can happen concurrently, we have a common dispatch
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowablePublishMulticast.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowablePublishMulticast.java
index c97b8b6bbfc..08d0e400586 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowablePublishMulticast.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowablePublishMulticast.java
@@ -212,7 +212,7 @@ public void onNext(T t) {
             }
             if (sourceMode == QueueSubscription.NONE && !queue.offer(t)) {
                 upstream.get().cancel();
-                onError(new MissingBackpressureException());
+                onError(MissingBackpressureException.createDefault());
                 return;
             }
             drain();
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableSamplePublisher.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableSamplePublisher.java
index 778f3faf219..19474d2cc0f 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableSamplePublisher.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableSamplePublisher.java
@@ -129,7 +129,7 @@ void emit() {
                     BackpressureHelper.produced(requested, 1);
                 } else {
                     cancel();
-                    downstream.onError(new MissingBackpressureException("Couldn't emit value due to lack of requests!"));
+                    downstream.onError(MissingBackpressureException.createDefault());
                 }
             }
         }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableSampleTimed.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableSampleTimed.java
index e17ad04a667..40551f4a8ed 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableSampleTimed.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableSampleTimed.java
@@ -16,6 +16,8 @@
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.*;
 
+import io.reactivex.rxjava3.exceptions.Exceptions;
+import io.reactivex.rxjava3.functions.Consumer;
 import org.reactivestreams.*;
 
 import io.reactivex.rxjava3.core.*;
@@ -29,24 +31,25 @@ public final class FlowableSampleTimed extends AbstractFlowableWithUpstream onDropped;
 
-    public FlowableSampleTimed(Flowable source, long period, TimeUnit unit, Scheduler scheduler, boolean emitLast) {
+    public FlowableSampleTimed(Flowable source, long period, TimeUnit unit, Scheduler scheduler, boolean emitLast, Consumer onDropped) {
         super(source);
         this.period = period;
         this.unit = unit;
         this.scheduler = scheduler;
         this.emitLast = emitLast;
+        this.onDropped = onDropped;
     }
 
     @Override
     protected void subscribeActual(Subscriber s) {
         SerializedSubscriber serial = new SerializedSubscriber<>(s);
         if (emitLast) {
-            source.subscribe(new SampleTimedEmitLast<>(serial, period, unit, scheduler));
+            source.subscribe(new SampleTimedEmitLast<>(serial, period, unit, scheduler, onDropped));
         } else {
-            source.subscribe(new SampleTimedNoLast<>(serial, period, unit, scheduler));
+            source.subscribe(new SampleTimedNoLast<>(serial, period, unit, scheduler, onDropped));
         }
     }
 
@@ -58,6 +61,7 @@ abstract static class SampleTimedSubscriber extends AtomicReference implem
         final long period;
         final TimeUnit unit;
         final Scheduler scheduler;
+        final Consumer onDropped;
 
         final AtomicLong requested = new AtomicLong();
 
@@ -65,11 +69,12 @@ abstract static class SampleTimedSubscriber extends AtomicReference implem
 
         Subscription upstream;
 
-        SampleTimedSubscriber(Subscriber actual, long period, TimeUnit unit, Scheduler scheduler) {
+        SampleTimedSubscriber(Subscriber actual, long period, TimeUnit unit, Scheduler scheduler, Consumer onDropped) {
             this.downstream = actual;
             this.period = period;
             this.unit = unit;
             this.scheduler = scheduler;
+            this.onDropped = onDropped;
         }
 
         @Override
@@ -84,7 +89,17 @@ public void onSubscribe(Subscription s) {
 
         @Override
         public void onNext(T t) {
-            lazySet(t);
+            T oldValue = getAndSet(t);
+            if (oldValue != null && onDropped != null) {
+              try {
+                  onDropped.accept(oldValue);
+              } catch (Throwable throwable) {
+                  Exceptions.throwIfFatal(throwable);
+                  cancelTimer();
+                  upstream.cancel();
+                  downstream.onError(throwable);
+              }
+            }
         }
 
         @Override
@@ -125,7 +140,7 @@ void emit() {
                     BackpressureHelper.produced(requested, 1);
                 } else {
                     cancel();
-                    downstream.onError(new MissingBackpressureException("Couldn't emit value due to lack of requests!"));
+                    downstream.onError(MissingBackpressureException.createDefault());
                 }
             }
         }
@@ -137,8 +152,8 @@ static final class SampleTimedNoLast extends SampleTimedSubscriber {
 
         private static final long serialVersionUID = -7139995637533111443L;
 
-        SampleTimedNoLast(Subscriber actual, long period, TimeUnit unit, Scheduler scheduler) {
-            super(actual, period, unit, scheduler);
+        SampleTimedNoLast(Subscriber actual, long period, TimeUnit unit, Scheduler scheduler, Consumer onDropped) {
+            super(actual, period, unit, scheduler, onDropped);
         }
 
         @Override
@@ -158,8 +173,8 @@ static final class SampleTimedEmitLast extends SampleTimedSubscriber {
 
         final AtomicInteger wip;
 
-        SampleTimedEmitLast(Subscriber actual, long period, TimeUnit unit, Scheduler scheduler) {
-            super(actual, period, unit, scheduler);
+        SampleTimedEmitLast(Subscriber actual, long period, TimeUnit unit, Scheduler scheduler, Consumer onDropped) {
+            super(actual, period, unit, scheduler, onDropped);
             this.wip = new AtomicInteger(1);
         }
 
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableSequenceEqual.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableSequenceEqual.java
index 0ba38698d6a..8dadbe01617 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableSequenceEqual.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableSequenceEqual.java
@@ -300,7 +300,7 @@ public void onSubscribe(Subscription s) {
         public void onNext(T t) {
             if (sourceMode == QueueSubscription.NONE) {
                 if (!queue.offer(t)) {
-                    onError(new MissingBackpressureException());
+                    onError(MissingBackpressureException.createDefault());
                     return;
                 }
             }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableSwitchMap.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableSwitchMap.java
index 1c820570dc3..4d4521c655a 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableSwitchMap.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableSwitchMap.java
@@ -381,7 +381,7 @@ public void onNext(R t) {
             SwitchMapSubscriber p = parent;
             if (index == p.unique) {
                 if (fusionMode == QueueSubscription.NONE && !queue.offer(t)) {
-                    onError(new MissingBackpressureException("Queue full?!"));
+                    onError(new QueueOverflowException());
                     return;
                 }
                 p.drain();
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableThrottleFirstTimed.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableThrottleFirstTimed.java
index c12399e1d1d..44499ec2556 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableThrottleFirstTimed.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableThrottleFirstTimed.java
@@ -16,6 +16,8 @@
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicLong;
 
+import io.reactivex.rxjava3.exceptions.Exceptions;
+import io.reactivex.rxjava3.functions.Consumer;
 import org.reactivestreams.*;
 
 import io.reactivex.rxjava3.core.*;
@@ -32,44 +34,53 @@ public final class FlowableThrottleFirstTimed extends AbstractFlowableWithUps
     final long timeout;
     final TimeUnit unit;
     final Scheduler scheduler;
+    final Consumer onDropped;
 
-    public FlowableThrottleFirstTimed(Flowable source, long timeout, TimeUnit unit, Scheduler scheduler) {
+    public FlowableThrottleFirstTimed(Flowable source,
+                                      long timeout,
+                                      TimeUnit unit,
+                                      Scheduler scheduler,
+                                      Consumer onDropped) {
         super(source);
         this.timeout = timeout;
         this.unit = unit;
         this.scheduler = scheduler;
+        this.onDropped = onDropped;
     }
 
     @Override
     protected void subscribeActual(Subscriber s) {
         source.subscribe(new DebounceTimedSubscriber<>(
                 new SerializedSubscriber<>(s),
-                timeout, unit, scheduler.createWorker()));
+                timeout, unit, scheduler.createWorker(),
+                onDropped));
     }
 
     static final class DebounceTimedSubscriber
     extends AtomicLong
     implements FlowableSubscriber, Subscription, Runnable {
-
         private static final long serialVersionUID = -9102637559663639004L;
+
         final Subscriber downstream;
         final long timeout;
         final TimeUnit unit;
         final Scheduler.Worker worker;
-
+        final Consumer onDropped;
         Subscription upstream;
-
         final SequentialDisposable timer = new SequentialDisposable();
-
         volatile boolean gate;
-
         boolean done;
 
-        DebounceTimedSubscriber(Subscriber actual, long timeout, TimeUnit unit, Worker worker) {
+        DebounceTimedSubscriber(Subscriber actual,
+                                long timeout,
+                                TimeUnit unit,
+                                Worker worker,
+                                Consumer onDropped) {
             this.downstream = actual;
             this.timeout = timeout;
             this.unit = unit;
             this.worker = worker;
+            this.onDropped = onDropped;
         }
 
         @Override
@@ -94,9 +105,10 @@ public void onNext(T t) {
                     downstream.onNext(t);
                     BackpressureHelper.produced(this, 1);
                 } else {
+                    upstream.cancel();
                     done = true;
-                    cancel();
-                    downstream.onError(new MissingBackpressureException("Could not deliver value due to lack of requests"));
+                    downstream.onError(MissingBackpressureException.createDefault());
+                    worker.dispose();
                     return;
                 }
 
@@ -106,6 +118,16 @@ public void onNext(T t) {
                 }
 
                 timer.replace(worker.schedule(this, timeout, unit));
+            } else if (onDropped != null) {
+                try {
+                    onDropped.accept(t);
+                } catch (Throwable ex) {
+                    Exceptions.throwIfFatal(ex);
+                    upstream.cancel();
+                    done = true;
+                    downstream.onError(ex);
+                    worker.dispose();
+                }
             }
         }
 
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableThrottleLatest.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableThrottleLatest.java
index e6cb5ffdcca..e28e5f09dfe 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableThrottleLatest.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableThrottleLatest.java
@@ -19,9 +19,11 @@
 import org.reactivestreams.*;
 
 import io.reactivex.rxjava3.core.*;
-import io.reactivex.rxjava3.exceptions.MissingBackpressureException;
+import io.reactivex.rxjava3.exceptions.*;
+import io.reactivex.rxjava3.functions.Consumer;
 import io.reactivex.rxjava3.internal.subscriptions.SubscriptionHelper;
 import io.reactivex.rxjava3.internal.util.BackpressureHelper;
+import io.reactivex.rxjava3.plugins.RxJavaPlugins;
 
 /**
  * Emits the next or latest item when the given time elapses.
@@ -44,19 +46,24 @@ public final class FlowableThrottleLatest extends AbstractFlowableWithUpstrea
 
     final boolean emitLast;
 
+    final Consumer onDropped;
+
     public FlowableThrottleLatest(Flowable source,
-            long timeout, TimeUnit unit, Scheduler scheduler,
-            boolean emitLast) {
+            long timeout, TimeUnit unit,
+            Scheduler scheduler,
+            boolean emitLast,
+            Consumer onDropped) {
         super(source);
         this.timeout = timeout;
         this.unit = unit;
         this.scheduler = scheduler;
         this.emitLast = emitLast;
+        this.onDropped = onDropped;
     }
 
     @Override
     protected void subscribeActual(Subscriber s) {
-        source.subscribe(new ThrottleLatestSubscriber<>(s, timeout, unit, scheduler.createWorker(), emitLast));
+        source.subscribe(new ThrottleLatestSubscriber<>(s, timeout, unit, scheduler.createWorker(), emitLast, onDropped));
     }
 
     static final class ThrottleLatestSubscriber
@@ -79,6 +86,8 @@ static final class ThrottleLatestSubscriber
 
         final AtomicLong requested;
 
+        final Consumer onDropped;
+
         Subscription upstream;
 
         volatile boolean done;
@@ -93,8 +102,10 @@ static final class ThrottleLatestSubscriber
         boolean timerRunning;
 
         ThrottleLatestSubscriber(Subscriber downstream,
-                long timeout, TimeUnit unit, Scheduler.Worker worker,
-                boolean emitLast) {
+                long timeout, TimeUnit unit,
+                Scheduler.Worker worker,
+                boolean emitLast,
+                Consumer onDropped) {
             this.downstream = downstream;
             this.timeout = timeout;
             this.unit = unit;
@@ -102,6 +113,7 @@ static final class ThrottleLatestSubscriber
             this.emitLast = emitLast;
             this.latest = new AtomicReference<>();
             this.requested = new AtomicLong();
+            this.onDropped = onDropped;
         }
 
         @Override
@@ -115,7 +127,17 @@ public void onSubscribe(Subscription s) {
 
         @Override
         public void onNext(T t) {
-            latest.set(t);
+            T old = latest.getAndSet(t);
+            if (onDropped != null && old != null) {
+                try {
+                    onDropped.accept(old);
+                } catch (Throwable ex) {
+                    Exceptions.throwIfFatal(ex);
+                    upstream.cancel();
+                    error = ex;
+                    done = true;
+                }
+            }
             drain();
         }
 
@@ -145,6 +167,22 @@ public void cancel() {
             upstream.cancel();
             worker.dispose();
             if (getAndIncrement() == 0) {
+                clear();
+            }
+        }
+
+        void clear() {
+            if (onDropped != null) {
+                T v = latest.getAndSet(null);
+                if (v != null) {
+                    try {
+                        onDropped.accept(v);
+                    } catch (Throwable ex) {
+                        Exceptions.throwIfFatal(ex);
+                        RxJavaPlugins.onError(ex);
+                    }
+                }
+            } else {
                 latest.lazySet(null);
             }
         }
@@ -170,14 +208,27 @@ void drain() {
 
                 for (;;) {
                     if (cancelled) {
-                        latest.lazySet(null);
+                        clear();
                         return;
                     }
 
                     boolean d = done;
+                    Throwable error = this.error;
 
                     if (d && error != null) {
-                        latest.lazySet(null);
+                        if (onDropped != null) {
+                            T v = latest.getAndSet(null);
+                            if (v != null) {
+                                try {
+                                    onDropped.accept(v);
+                                } catch (Throwable ex) {
+                                    Exceptions.throwIfFatal(ex);
+                                    error = new CompositeException(error, ex);
+                                }
+                            }
+                        } else {
+                            latest.lazySet(null);
+                        }
                         downstream.onError(error);
                         worker.dispose();
                         return;
@@ -187,19 +238,31 @@ void drain() {
                     boolean empty = v == null;
 
                     if (d) {
-                        if (!empty && emitLast) {
+                        if (!empty) {
                             v = latest.getAndSet(null);
-                            long e = emitted;
-                            if (e != requested.get()) {
-                                emitted = e + 1;
-                                downstream.onNext(v);
-                                downstream.onComplete();
+                            if (emitLast) {
+                                long e = emitted;
+                                if (e != requested.get()) {
+                                    emitted = e + 1;
+                                    downstream.onNext(v);
+                                    downstream.onComplete();
+                                } else {
+                                    tryDropAndSignalMBE(v);
+                                }
                             } else {
-                                downstream.onError(new MissingBackpressureException(
-                                        "Could not emit final value due to lack of requests"));
+                                if (onDropped != null) {
+                                    try {
+                                        onDropped.accept(v);
+                                    } catch (Throwable ex) {
+                                        Exceptions.throwIfFatal(ex);
+                                        downstream.onError(ex);
+                                        worker.dispose();
+                                        return;
+                                    }
+                                }
+                                downstream.onComplete();
                             }
                         } else {
-                            latest.lazySet(null);
                             downstream.onComplete();
                         }
                         worker.dispose();
@@ -222,8 +285,7 @@ void drain() {
                             emitted = e + 1;
                         } else {
                             upstream.cancel();
-                            downstream.onError(new MissingBackpressureException(
-                                    "Could not emit value due to lack of requests"));
+                            tryDropAndSignalMBE(v);
                             worker.dispose();
                             return;
                         }
@@ -242,5 +304,18 @@ void drain() {
                 }
             }
         }
+
+        void tryDropAndSignalMBE(T valueToDrop) {
+            Throwable errorToSignal = MissingBackpressureException.createDefault();
+            if (onDropped != null) {
+                try {
+                    onDropped.accept(valueToDrop);
+                } catch (Throwable ex) {
+                    Exceptions.throwIfFatal(ex);
+                    errorToSignal = new CompositeException(errorToSignal, ex);
+                }
+            }
+            downstream.onError(errorToSignal);
+        }
     }
 }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableTimer.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableTimer.java
index dd33daea0fb..db45fe2e98d 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableTimer.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableTimer.java
@@ -78,7 +78,7 @@ public void run() {
                     downstream.onComplete();
                 } else {
                     lazySet(EmptyDisposable.INSTANCE);
-                    downstream.onError(new MissingBackpressureException("Can't deliver value due to lack of requests"));
+                    downstream.onError(MissingBackpressureException.createDefault());
                 }
             }
         }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableToList.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableToList.java
index 2b7c19e2697..3f03d93112e 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableToList.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableToList.java
@@ -46,7 +46,7 @@ protected void subscribeActual(Subscriber s) {
 
     static final class ToListSubscriber>
     extends DeferredScalarSubscription
-    implements FlowableSubscriber, Subscription {
+    implements FlowableSubscriber {
 
         private static final long serialVersionUID = -8134157938864266736L;
         Subscription upstream;
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableWindowBoundary.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableWindowBoundary.java
index 1dcfd4e5293..2aad69dcb5e 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableWindowBoundary.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableWindowBoundary.java
@@ -248,7 +248,7 @@ void drain() {
                         } else {
                             SubscriptionHelper.cancel(upstream);
                             boundarySubscriber.dispose();
-                            errors.tryAddThrowableOrReport(new MissingBackpressureException("Could not deliver a window due to lack of requests"));
+                            errors.tryAddThrowableOrReport(MissingBackpressureException.createDefault());
                             done = true;
                         }
                     }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableWindowBoundarySelector.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableWindowBoundarySelector.java
index 394315cd9bf..d6bffae2e13 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableWindowBoundarySelector.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableWindowBoundarySelector.java
@@ -272,7 +272,7 @@ void drain() {
                                     upstream.cancel();
                                     startSubscriber.cancel();
                                     resources.dispose();
-                                    error.tryAddThrowableOrReport(new MissingBackpressureException(FlowableWindowTimed.missingBackpressureMessage(emitted)));
+                                    error.tryAddThrowableOrReport(FlowableWindowTimed.missingBackpressureMessage(emitted));
                                     upstreamDone = true;
                                 }
                             }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableWindowTimed.java b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableWindowTimed.java
index 23ef916fef9..39e7de59ada 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableWindowTimed.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableWindowTimed.java
@@ -213,7 +213,7 @@ void createFirstWindow() {
                     upstream.request(Long.MAX_VALUE);
                 } else {
                     upstream.cancel();
-                    downstream.onError(new MissingBackpressureException(missingBackpressureMessage(emitted)));
+                    downstream.onError(missingBackpressureMessage(emitted));
 
                     cleanupResources();
                     upstreamCancelled = true;
@@ -282,7 +282,7 @@ else if (!isEmpty) {
                                     cleanupResources();
                                     upstreamCancelled = true;
 
-                                    downstream.onError(new MissingBackpressureException(missingBackpressureMessage(emitted)));
+                                    downstream.onError(missingBackpressureMessage(emitted));
                                 } else {
                                     emitted++;
 
@@ -386,7 +386,7 @@ void createFirstWindow() {
                     upstream.request(Long.MAX_VALUE);
                 } else {
                     upstream.cancel();
-                    downstream.onError(new MissingBackpressureException(missingBackpressureMessage(emitted)));
+                    downstream.onError(missingBackpressureMessage(emitted));
 
                     cleanupResources();
                     upstreamCancelled = true;
@@ -499,7 +499,7 @@ UnicastProcessor createNewWindow(UnicastProcessor window) {
                     cleanupResources();
                     upstreamCancelled = true;
 
-                    downstream.onError(new MissingBackpressureException(missingBackpressureMessage(emitted)));
+                    downstream.onError(missingBackpressureMessage(emitted));
                 } else {
                     this.emitted = ++emitted;
 
@@ -584,7 +584,7 @@ void createFirstWindow() {
                     upstream.request(Long.MAX_VALUE);
                 } else {
                     upstream.cancel();
-                    downstream.onError(new MissingBackpressureException(missingBackpressureMessage(emitted)));
+                    downstream.onError(missingBackpressureMessage(emitted));
 
                     cleanupResources();
                     upstreamCancelled = true;
@@ -654,7 +654,7 @@ void drain() {
                                     }
                                 } else {
                                     upstream.cancel();
-                                    Throwable ex = new MissingBackpressureException(missingBackpressureMessage(emitted));
+                                    Throwable ex = missingBackpressureMessage(emitted);
                                     for (UnicastProcessor window : windows) {
                                         window.onError(ex);
                                     }
@@ -717,8 +717,8 @@ public void run() {
         }
     }
 
-    static String missingBackpressureMessage(long index) {
-        return "Unable to emit the next window (#" + index + ") due to lack of requests. Please make sure the downstream is ready to consume windows.";
+    static MissingBackpressureException missingBackpressureMessage(long index) {
+        return new MissingBackpressureException("Unable to emit the next window (#" + index + ") due to lack of requests. Please make sure the downstream is ready to consume windows.");
     }
 
 }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/mixed/ConcatMapXMainSubscriber.java b/src/main/java/io/reactivex/rxjava3/internal/operators/mixed/ConcatMapXMainSubscriber.java
index bd701de40c4..03e4c568d69 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/mixed/ConcatMapXMainSubscriber.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/mixed/ConcatMapXMainSubscriber.java
@@ -18,7 +18,7 @@
 import org.reactivestreams.Subscription;
 
 import io.reactivex.rxjava3.core.FlowableSubscriber;
-import io.reactivex.rxjava3.exceptions.MissingBackpressureException;
+import io.reactivex.rxjava3.exceptions.*;
 import io.reactivex.rxjava3.internal.subscriptions.SubscriptionHelper;
 import io.reactivex.rxjava3.internal.util.*;
 import io.reactivex.rxjava3.operators.QueueFuseable;
@@ -99,7 +99,7 @@ public final void onNext(T t) {
         if (t != null) {
             if (!queue.offer(t)) {
                 upstream.cancel();
-                onError(new MissingBackpressureException("queue full?!"));
+                onError(new QueueOverflowException());
                 return;
             }
         }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableBufferExactBoundary.java b/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableBufferExactBoundary.java
index 5892e092b96..bb650589085 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableBufferExactBoundary.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableBufferExactBoundary.java
@@ -43,7 +43,7 @@ protected void subscribeActual(Observer t) {
     }
 
     static final class BufferExactBoundaryObserver, B>
-    extends QueueDrainObserver implements Observer, Disposable {
+    extends QueueDrainObserver implements Disposable {
 
         final Supplier bufferSupplier;
         final ObservableSource boundary;
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableCache.java b/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableCache.java
index daa9edd533a..99e11259a6f 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableCache.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableCache.java
@@ -24,23 +24,7 @@
  *
  * @param  the source element type
  */
-public final class ObservableCache extends AbstractObservableWithUpstream
-implements Observer {
-
-    /**
-     * The subscription to the source should happen at most once.
-     */
-    final AtomicBoolean once;
-
-    /**
-     * The number of items per cached nodes.
-     */
-    final int capacityHint;
-
-    /**
-     * The current known array of observer state to notify.
-     */
-    final AtomicReference[]> observers;
+public final class ObservableCache extends AbstractObservableWithUpstream {
 
     /**
      * A shared instance of an empty array of observers to avoid creating
@@ -56,61 +40,49 @@ public final class ObservableCache extends AbstractObservableWithUpstream head;
-
-    /**
-     * The current tail of the linked structure holding the items.
-     */
-    Node tail;
-
-    /**
-     * How many items have been put into the tail node so far.
+     * The subscription to the source should happen at most once.
      */
-    int tailOffset;
+    final AtomicBoolean once;
 
     /**
-     * If {@link #observers} is {@link #TERMINATED}, this holds the terminal error if not null.
+     * Responsible caching events from the source and multicasting them to each downstream.
      */
-    Throwable error;
+    final Multicaster  multicaster;
 
     /**
-     * True if the source has terminated.
+     * The first node in a singly linked list. Each node has the capacity to hold a specific number of events, and each
+     * points exclusively to the next node (if present). When a new downstream arrives, the subscription is
+     * initialized with a reference to the "head" node, and any events present in the linked list are replayed. As
+     * events are replayed to the new downstream, its 'node' reference advances through the linked list, discarding each
+     * node reference once all events in that node have been replayed. Consequently, once {@code this} instance goes out
+     * of scope, the prefix of nodes up to the first node that is still being replayed becomes unreachable and eligible
+     * for collection.
      */
-    volatile boolean done;
+    final Node head;
 
     /**
      * Constructs an empty, non-connected cache.
      * @param source the source to subscribe to for the first incoming observer
      * @param capacityHint the number of items expected (reduce allocation frequency)
      */
-    @SuppressWarnings("unchecked")
     public ObservableCache(Observable source, int capacityHint) {
         super(source);
-        this.capacityHint = capacityHint;
         this.once = new AtomicBoolean();
         Node n = new Node<>(capacityHint);
         this.head = n;
-        this.tail = n;
-        this.observers = new AtomicReference<>(EMPTY);
+        this.multicaster = new Multicaster<>(capacityHint, n);
     }
 
     @Override
     protected void subscribeActual(Observer t) {
-        CacheDisposable consumer = new CacheDisposable<>(t, this);
+        CacheDisposable consumer = new CacheDisposable<>(t, multicaster, head);
         t.onSubscribe(consumer);
-        add(consumer);
+        multicaster.add(consumer);
 
         if (!once.get() && once.compareAndSet(false, true)) {
-            source.subscribe(this);
+            source.subscribe(multicaster);
         } else {
-            replay(consumer);
+            multicaster.replay(consumer);
         }
     }
 
@@ -127,7 +99,7 @@ protected void subscribeActual(Observer t) {
      * @return true if the cache has observers
      */
     /* public */ boolean hasObservers() {
-        return observers.get().length != 0;
+        return multicaster.get().length != 0;
     }
 
     /**
@@ -135,194 +107,241 @@ protected void subscribeActual(Observer t) {
      * @return the number of currently cached event count
      */
     /* public */ long cachedEventCount() {
-        return size;
+        return multicaster.size;
     }
 
-    /**
-     * Atomically adds the consumer to the {@link #observers} copy-on-write array
-     * if the source has not yet terminated.
-     * @param consumer the consumer to add
-     */
-    void add(CacheDisposable consumer) {
-        for (;;) {
-            CacheDisposable[] current = observers.get();
-            if (current == TERMINATED) {
-                return;
-            }
-            int n = current.length;
+    static final class Multicaster extends AtomicReference[]> implements Observer {
 
-            @SuppressWarnings("unchecked")
-            CacheDisposable[] next = new CacheDisposable[n + 1];
-            System.arraycopy(current, 0, next, 0, n);
-            next[n] = consumer;
+        /** */
+        private static final long serialVersionUID = 8514643269016498691L;
 
-            if (observers.compareAndSet(current, next)) {
-                return;
-            }
-        }
-    }
+        /**
+         * The number of items per cached nodes.
+         */
+        final int capacityHint;
 
-    /**
-     * Atomically removes the consumer from the {@link #observers} copy-on-write array.
-     * @param consumer the consumer to remove
-     */
-    @SuppressWarnings("unchecked")
-    void remove(CacheDisposable consumer) {
-        for (;;) {
-            CacheDisposable[] current = observers.get();
-            int n = current.length;
-            if (n == 0) {
-                return;
-            }
+        /**
+         * The total number of elements in the list available for reads.
+         */
+        volatile long size;
 
-            int j = -1;
-            for (int i = 0; i < n; i++) {
-                if (current[i] == consumer) {
-                    j = i;
-                    break;
-                }
-            }
+        /**
+         * The current tail of the linked structure holding the items.
+         */
+        Node tail;
 
-            if (j < 0) {
-                return;
-            }
-            CacheDisposable[] next;
+        /**
+         * How many items have been put into the tail node so far.
+         */
+        int tailOffset;
 
-            if (n == 1) {
-                next = EMPTY;
-            } else {
-                next = new CacheDisposable[n - 1];
-                System.arraycopy(current, 0, next, 0, j);
-                System.arraycopy(current, j + 1, next, j, n - j - 1);
-            }
+        /**
+         * If the observers are {@link #TERMINATED}, this holds the terminal error if not null.
+         */
+        Throwable error;
 
-            if (observers.compareAndSet(current, next)) {
-                return;
-            }
-        }
-    }
+        /**
+         * True if the source has terminated.
+         */
+        volatile boolean done;
 
-    /**
-     * Replays the contents of this cache to the given consumer based on its
-     * current state and number of items requested by it.
-     * @param consumer the consumer to continue replaying items to
-     */
-    void replay(CacheDisposable consumer) {
-        // make sure there is only one replay going on at a time
-        if (consumer.getAndIncrement() != 0) {
-            return;
+        @SuppressWarnings("unchecked")
+        Multicaster(int capacityHint, final Node head) {
+            super(EMPTY);
+            this.tail = head;
+            this.capacityHint = capacityHint;
         }
 
-        // see if there were more replay request in the meantime
-        int missed = 1;
-        // read out state into locals upfront to avoid being re-read due to volatile reads
-        long index = consumer.index;
-        int offset = consumer.offset;
-        Node node = consumer.node;
-        Observer downstream = consumer.downstream;
-        int capacity = capacityHint;
-
-        for (;;) {
-            // if the consumer got disposed, clear the node and quit
-            if (consumer.disposed) {
-                consumer.node = null;
-                return;
+        /**
+         * Atomically adds the consumer to the observers copy-on-write array
+         * if the source has not yet terminated.
+         * @param consumer the consumer to add
+         */
+        void add(CacheDisposable consumer) {
+            for (;;) {
+                CacheDisposable[] current = get();
+                if (current == TERMINATED) {
+                    return;
+                }
+                int n = current.length;
+
+                @SuppressWarnings("unchecked")
+                CacheDisposable[] next = new CacheDisposable[n + 1];
+                System.arraycopy(current, 0, next, 0, n);
+                next[n] = consumer;
+
+                if (compareAndSet(current, next)) {
+                    return;
+                }
             }
+        }
 
-            // first see if the source has terminated, read order matters!
-            boolean sourceDone = done;
-            // and if the number of items is the same as this consumer has received
-            boolean empty = size == index;
-
-            // if the source is done and we have all items so far, terminate the consumer
-            if (sourceDone && empty) {
-                // release the node object to avoid leaks through retained consumers
-                consumer.node = null;
-                // if error is not null then the source failed
-                Throwable ex = error;
-                if (ex != null) {
-                    downstream.onError(ex);
+        /**
+         * Atomically removes the consumer from the observers copy-on-write array.
+         * @param consumer the consumer to remove
+         */
+        @SuppressWarnings("unchecked")
+        void remove(CacheDisposable consumer) {
+            for (;;) {
+                CacheDisposable[] current = get();
+                int n = current.length;
+                if (n == 0) {
+                    return;
+                }
+
+                int j = -1;
+                for (int i = 0; i < n; i++) {
+                    if (current[i] == consumer) {
+                        j = i;
+                        break;
+                    }
+                }
+
+                if (j < 0) {
+                    return;
+                }
+                CacheDisposable[] next;
+
+                if (n == 1) {
+                    next = EMPTY;
                 } else {
-                    downstream.onComplete();
+                    next = new CacheDisposable[n - 1];
+                    System.arraycopy(current, 0, next, 0, j);
+                    System.arraycopy(current, j + 1, next, j, n - j - 1);
                 }
+
+                if (compareAndSet(current, next)) {
+                    return;
+                }
+            }
+        }
+
+        /**
+         * Replays the contents of this cache to the given consumer based on its
+         * current state and number of items requested by it.
+         * @param consumer the consumer to continue replaying items to
+         */
+        void replay(CacheDisposable consumer) {
+            // make sure there is only one replay going on at a time
+            if (consumer.getAndIncrement() != 0) {
                 return;
             }
 
-            // there are still items not sent to the consumer
-            if (!empty) {
-             // if the offset in the current node has reached the node capacity
-                if (offset == capacity) {
-                    // switch to the subsequent node
-                    node = node.next;
-                    // reset the in-node offset
-                    offset = 0;
+            // see if there were more replay request in the meantime
+            int missed = 1;
+            // read out state into locals upfront to avoid being re-read due to volatile reads
+            long index = consumer.index;
+            int offset = consumer.offset;
+            Node node = consumer.node;
+            Observer downstream = consumer.downstream;
+            int capacity = capacityHint;
+
+            for (;;) {
+                // if the consumer got disposed, clear the node and quit
+                if (consumer.disposed) {
+                    consumer.node = null;
+                    return;
                 }
 
-                // emit the cached item
-                downstream.onNext(node.values[offset]);
-
-                // move the node offset forward
-                offset++;
-                // move the total consumed item count forward
-                index++;
+                // first see if the source has terminated, read order matters!
+                boolean sourceDone = done;
+                // and if the number of items is the same as this consumer has received
+                boolean empty = size == index;
+
+                // if the source is done and we have all items so far, terminate the consumer
+                if (sourceDone && empty) {
+                    // release the node object to avoid leaks through retained consumers
+                    consumer.node = null;
+                    // if error is not null then the source failed
+                    Throwable ex = error;
+                    if (ex != null) {
+                        downstream.onError(ex);
+                    } else {
+                        downstream.onComplete();
+                    }
+                    return;
+                }
 
-                // retry for the next item/terminal event if any
-                continue;
-            }
+                // there are still items not sent to the consumer
+                if (!empty) {
+                 // if the offset in the current node has reached the node capacity
+                    if (offset == capacity) {
+                        // switch to the subsequent node
+                        node = node.next;
+                        // reset the in-node offset
+                        offset = 0;
+                    }
+
+                    // emit the cached item
+                    downstream.onNext(node.values[offset]);
+
+                    // move the node offset forward
+                    offset++;
+                    // move the total consumed item count forward
+                    index++;
+
+                    // retry for the next item/terminal event if any
+                    continue;
+                }
 
-            // commit the changed references back
-            consumer.index = index;
-            consumer.offset = offset;
-            consumer.node = node;
-            // release the changes and see if there were more replay request in the meantime
-            missed = consumer.addAndGet(-missed);
-            if (missed == 0) {
-                break;
+                // commit the changed references back
+                consumer.index = index;
+                consumer.offset = offset;
+                consumer.node = node;
+                // release the changes and see if there were more replay request in the meantime
+                missed = consumer.addAndGet(-missed);
+                if (missed == 0) {
+                    break;
+                }
             }
         }
-    }
 
-    @Override
-    public void onSubscribe(Disposable d) {
-        // we can't do much with the upstream disposable
-    }
-
-    @Override
-    public void onNext(T t) {
-        int tailOffset = this.tailOffset;
-        // if the current tail node is full, create a fresh node
-        if (tailOffset == capacityHint) {
-            Node n = new Node<>(tailOffset);
-            n.values[0] = t;
-            this.tailOffset = 1;
-            tail.next = n;
-            tail = n;
-        } else {
-            tail.values[tailOffset] = t;
-            this.tailOffset = tailOffset + 1;
+        @Override
+        public void onSubscribe(Disposable d) {
+            // we can't do much with the upstream disposable
         }
-        size++;
-        for (CacheDisposable consumer : observers.get()) {
-            replay(consumer);
+
+        @Override
+        public void onNext(T t) {
+            int tailOffset = this.tailOffset;
+            // if the current tail node is full, create a fresh node
+            if (tailOffset == capacityHint) {
+                Node n = new Node<>(tailOffset);
+                n.values[0] = t;
+                this.tailOffset = 1;
+                tail.next = n;
+                tail = n;
+            } else {
+                tail.values[tailOffset] = t;
+                this.tailOffset = tailOffset + 1;
+            }
+            size++;
+            for (CacheDisposable consumer : get()) {
+                replay(consumer);
+            }
         }
-    }
 
-    @SuppressWarnings("unchecked")
-    @Override
-    public void onError(Throwable t) {
-        error = t;
-        done = true;
-        for (CacheDisposable consumer : observers.getAndSet(TERMINATED)) {
-            replay(consumer);
+        @SuppressWarnings("unchecked")
+        @Override
+        public void onError(Throwable t) {
+            error = t;
+            done = true;
+            // No additional events will arrive, so now we can clear the 'tail' reference
+            tail = null;
+            for (CacheDisposable consumer : getAndSet(TERMINATED)) {
+                replay(consumer);
+            }
         }
-    }
 
-    @SuppressWarnings("unchecked")
-    @Override
-    public void onComplete() {
-        done = true;
-        for (CacheDisposable consumer : observers.getAndSet(TERMINATED)) {
-            replay(consumer);
+        @SuppressWarnings("unchecked")
+        @Override
+        public void onComplete() {
+            done = true;
+            // No additional events will arrive, so now we can clear the 'tail' reference
+            tail = null;
+            for (CacheDisposable consumer : getAndSet(TERMINATED)) {
+                replay(consumer);
+            }
         }
     }
 
@@ -338,7 +357,7 @@ static final class CacheDisposable extends AtomicInteger
 
         final Observer downstream;
 
-        final ObservableCache parent;
+        final Multicaster parent;
 
         Node node;
 
@@ -353,11 +372,12 @@ static final class CacheDisposable extends AtomicInteger
          * the parent cache object.
          * @param downstream the actual consumer
          * @param parent the parent that holds onto the cached items
+         * @param head the first node in the linked list
          */
-        CacheDisposable(Observer downstream, ObservableCache parent) {
+        CacheDisposable(Observer downstream, Multicaster parent, Node head) {
             this.downstream = downstream;
             this.parent = parent;
-            this.node = parent.head;
+            this.node = head;
         }
 
         @Override
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableDebounceTimed.java b/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableDebounceTimed.java
index 248d00ea23d..f2db191229f 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableDebounceTimed.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableDebounceTimed.java
@@ -19,6 +19,8 @@
 import io.reactivex.rxjava3.core.*;
 import io.reactivex.rxjava3.core.Scheduler.Worker;
 import io.reactivex.rxjava3.disposables.Disposable;
+import io.reactivex.rxjava3.exceptions.Exceptions;
+import io.reactivex.rxjava3.functions.Consumer;
 import io.reactivex.rxjava3.internal.disposables.DisposableHelper;
 import io.reactivex.rxjava3.observers.SerializedObserver;
 import io.reactivex.rxjava3.plugins.RxJavaPlugins;
@@ -27,19 +29,20 @@ public final class ObservableDebounceTimed extends AbstractObservableWithUpst
     final long timeout;
     final TimeUnit unit;
     final Scheduler scheduler;
+    final Consumer onDropped;
 
-    public ObservableDebounceTimed(ObservableSource source, long timeout, TimeUnit unit, Scheduler scheduler) {
+    public ObservableDebounceTimed(ObservableSource source, long timeout, TimeUnit unit, Scheduler scheduler, Consumer onDropped) {
         super(source);
         this.timeout = timeout;
         this.unit = unit;
         this.scheduler = scheduler;
+        this.onDropped = onDropped;
     }
 
     @Override
     public void subscribeActual(Observer t) {
         source.subscribe(new DebounceTimedObserver<>(
-                new SerializedObserver<>(t),
-                timeout, unit, scheduler.createWorker()));
+                new SerializedObserver<>(t), timeout, unit, scheduler.createWorker(), onDropped));
     }
 
     static final class DebounceTimedObserver
@@ -48,20 +51,22 @@ static final class DebounceTimedObserver
         final long timeout;
         final TimeUnit unit;
         final Scheduler.Worker worker;
+        final Consumer onDropped;
 
         Disposable upstream;
 
-        Disposable timer;
+        DebounceEmitter timer;
 
         volatile long index;
 
         boolean done;
 
-        DebounceTimedObserver(Observer actual, long timeout, TimeUnit unit, Worker worker) {
+        DebounceTimedObserver(Observer actual, long timeout, TimeUnit unit, Worker worker, Consumer onDropped) {
             this.downstream = actual;
             this.timeout = timeout;
             this.unit = unit;
             this.worker = worker;
+            this.onDropped = onDropped;
         }
 
         @Override
@@ -80,15 +85,25 @@ public void onNext(T t) {
             long idx = index + 1;
             index = idx;
 
-            Disposable d = timer;
-            if (d != null) {
-                d.dispose();
+            DebounceEmitter currentEmitter = timer;
+            if (currentEmitter != null) {
+                currentEmitter.dispose();
             }
 
-            DebounceEmitter de = new DebounceEmitter<>(t, idx, this);
-            timer = de;
-            d = worker.schedule(de, timeout, unit);
-            de.setResource(d);
+            if (onDropped != null && currentEmitter != null) {
+                try {
+                    onDropped.accept(timer.value);
+                } catch (Throwable ex) {
+                    Exceptions.throwIfFatal(ex);
+                    upstream.dispose();
+                    downstream.onError(ex);
+                    done = true;
+                }
+            }
+
+            DebounceEmitter newEmitter = new DebounceEmitter<>(t, idx, this);
+            timer = newEmitter;
+            newEmitter.setResource(worker.schedule(newEmitter, timeout, unit));
         }
 
         @Override
@@ -113,15 +128,13 @@ public void onComplete() {
             }
             done = true;
 
-            Disposable d = timer;
+            DebounceEmitter d = timer;
             if (d != null) {
                 d.dispose();
             }
 
-            @SuppressWarnings("unchecked")
-            DebounceEmitter de = (DebounceEmitter)d;
-            if (de != null) {
-                de.run();
+            if (d != null) {
+                d.run();
             }
             downstream.onComplete();
             worker.dispose();
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableDelay.java b/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableDelay.java
index 1801cce1f21..7c01c23f90a 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableDelay.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableDelay.java
@@ -111,7 +111,9 @@ final class OnNext implements Runnable {
 
             @Override
             public void run() {
-                downstream.onNext(t);
+                if (!w.isDisposed()) {
+                    downstream.onNext(t);
+                }
             }
         }
 
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableSampleTimed.java b/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableSampleTimed.java
index f439339e154..f264b8e76d4 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableSampleTimed.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableSampleTimed.java
@@ -18,6 +18,8 @@
 
 import io.reactivex.rxjava3.core.*;
 import io.reactivex.rxjava3.disposables.Disposable;
+import io.reactivex.rxjava3.exceptions.Exceptions;
+import io.reactivex.rxjava3.functions.Consumer;
 import io.reactivex.rxjava3.internal.disposables.DisposableHelper;
 import io.reactivex.rxjava3.observers.SerializedObserver;
 
@@ -25,24 +27,30 @@ public final class ObservableSampleTimed extends AbstractObservableWithUpstre
     final long period;
     final TimeUnit unit;
     final Scheduler scheduler;
-
+    final Consumer onDropped;
     final boolean emitLast;
 
-    public ObservableSampleTimed(ObservableSource source, long period, TimeUnit unit, Scheduler scheduler, boolean emitLast) {
+    public ObservableSampleTimed(ObservableSource source,
+                                 long period,
+                                 TimeUnit unit,
+                                 Scheduler scheduler,
+                                 boolean emitLast,
+                                 Consumer onDropped) {
         super(source);
         this.period = period;
         this.unit = unit;
         this.scheduler = scheduler;
         this.emitLast = emitLast;
+        this.onDropped = onDropped;
     }
 
     @Override
     public void subscribeActual(Observer t) {
         SerializedObserver serial = new SerializedObserver<>(t);
         if (emitLast) {
-            source.subscribe(new SampleTimedEmitLast<>(serial, period, unit, scheduler));
+            source.subscribe(new SampleTimedEmitLast<>(serial, period, unit, scheduler, onDropped));
         } else {
-            source.subscribe(new SampleTimedNoLast<>(serial, period, unit, scheduler));
+            source.subscribe(new SampleTimedNoLast<>(serial, period, unit, scheduler, onDropped));
         }
     }
 
@@ -54,16 +62,18 @@ abstract static class SampleTimedObserver extends AtomicReference implemen
         final long period;
         final TimeUnit unit;
         final Scheduler scheduler;
+        final Consumer onDropped;
 
         final AtomicReference timer = new AtomicReference<>();
 
         Disposable upstream;
 
-        SampleTimedObserver(Observer actual, long period, TimeUnit unit, Scheduler scheduler) {
+        SampleTimedObserver(Observer actual, long period, TimeUnit unit, Scheduler scheduler, Consumer onDropped) {
             this.downstream = actual;
             this.period = period;
             this.unit = unit;
             this.scheduler = scheduler;
+            this.onDropped = onDropped;
         }
 
         @Override
@@ -79,7 +89,17 @@ public void onSubscribe(Disposable d) {
 
         @Override
         public void onNext(T t) {
-            lazySet(t);
+            T oldValue = getAndSet(t);
+            if (oldValue != null && onDropped != null) {
+                try {
+                    onDropped.accept(oldValue);
+                } catch (Throwable throwable) {
+                    Exceptions.throwIfFatal(throwable);
+                    cancelTimer();
+                    upstream.dispose();
+                    downstream.onError(throwable);
+                }
+            }
         }
 
         @Override
@@ -123,8 +143,8 @@ static final class SampleTimedNoLast extends SampleTimedObserver {
 
         private static final long serialVersionUID = -7139995637533111443L;
 
-        SampleTimedNoLast(Observer actual, long period, TimeUnit unit, Scheduler scheduler) {
-            super(actual, period, unit, scheduler);
+        SampleTimedNoLast(Observer actual, long period, TimeUnit unit, Scheduler scheduler, Consumer onDropped) {
+            super(actual, period, unit, scheduler, onDropped);
         }
 
         @Override
@@ -144,8 +164,8 @@ static final class SampleTimedEmitLast extends SampleTimedObserver {
 
         final AtomicInteger wip;
 
-        SampleTimedEmitLast(Observer actual, long period, TimeUnit unit, Scheduler scheduler) {
-            super(actual, period, unit, scheduler);
+        SampleTimedEmitLast(Observer actual, long period, TimeUnit unit, Scheduler scheduler, Consumer onDropped) {
+            super(actual, period, unit, scheduler, onDropped);
             this.wip = new AtomicInteger(1);
         }
 
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableSwitchMap.java b/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableSwitchMap.java
index e213352a050..3e0558aacf1 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableSwitchMap.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableSwitchMap.java
@@ -349,9 +349,10 @@ public void onSubscribe(Disposable d) {
 
         @Override
         public void onNext(R t) {
-            if (index == parent.unique) {
+            SimpleQueue q = queue;
+            if (index == parent.unique && q != null) {
                 if (t != null) {
-                    queue.offer(t);
+                    q.offer(t);
                 }
                 parent.drain();
             }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableThrottleFirstTimed.java b/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableThrottleFirstTimed.java
index 889c203dd7a..6bf3b9f119c 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableThrottleFirstTimed.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableThrottleFirstTimed.java
@@ -19,6 +19,8 @@
 import io.reactivex.rxjava3.core.*;
 import io.reactivex.rxjava3.core.Scheduler.Worker;
 import io.reactivex.rxjava3.disposables.Disposable;
+import io.reactivex.rxjava3.exceptions.Exceptions;
+import io.reactivex.rxjava3.functions.Consumer;
 import io.reactivex.rxjava3.internal.disposables.DisposableHelper;
 import io.reactivex.rxjava3.observers.SerializedObserver;
 
@@ -26,20 +28,27 @@ public final class ObservableThrottleFirstTimed extends AbstractObservableWit
     final long timeout;
     final TimeUnit unit;
     final Scheduler scheduler;
-
-    public ObservableThrottleFirstTimed(ObservableSource source,
-            long timeout, TimeUnit unit, Scheduler scheduler) {
+    final Consumer onDropped;
+
+    public ObservableThrottleFirstTimed(
+            ObservableSource source,
+            long timeout,
+            TimeUnit unit,
+            Scheduler scheduler,
+            Consumer onDropped) {
         super(source);
         this.timeout = timeout;
         this.unit = unit;
         this.scheduler = scheduler;
+        this.onDropped = onDropped;
     }
 
     @Override
     public void subscribeActual(Observer t) {
         source.subscribe(new DebounceTimedObserver<>(
                 new SerializedObserver<>(t),
-                timeout, unit, scheduler.createWorker()));
+                timeout, unit, scheduler.createWorker(),
+                onDropped));
     }
 
     static final class DebounceTimedObserver
@@ -51,16 +60,21 @@ static final class DebounceTimedObserver
         final long timeout;
         final TimeUnit unit;
         final Scheduler.Worker worker;
-
+        final Consumer onDropped;
         Disposable upstream;
-
         volatile boolean gate;
 
-        DebounceTimedObserver(Observer actual, long timeout, TimeUnit unit, Worker worker) {
+        DebounceTimedObserver(
+                Observer actual,
+                long timeout,
+                TimeUnit unit,
+                Worker worker,
+                Consumer onDropped) {
             this.downstream = actual;
             this.timeout = timeout;
             this.unit = unit;
             this.worker = worker;
+            this.onDropped = onDropped;
         }
 
         @Override
@@ -83,6 +97,15 @@ public void onNext(T t) {
                     d.dispose();
                 }
                 DisposableHelper.replace(this, worker.schedule(this, timeout, unit));
+            } else if (onDropped != null) {
+                try {
+                    onDropped.accept(t);
+                } catch (Throwable ex) {
+                    Exceptions.throwIfFatal(ex);
+                    upstream.dispose();
+                    downstream.onError(ex);
+                    worker.dispose();
+                }
             }
         }
 
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableThrottleLatest.java b/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableThrottleLatest.java
index 8f0b2cc2501..caf14d3a5e1 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableThrottleLatest.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/observable/ObservableThrottleLatest.java
@@ -18,7 +18,10 @@
 
 import io.reactivex.rxjava3.core.*;
 import io.reactivex.rxjava3.disposables.Disposable;
+import io.reactivex.rxjava3.exceptions.*;
+import io.reactivex.rxjava3.functions.Consumer;
 import io.reactivex.rxjava3.internal.disposables.DisposableHelper;
+import io.reactivex.rxjava3.plugins.RxJavaPlugins;
 
 /**
  * Emits the next or latest item when the given time elapses.
@@ -41,19 +44,24 @@ public final class ObservableThrottleLatest extends AbstractObservableWithUps
 
     final boolean emitLast;
 
+    final Consumer onDropped;
+
     public ObservableThrottleLatest(Observable source,
-            long timeout, TimeUnit unit, Scheduler scheduler,
-            boolean emitLast) {
+            long timeout, TimeUnit unit,
+            Scheduler scheduler,
+            boolean emitLast,
+            Consumer onDropped) {
         super(source);
         this.timeout = timeout;
         this.unit = unit;
         this.scheduler = scheduler;
         this.emitLast = emitLast;
+        this.onDropped = onDropped;
     }
 
     @Override
     protected void subscribeActual(Observer observer) {
-        source.subscribe(new ThrottleLatestObserver<>(observer, timeout, unit, scheduler.createWorker(), emitLast));
+        source.subscribe(new ThrottleLatestObserver<>(observer, timeout, unit, scheduler.createWorker(), emitLast, onDropped));
     }
 
     static final class ThrottleLatestObserver
@@ -74,6 +82,8 @@ static final class ThrottleLatestObserver
 
         final AtomicReference latest;
 
+        final Consumer onDropped;
+
         Disposable upstream;
 
         volatile boolean done;
@@ -86,14 +96,17 @@ static final class ThrottleLatestObserver
         boolean timerRunning;
 
         ThrottleLatestObserver(Observer downstream,
-                long timeout, TimeUnit unit, Scheduler.Worker worker,
-                boolean emitLast) {
+                long timeout, TimeUnit unit,
+                Scheduler.Worker worker,
+                boolean emitLast,
+                Consumer onDropped) {
             this.downstream = downstream;
             this.timeout = timeout;
             this.unit = unit;
             this.worker = worker;
             this.emitLast = emitLast;
             this.latest = new AtomicReference<>();
+            this.onDropped = onDropped;
         }
 
         @Override
@@ -106,7 +119,17 @@ public void onSubscribe(Disposable d) {
 
         @Override
         public void onNext(T t) {
-            latest.set(t);
+            T old = latest.getAndSet(t);
+            if (onDropped != null && old != null) {
+                try {
+                    onDropped.accept(old);
+                } catch (Throwable ex) {
+                    Exceptions.throwIfFatal(ex);
+                    upstream.dispose();
+                    error = ex;
+                    done = true;
+                }
+            }
             drain();
         }
 
@@ -129,6 +152,22 @@ public void dispose() {
             upstream.dispose();
             worker.dispose();
             if (getAndIncrement() == 0) {
+                clear();
+            }
+        }
+
+        void clear() {
+            if (onDropped != null) {
+                T v = latest.getAndSet(null);
+                if (v != null) {
+                    try {
+                        onDropped.accept(v);
+                    } catch (Throwable ex) {
+                        Exceptions.throwIfFatal(ex);
+                        RxJavaPlugins.onError(ex);
+                    }
+                }
+            } else {
                 latest.lazySet(null);
             }
         }
@@ -158,14 +197,27 @@ void drain() {
 
                 for (;;) {
                     if (cancelled) {
-                        latest.lazySet(null);
+                        clear();
                         return;
                     }
 
                     boolean d = done;
+                    Throwable error = this.error;
 
                     if (d && error != null) {
-                        latest.lazySet(null);
+                        if (onDropped != null) {
+                            T v = latest.getAndSet(null);
+                            if (v != null) {
+                                try {
+                                    onDropped.accept(v);
+                                } catch (Throwable ex) {
+                                    Exceptions.throwIfFatal(ex);
+                                    error = new CompositeException(error, ex);
+                                }
+                            }
+                        } else {
+                            latest.lazySet(null);
+                        }
                         downstream.onError(error);
                         worker.dispose();
                         return;
@@ -175,9 +227,22 @@ void drain() {
                     boolean empty = v == null;
 
                     if (d) {
-                        v = latest.getAndSet(null);
-                        if (!empty && emitLast) {
-                            downstream.onNext(v);
+                        if (!empty) {
+                            v = latest.getAndSet(null);
+                            if (emitLast) {
+                                downstream.onNext(v);
+                            } else {
+                                if (onDropped != null) {
+                                    try {
+                                        onDropped.accept(v);
+                                    } catch (Throwable ex) {
+                                        Exceptions.throwIfFatal(ex);
+                                        downstream.onError(ex);
+                                        worker.dispose();
+                                        return;
+                                    }
+                                }
+                            }
                         }
                         downstream.onComplete();
                         worker.dispose();
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/parallel/ParallelFromPublisher.java b/src/main/java/io/reactivex/rxjava3/internal/operators/parallel/ParallelFromPublisher.java
index 67c2ed48520..eb57bccea5d 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/parallel/ParallelFromPublisher.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/parallel/ParallelFromPublisher.java
@@ -204,7 +204,7 @@ public void onNext(T t) {
             if (sourceMode == QueueSubscription.NONE) {
                 if (!queue.offer(t)) {
                     upstream.cancel();
-                    onError(new MissingBackpressureException("Queue is full?"));
+                    onError(new QueueOverflowException());
                     return;
                 }
             }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/parallel/ParallelJoin.java b/src/main/java/io/reactivex/rxjava3/internal/operators/parallel/ParallelJoin.java
index 3152aaeab8e..2852fda8c7f 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/parallel/ParallelJoin.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/parallel/ParallelJoin.java
@@ -18,7 +18,7 @@
 import org.reactivestreams.*;
 
 import io.reactivex.rxjava3.core.*;
-import io.reactivex.rxjava3.exceptions.MissingBackpressureException;
+import io.reactivex.rxjava3.exceptions.*;
 import io.reactivex.rxjava3.internal.subscriptions.SubscriptionHelper;
 import io.reactivex.rxjava3.internal.util.*;
 import io.reactivex.rxjava3.operators.SimplePlainQueue;
@@ -153,7 +153,7 @@ public void onNext(JoinInnerSubscriber inner, T value) {
 
                     if (!q.offer(value)) {
                         cancelAll();
-                        Throwable mbe = new MissingBackpressureException("Queue full?!");
+                        Throwable mbe = new QueueOverflowException();
                         if (errors.compareAndSet(null, mbe)) {
                             downstream.onError(mbe);
                         } else {
@@ -170,7 +170,7 @@ public void onNext(JoinInnerSubscriber inner, T value) {
 
                 if (!q.offer(value)) {
                     cancelAll();
-                    onError(new MissingBackpressureException("Queue full?!"));
+                    onError(new QueueOverflowException());
                     return;
                 }
 
@@ -333,7 +333,7 @@ void onNext(JoinInnerSubscriber inner, T value) {
 
                     if (!q.offer(value)) {
                         inner.cancel();
-                        errors.tryAddThrowableOrReport(new MissingBackpressureException("Queue full?!"));
+                        errors.tryAddThrowableOrReport(new QueueOverflowException());
                         done.decrementAndGet();
                         drainLoop();
                         return;
@@ -347,7 +347,7 @@ void onNext(JoinInnerSubscriber inner, T value) {
 
                 if (!q.offer(value)) {
                     inner.cancel();
-                    errors.tryAddThrowableOrReport(new MissingBackpressureException("Queue full?!"));
+                    errors.tryAddThrowableOrReport(new QueueOverflowException());
                     done.decrementAndGet();
                 }
 
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/parallel/ParallelRunOn.java b/src/main/java/io/reactivex/rxjava3/internal/operators/parallel/ParallelRunOn.java
index e9c92a0c24c..22f822db34a 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/parallel/ParallelRunOn.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/parallel/ParallelRunOn.java
@@ -19,7 +19,7 @@
 
 import io.reactivex.rxjava3.core.*;
 import io.reactivex.rxjava3.core.Scheduler.Worker;
-import io.reactivex.rxjava3.exceptions.MissingBackpressureException;
+import io.reactivex.rxjava3.exceptions.*;
 import io.reactivex.rxjava3.internal.schedulers.SchedulerMultiWorkerSupport;
 import io.reactivex.rxjava3.internal.schedulers.SchedulerMultiWorkerSupport.WorkerCallback;
 import io.reactivex.rxjava3.internal.subscriptions.SubscriptionHelper;
@@ -148,7 +148,7 @@ public final void onNext(T t) {
             }
             if (!queue.offer(t)) {
                 upstream.cancel();
-                onError(new MissingBackpressureException("Queue is full?!"));
+                onError(new QueueOverflowException());
                 return;
             }
             schedule();
diff --git a/src/main/java/io/reactivex/rxjava3/internal/operators/single/SingleTimeout.java b/src/main/java/io/reactivex/rxjava3/internal/operators/single/SingleTimeout.java
index 609747d1d87..cc5b9237277 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/operators/single/SingleTimeout.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/operators/single/SingleTimeout.java
@@ -113,11 +113,7 @@ public void onError(Throwable e) {
 
         @Override
         public void run() {
-            Disposable d = get();
-            if (d != DisposableHelper.DISPOSED && compareAndSet(d, DisposableHelper.DISPOSED)) {
-                if (d != null) {
-                    d.dispose();
-                }
+            if (DisposableHelper.dispose(this)) {
                 SingleSource other = this.other;
                 if (other == null) {
                     downstream.onError(new TimeoutException(timeoutMessage(timeout, unit)));
diff --git a/src/main/java/io/reactivex/rxjava3/internal/queue/MpscLinkedQueue.java b/src/main/java/io/reactivex/rxjava3/internal/queue/MpscLinkedQueue.java
index d735ff43c07..e8d19c633e3 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/queue/MpscLinkedQueue.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/queue/MpscLinkedQueue.java
@@ -91,6 +91,8 @@ public T poll() {
             // we have to null out the value because we are going to hang on to the node
             final T nextValue = nextNode.getAndNullValue();
             spConsumerNode(nextNode);
+            // unlink previous consumer to help gc
+            currConsumerNode.soNext(null);
             return nextValue;
         }
         else if (currConsumerNode != lvProducerNode()) {
@@ -101,6 +103,8 @@ else if (currConsumerNode != lvProducerNode()) {
             // we have to null out the value because we are going to hang on to the node
             final T nextValue = nextNode.getAndNullValue();
             spConsumerNode(nextNode);
+            // unlink previous consumer to help gc
+            currConsumerNode.soNext(null);
             return nextValue;
         }
         return null;
diff --git a/src/main/java/io/reactivex/rxjava3/internal/schedulers/ExecutorScheduler.java b/src/main/java/io/reactivex/rxjava3/internal/schedulers/ExecutorScheduler.java
index 7c7b0179882..fa0bcab7f86 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/schedulers/ExecutorScheduler.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/schedulers/ExecutorScheduler.java
@@ -204,7 +204,7 @@ public Disposable schedule(@NonNull Runnable run, long delay, @NonNull TimeUnit
 
             final Runnable decoratedRun = RxJavaPlugins.onSchedule(run);
 
-            ScheduledRunnable sr = new ScheduledRunnable(new SequentialDispose(mar, decoratedRun), tasks);
+            ScheduledRunnable sr = new ScheduledRunnable(new SequentialDispose(mar, decoratedRun), tasks, interruptibleWorker);
             tasks.add(sr);
 
             if (executor instanceof ScheduledExecutorService) {
diff --git a/src/main/java/io/reactivex/rxjava3/internal/schedulers/NewThreadWorker.java b/src/main/java/io/reactivex/rxjava3/internal/schedulers/NewThreadWorker.java
index deba4948baa..764241e76e3 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/schedulers/NewThreadWorker.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/schedulers/NewThreadWorker.java
@@ -26,7 +26,7 @@
  * worker but doesn't perform task-tracking operations.
  *
  */
-public class NewThreadWorker extends Scheduler.Worker implements Disposable {
+public class NewThreadWorker extends Scheduler.Worker {
     private final ScheduledExecutorService executor;
 
     volatile boolean disposed;
diff --git a/src/main/java/io/reactivex/rxjava3/internal/schedulers/ScheduledRunnable.java b/src/main/java/io/reactivex/rxjava3/internal/schedulers/ScheduledRunnable.java
index 14c197bccc5..2a1baa641a2 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/schedulers/ScheduledRunnable.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/schedulers/ScheduledRunnable.java
@@ -24,6 +24,7 @@ public final class ScheduledRunnable extends AtomicReferenceArray
 
     private static final long serialVersionUID = -6120223772001106981L;
     final Runnable actual;
+    final boolean interruptOnCancel;
 
     /** Indicates that the parent tracking this task has been notified about its completion. */
     static final Object PARENT_DISPOSED = new Object();
@@ -41,12 +42,26 @@ public final class ScheduledRunnable extends AtomicReferenceArray
     /**
      * Creates a ScheduledRunnable by wrapping the given action and setting
      * up the optional parent.
+     * The underlying future will be interrupted if the task is disposed asynchronously.
      * @param actual the runnable to wrap, not-null (not verified)
      * @param parent the parent tracking container or null if none
      */
     public ScheduledRunnable(Runnable actual, DisposableContainer parent) {
+        this(actual, parent, true);
+    }
+
+    /**
+     * Creates a ScheduledRunnable by wrapping the given action and setting
+     * up the optional parent.
+     * @param actual the runnable to wrap, not-null (not verified)
+     * @param parent the parent tracking container or null if none
+     * @param interruptOnCancel if true, the underlying future will be interrupted when disposing
+     *                          this task from a different thread than it is running on.
+     */
+    public ScheduledRunnable(Runnable actual, DisposableContainer parent, boolean interruptOnCancel) {
         super(3);
         this.actual = actual;
+        this.interruptOnCancel = interruptOnCancel;
         this.lazySet(0, parent);
     }
 
@@ -95,7 +110,7 @@ public void setFuture(Future f) {
                 return;
             }
             if (o == ASYNC_DISPOSED) {
-                f.cancel(true);
+                f.cancel(interruptOnCancel);
                 return;
             }
             if (compareAndSet(FUTURE_INDEX, o, f)) {
@@ -114,7 +129,7 @@ public void dispose() {
             boolean async = get(THREAD_INDEX) != Thread.currentThread();
             if (compareAndSet(FUTURE_INDEX, o, async ? ASYNC_DISPOSED : SYNC_DISPOSED)) {
                 if (o != null) {
-                    ((Future)o).cancel(async);
+                    ((Future)o).cancel(async && interruptOnCancel);
                 }
                 break;
             }
diff --git a/src/main/java/io/reactivex/rxjava3/internal/schedulers/SchedulerWhen.java b/src/main/java/io/reactivex/rxjava3/internal/schedulers/SchedulerWhen.java
index 0780aea6106..814c971f1c6 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/schedulers/SchedulerWhen.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/schedulers/SchedulerWhen.java
@@ -80,7 +80,7 @@
  * }
  * 
  *
- * Slowing down the rate to no more than than 1 a second. This suffers from the
+ * Slowing down the rate to no more than 1 a second. This suffers from the
  * same problem as the one above I could find an {@link Observable} operator
  * that limits the rate without dropping the values (aka leaky bucket
  * algorithm).
diff --git a/src/main/java/io/reactivex/rxjava3/internal/schedulers/TrampolineScheduler.java b/src/main/java/io/reactivex/rxjava3/internal/schedulers/TrampolineScheduler.java
index 7ed777f08f1..04496482b06 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/schedulers/TrampolineScheduler.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/schedulers/TrampolineScheduler.java
@@ -62,7 +62,7 @@ public Disposable scheduleDirect(@NonNull Runnable run, long delay, TimeUnit uni
         return EmptyDisposable.INSTANCE;
     }
 
-    static final class TrampolineWorker extends Scheduler.Worker implements Disposable {
+    static final class TrampolineWorker extends Scheduler.Worker {
         final PriorityBlockingQueue queue = new PriorityBlockingQueue<>();
 
         private final AtomicInteger wip = new AtomicInteger();
diff --git a/src/main/java/io/reactivex/rxjava3/internal/subscribers/QueueDrainSubscriber.java b/src/main/java/io/reactivex/rxjava3/internal/subscribers/QueueDrainSubscriber.java
index 145882e4180..8fb7f552953 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/subscribers/QueueDrainSubscriber.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/subscribers/QueueDrainSubscriber.java
@@ -84,7 +84,7 @@ protected final void fastPathEmitMax(U value, boolean delayError, Disposable dis
                 }
             } else {
                 dispose.dispose();
-                s.onError(new MissingBackpressureException("Could not emit buffer due to lack of requests"));
+                s.onError(MissingBackpressureException.createDefault());
                 return;
             }
         } else {
@@ -118,7 +118,7 @@ protected final void fastPathOrderedEmitMax(U value, boolean delayError, Disposa
             } else {
                 cancelled = true;
                 dispose.dispose();
-                s.onError(new MissingBackpressureException("Could not emit buffer due to lack of requests"));
+                s.onError(MissingBackpressureException.createDefault());
                 return;
             }
         } else {
diff --git a/src/main/java/io/reactivex/rxjava3/internal/util/QueueDrainHelper.java b/src/main/java/io/reactivex/rxjava3/internal/util/QueueDrainHelper.java
index a9a2ab49018..fa0c500892f 100644
--- a/src/main/java/io/reactivex/rxjava3/internal/util/QueueDrainHelper.java
+++ b/src/main/java/io/reactivex/rxjava3/internal/util/QueueDrainHelper.java
@@ -78,7 +78,7 @@ public static  void drainMaxLoop(SimplePlainQueue q, Subscriber
  * Available observer variants
  * 

- * 
+ * 

+ * 
  * 
  * 
  *     
diff --git a/src/main/java/io/reactivex/rxjava3/plugins/RxJavaPlugins.java b/src/main/java/io/reactivex/rxjava3/plugins/RxJavaPlugins.java
index c1115bb478f..2949253b31c 100644
--- a/src/main/java/io/reactivex/rxjava3/plugins/RxJavaPlugins.java
+++ b/src/main/java/io/reactivex/rxjava3/plugins/RxJavaPlugins.java
@@ -402,10 +402,13 @@ static boolean isBug(Throwable error) {
             return true;
         }
         // the sender didn't honor the request amount
-        // it's either due to an operator bug or concurrent onNext
         if (error instanceof MissingBackpressureException) {
             return true;
         }
+        // it's either due to an operator bug or concurrent onNext
+        if (error instanceof QueueOverflowException) {
+            return true;
+        }
         // general protocol violations
         // it's either due to an operator bug or concurrent onNext
         if (error instanceof IllegalStateException) {
diff --git a/src/main/java/io/reactivex/rxjava3/processors/BehaviorProcessor.java b/src/main/java/io/reactivex/rxjava3/processors/BehaviorProcessor.java
index eac40a8a754..2e5117ca560 100644
--- a/src/main/java/io/reactivex/rxjava3/processors/BehaviorProcessor.java
+++ b/src/main/java/io/reactivex/rxjava3/processors/BehaviorProcessor.java
@@ -590,7 +590,7 @@ public boolean test(Object o) {
                 return false;
             }
             cancel();
-            downstream.onError(new MissingBackpressureException("Could not deliver value due to lack of requests"));
+            downstream.onError(MissingBackpressureException.createDefault());
             return true;
         }
 
diff --git a/src/main/java/io/reactivex/rxjava3/processors/MulticastProcessor.java b/src/main/java/io/reactivex/rxjava3/processors/MulticastProcessor.java
index 766e75145d2..14a7a55ee2a 100644
--- a/src/main/java/io/reactivex/rxjava3/processors/MulticastProcessor.java
+++ b/src/main/java/io/reactivex/rxjava3/processors/MulticastProcessor.java
@@ -295,7 +295,7 @@ public void onNext(@NonNull T t) {
             ExceptionHelper.nullCheck(t, "onNext called with a null value.");
             if (!queue.offer(t)) {
                 SubscriptionHelper.cancel(upstream);
-                onError(new MissingBackpressureException());
+                onError(MissingBackpressureException.createDefault());
                 return;
             }
         }
diff --git a/src/main/java/io/reactivex/rxjava3/processors/PublishProcessor.java b/src/main/java/io/reactivex/rxjava3/processors/PublishProcessor.java
index db6787880f0..73507844d20 100644
--- a/src/main/java/io/reactivex/rxjava3/processors/PublishProcessor.java
+++ b/src/main/java/io/reactivex/rxjava3/processors/PublishProcessor.java
@@ -362,7 +362,7 @@ public void onNext(T t) {
                 BackpressureHelper.producedCancel(this, 1);
             } else {
                 cancel();
-                downstream.onError(new MissingBackpressureException("Could not emit value due to lack of requests"));
+                downstream.onError(MissingBackpressureException.createDefault());
             }
         }
 
diff --git a/src/main/java/io/reactivex/rxjava3/schedulers/Schedulers.java b/src/main/java/io/reactivex/rxjava3/schedulers/Schedulers.java
index 112c2559b0b..cb256524048 100644
--- a/src/main/java/io/reactivex/rxjava3/schedulers/Schedulers.java
+++ b/src/main/java/io/reactivex/rxjava3/schedulers/Schedulers.java
@@ -318,7 +318,7 @@ public static Scheduler single() {
      * calls to it.
      * 

      * If the provided executor doesn't support any of the more specific standard Java executor
-     * APIs, cancelling tasks scheduled by this scheduler can't be interrupted when they are
+     * APIs, tasks scheduled by this scheduler can't be interrupted when they are
      * executing but only prevented from running prior to that. In addition, tasks scheduled with
      * a time delay or periodically will use the {@link #single()} scheduler for the timed waiting
      * before posting the actual task to the given executor.
@@ -327,13 +327,13 @@ public static Scheduler single() {
      * {@link #from(Executor, boolean)} overload to enable task interruption via this wrapper.
      * 

      * If the provided executor supports the standard Java {@link ExecutorService} API,
-     * cancelling tasks scheduled by this scheduler can be cancelled/interrupted by calling
+     * tasks scheduled by this scheduler can be cancelled/interrupted by calling
      * {@link io.reactivex.rxjava3.disposables.Disposable#dispose()}. In addition, tasks scheduled with
      * a time delay or periodically will use the {@link #single()} scheduler for the timed waiting
      * before posting the actual task to the given executor.
      * 

      * If the provided executor supports the standard Java {@link ScheduledExecutorService} API,
-     * cancelling tasks scheduled by this scheduler can be cancelled/interrupted by calling
+     * tasks scheduled by this scheduler can be cancelled/interrupted by calling
      * {@link io.reactivex.rxjava3.disposables.Disposable#dispose()}. In addition, tasks scheduled with
      * a time delay or periodically will use the provided executor. Note, however, if the provided
      * {@code ScheduledExecutorService} instance is not single threaded, tasks scheduled
@@ -405,13 +405,13 @@ public static Scheduler from(@NonNull Executor executor) {
      * before posting the actual task to the given executor.
      * 

      * If the provided executor supports the standard Java {@link ExecutorService} API,
-     * canceling tasks scheduled by this scheduler can be cancelled/interrupted by calling
+     * tasks scheduled by this scheduler can be cancelled/interrupted by calling
      * {@link io.reactivex.rxjava3.disposables.Disposable#dispose()}. In addition, tasks scheduled with
      * a time delay or periodically will use the {@link #single()} scheduler for the timed waiting
      * before posting the actual task to the given executor.
      * 

      * If the provided executor supports the standard Java {@link ScheduledExecutorService} API,
-     * canceling tasks scheduled by this scheduler can be cancelled/interrupted by calling
+     * tasks scheduled by this scheduler can be cancelled/interrupted by calling
      * {@link io.reactivex.rxjava3.disposables.Disposable#dispose()}. In addition, tasks scheduled with
      * a time delay or periodically will use the provided executor. Note, however, if the provided
      * {@code ScheduledExecutorService} instance is not single threaded, tasks scheduled
@@ -487,13 +487,13 @@ public static Scheduler from(@NonNull Executor executor, boolean interruptibleWo
      * before posting the actual task to the given executor.
      * 

      * If the provided executor supports the standard Java {@link ExecutorService} API,
-     * canceling tasks scheduled by this scheduler can be cancelled/interrupted by calling
+     * tasks scheduled by this scheduler can be cancelled/interrupted by calling
      * {@link io.reactivex.rxjava3.disposables.Disposable#dispose()}. In addition, tasks scheduled with
      * a time delay or periodically will use the {@link #single()} scheduler for the timed waiting
      * before posting the actual task to the given executor.
      * 

      * If the provided executor supports the standard Java {@link ScheduledExecutorService} API,
-     * canceling tasks scheduled by this scheduler can be cancelled/interrupted by calling
+     * tasks scheduled by this scheduler can be cancelled/interrupted by calling
      * {@link io.reactivex.rxjava3.disposables.Disposable#dispose()}. In addition, tasks scheduled with
      * a time delay or periodically will use the provided executor. Note, however, if the provided
      * {@code ScheduledExecutorService} instance is not single threaded, tasks scheduled
diff --git a/src/main/java/io/reactivex/rxjava3/subjects/BehaviorSubject.java b/src/main/java/io/reactivex/rxjava3/subjects/BehaviorSubject.java
index 465ddcbebcc..2b19ecdd265 100644
--- a/src/main/java/io/reactivex/rxjava3/subjects/BehaviorSubject.java
+++ b/src/main/java/io/reactivex/rxjava3/subjects/BehaviorSubject.java
@@ -59,9 +59,9 @@
  *
  * TestObserver<Integer> to1 = observable.test();
  *
- * observable.onNext(1);
+ * subject.onNext(1);
  * // this will "clear" the cache
- * observable.onNext(EMPTY);
+ * subject.onNext(EMPTY);
  *
  * TestObserver<Integer> to2 = observable.test();
  *
diff --git a/src/main/java/io/reactivex/rxjava3/subjects/ReplaySubject.java b/src/main/java/io/reactivex/rxjava3/subjects/ReplaySubject.java
index 4d5eb3335f2..e103594ba50 100644
--- a/src/main/java/io/reactivex/rxjava3/subjects/ReplaySubject.java
+++ b/src/main/java/io/reactivex/rxjava3/subjects/ReplaySubject.java
@@ -652,8 +652,6 @@ static final class UnboundedReplayBuffer
 
         final List buffer;
 
-        volatile boolean done;
-
         volatile int size;
 
         UnboundedReplayBuffer(int capacityHint) {
@@ -671,7 +669,6 @@ public void addFinal(Object notificationLite) {
             buffer.add(notificationLite);
             trimHead();
             size++;
-            done = true;
         }
 
         @Override
@@ -772,20 +769,17 @@ public void replay(ReplayDisposable rs) {
 
                     Object o = b.get(index);
 
-                    if (done) {
-                        if (index + 1 == s) {
-                            s = size;
-                            if (index + 1 == s) {
-                                if (NotificationLite.isComplete(o)) {
-                                    a.onComplete();
-                                } else {
-                                    a.onError(NotificationLite.getError(o));
-                                }
-                                rs.index = null;
-                                rs.cancelled = true;
-                                return;
-                            }
-                        }
+                    if (NotificationLite.isComplete(o)) {
+                        a.onComplete();
+                        rs.index = null;
+                        rs.cancelled = true;
+                        return;
+                    } else
+                    if (NotificationLite.isError(o)) {
+                        a.onError(NotificationLite.getError(o));
+                        rs.index = null;
+                        rs.cancelled = true;
+                        return;
                     }
 
                     a.onNext((T)o);
@@ -856,8 +850,6 @@ static final class SizeBoundReplayBuffer
 
         Node tail;
 
-        volatile boolean done;
-
         SizeBoundReplayBuffer(int maxSize) {
             this.maxSize = maxSize;
             Node h = new Node<>(null);
@@ -895,7 +887,6 @@ public void addFinal(Object notificationLite) {
             t.lazySet(n); // releases both the tail and size
 
             trimHead();
-            done = true;
         }
 
         /**
@@ -1000,18 +991,17 @@ public void replay(ReplayDisposable rs) {
 
                     Object o = n.value;
 
-                    if (done) {
-                        if (n.get() == null) {
-
-                            if (NotificationLite.isComplete(o)) {
-                                a.onComplete();
-                            } else {
-                                a.onError(NotificationLite.getError(o));
-                            }
-                            rs.index = null;
-                            rs.cancelled = true;
-                            return;
-                        }
+                    if (NotificationLite.isComplete(o)) {
+                        a.onComplete();
+                        rs.index = null;
+                        rs.cancelled = true;
+                        return;
+                    } else
+                    if (NotificationLite.isError(o)) {
+                        a.onError(NotificationLite.getError(o));
+                        rs.index = null;
+                        rs.cancelled = true;
+                        return;
                     }
 
                     a.onNext((T)o);
@@ -1069,8 +1059,6 @@ static final class SizeAndTimeBoundReplayBuffer
 
         TimedNode tail;
 
-        volatile boolean done;
-
         SizeAndTimeBoundReplayBuffer(int maxSize, long maxAge, TimeUnit unit, Scheduler scheduler) {
             this.maxSize = maxSize;
             this.maxAge = maxAge;
@@ -1163,8 +1151,6 @@ public void addFinal(Object notificationLite) {
             size++;
             t.lazySet(n); // releases both the tail and size
             trimFinal();
-
-            done = true;
         }
 
         /**
@@ -1290,18 +1276,17 @@ public void replay(ReplayDisposable rs) {
 
                     Object o = n.value;
 
-                    if (done) {
-                        if (n.get() == null) {
-
-                            if (NotificationLite.isComplete(o)) {
-                                a.onComplete();
-                            } else {
-                                a.onError(NotificationLite.getError(o));
-                            }
-                            rs.index = null;
-                            rs.cancelled = true;
-                            return;
-                        }
+                    if (NotificationLite.isComplete(o)) {
+                        a.onComplete();
+                        rs.index = null;
+                        rs.cancelled = true;
+                        return;
+                    } else
+                    if (NotificationLite.isError(o)) {
+                        a.onError(NotificationLite.getError(o));
+                        rs.index = null;
+                        rs.cancelled = true;
+                        return;
                     }
 
                     a.onNext((T)o);
diff --git a/src/main/java/io/reactivex/rxjava3/subjects/package-info.java b/src/main/java/io/reactivex/rxjava3/subjects/package-info.java
index 60c09e10c06..a2736d7eee5 100644
--- a/src/main/java/io/reactivex/rxjava3/subjects/package-info.java
+++ b/src/main/java/io/reactivex/rxjava3/subjects/package-info.java
@@ -18,7 +18,8 @@
  * 

  * Available subject classes with their respective base classes and consumer interfaces:
  * 

- * 
The available observer types.
Reactive typeBase interfaceSimpleDisposableResource
{@link io.reactivex.rxjava3.core.Observable Observable}

+ * 

+ * 
  * 
  * 
  *     
The available subject classes with their respective base classes and consumer interfaces.
Subject typeBase classConsumer interface
{@link io.reactivex.rxjava3.subjects.Subject Subject}
diff --git a/src/test/java/io/reactivex/rxjava3/disposables/CompositeDisposableTest.java b/src/test/java/io/reactivex/rxjava3/disposables/CompositeDisposableTest.java
index a8ee27b3078..3f76d283d7f 100644
--- a/src/test/java/io/reactivex/rxjava3/disposables/CompositeDisposableTest.java
+++ b/src/test/java/io/reactivex/rxjava3/disposables/CompositeDisposableTest.java
@@ -290,7 +290,7 @@ public void tryRemoveIfNotIn() {
         cd.remove(cd1);
         cd.add(cd2);
 
-        cd.remove(cd1); // try removing agian
+        cd.remove(cd1); // try removing again
     }
 
     @Test(expected = NullPointerException.class)
diff --git a/src/test/java/io/reactivex/rxjava3/exceptions/TestException.java b/src/test/java/io/reactivex/rxjava3/exceptions/TestException.java
index efd568b120c..7bcdd318fd8 100644
--- a/src/test/java/io/reactivex/rxjava3/exceptions/TestException.java
+++ b/src/test/java/io/reactivex/rxjava3/exceptions/TestException.java
@@ -14,7 +14,7 @@
 package io.reactivex.rxjava3.exceptions;
 
 /**
- * Exception for testing if unchecked expections propagate as-is without confusing with
+ * Exception for testing if unchecked exceptions propagate as-is without confusing with
  * other type of common exceptions.
  */
 public final class TestException extends RuntimeException {
diff --git a/src/test/java/io/reactivex/rxjava3/flowable/FlowableBackpressureTests.java b/src/test/java/io/reactivex/rxjava3/flowable/FlowableBackpressureTests.java
index 07ae9c0f270..e6b3a02c684 100644
--- a/src/test/java/io/reactivex/rxjava3/flowable/FlowableBackpressureTests.java
+++ b/src/test/java/io/reactivex/rxjava3/flowable/FlowableBackpressureTests.java
@@ -24,7 +24,7 @@
 import org.reactivestreams.*;
 
 import io.reactivex.rxjava3.core.*;
-import io.reactivex.rxjava3.exceptions.MissingBackpressureException;
+import io.reactivex.rxjava3.exceptions.QueueOverflowException;
 import io.reactivex.rxjava3.functions.*;
 import io.reactivex.rxjava3.internal.subscriptions.SubscriptionHelper;
 import io.reactivex.rxjava3.internal.util.BackpressureHelper;
@@ -132,7 +132,7 @@ public void mergeSync() {
         assertEquals(num, ts.values().size());
         // either one can starve the other, but neither should be capable of doing more than 5 batches (taking 4.1)
         // TODO is it possible to make this deterministic rather than one possibly starving the other?
-        // benjchristensen => In general I'd say it's not worth trying to make it so, as "fair" algoritms generally take a performance hit
+        // benjchristensen => In general I'd say it's not worth trying to make it so, as "fair" algorithms generally take a performance hit
         assertTrue(c1.get() < Flowable.bufferSize() * 5);
         assertTrue(c2.get() < Flowable.bufferSize() * 5);
     }
@@ -154,7 +154,7 @@ public void mergeAsync() {
         assertEquals(num, ts.values().size());
         // either one can starve the other, but neither should be capable of doing more than 5 batches (taking 4.1)
         // TODO is it possible to make this deterministic rather than one possibly starving the other?
-        // benjchristensen => In general I'd say it's not worth trying to make it so, as "fair" algoritms generally take a performance hit
+        // benjchristensen => In general I'd say it's not worth trying to make it so, as "fair" algorithms generally take a performance hit
         int max = Flowable.bufferSize() * 7;
         assertTrue("" + c1.get() + " >= " + max, c1.get() < max);
         assertTrue("" + c2.get() + " >= " + max, c2.get() < max);
@@ -206,7 +206,7 @@ public void mergeAsyncThenObserveOn() {
         assertEquals(num, ts.values().size());
         // either one can starve the other, but neither should be capable of doing more than 5 batches (taking 4.1)
         // TODO is it possible to make this deterministic rather than one possibly starving the other?
-        // benjchristensen => In general I'd say it's not worth trying to make it so, as "fair" algoritms generally take a performance hit
+        // benjchristensen => In general I'd say it's not worth trying to make it so, as "fair" algorithms generally take a performance hit
         // akarnokd => run this in a loop over 10k times and never saw values get as high as 7*SIZE, but since observeOn delays the unsubscription non-deterministically, the test will remain unreliable
         assertTrue(c1.get() < Flowable.bufferSize() * 7);
         assertTrue(c2.get() < Flowable.bufferSize() * 7);
@@ -475,7 +475,7 @@ public Integer apply(Integer v) {
         int vc = ts.values().size();
         assertTrue("10 < " + vc, vc <= 10);
 
-        ts.assertError(MissingBackpressureException.class);
+        ts.assertError(QueueOverflowException.class);
     }
 
     @Test
diff --git a/src/test/java/io/reactivex/rxjava3/flowable/FlowableThrottleLastTests.java b/src/test/java/io/reactivex/rxjava3/flowable/FlowableThrottleLastTests.java
index 0d2dc343fc5..c5c858c4303 100644
--- a/src/test/java/io/reactivex/rxjava3/flowable/FlowableThrottleLastTests.java
+++ b/src/test/java/io/reactivex/rxjava3/flowable/FlowableThrottleLastTests.java
@@ -13,10 +13,14 @@
 
 package io.reactivex.rxjava3.flowable;
 
-import static org.mockito.Mockito.inOrder;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.*;
 
 import java.util.concurrent.TimeUnit;
 
+import io.reactivex.rxjava3.core.Observer;
+import io.reactivex.rxjava3.exceptions.TestException;
+import io.reactivex.rxjava3.functions.Action;
 import org.junit.Test;
 import org.mockito.InOrder;
 import org.reactivestreams.Subscriber;
@@ -28,6 +32,72 @@
 
 public class FlowableThrottleLastTests extends RxJavaTest {
 
+    @Test
+    public void throttleWithDroppedCallbackException() throws Throwable {
+        Subscriber subscriber = TestHelper.mockSubscriber();
+        Action whenDisposed = mock(Action.class);
+
+        TestScheduler s = new TestScheduler();
+        PublishProcessor o = PublishProcessor.create();
+        o.doOnCancel(whenDisposed)
+         .throttleLast(500, TimeUnit.MILLISECONDS, s, e-> {
+                    if (e == 1) {
+                        throw new TestException("forced");
+                    }
+                })
+               .subscribe(subscriber);
+
+        // send events with simulated time increments
+        s.advanceTimeTo(0, TimeUnit.MILLISECONDS);
+        o.onNext(1); // skip
+        o.onNext(2); // deliver
+        s.advanceTimeTo(501, TimeUnit.MILLISECONDS);
+
+        InOrder inOrder = inOrder(subscriber);
+        inOrder.verify(subscriber).onError(any(TestException.class));
+        inOrder.verifyNoMoreInteractions();
+        verify(whenDisposed).run();
+    }
+
+    @Test
+    public void throttleWithDroppedCallback() {
+        Subscriber subscriber = TestHelper.mockSubscriber();
+        Observer dropCallbackObserver = TestHelper.mockObserver();
+
+        TestScheduler s = new TestScheduler();
+        PublishProcessor o = PublishProcessor.create();
+        o.throttleLast(500, TimeUnit.MILLISECONDS, s, dropCallbackObserver::onNext).subscribe(subscriber);
+
+        // send events with simulated time increments
+        s.advanceTimeTo(0, TimeUnit.MILLISECONDS);
+        o.onNext(1); // skip
+        o.onNext(2); // deliver
+        s.advanceTimeTo(501, TimeUnit.MILLISECONDS);
+        o.onNext(3); // skip
+        s.advanceTimeTo(600, TimeUnit.MILLISECONDS);
+        o.onNext(4); // skip
+        s.advanceTimeTo(700, TimeUnit.MILLISECONDS);
+        o.onNext(5); // skip
+        o.onNext(6); // deliver
+        s.advanceTimeTo(1001, TimeUnit.MILLISECONDS);
+        o.onNext(7); // deliver
+        s.advanceTimeTo(1501, TimeUnit.MILLISECONDS);
+        o.onComplete();
+
+        InOrder inOrder = inOrder(subscriber);
+        InOrder dropCallbackOrder = inOrder(dropCallbackObserver);
+        dropCallbackOrder.verify(dropCallbackObserver).onNext(1);
+        inOrder.verify(subscriber).onNext(2);
+        dropCallbackOrder.verify(dropCallbackObserver).onNext(3);
+        dropCallbackOrder.verify(dropCallbackObserver).onNext(4);
+        dropCallbackOrder.verify(dropCallbackObserver).onNext(5);
+        inOrder.verify(subscriber).onNext(6);
+        inOrder.verify(subscriber).onNext(7);
+        inOrder.verify(subscriber).onComplete();
+        inOrder.verifyNoMoreInteractions();
+        dropCallbackOrder.verifyNoMoreInteractions();
+    }
+
     @Test
     public void throttle() {
         Subscriber subscriber = TestHelper.mockSubscriber();
diff --git a/src/test/java/io/reactivex/rxjava3/internal/jdk8/FlowableFlatMapStreamTest.java b/src/test/java/io/reactivex/rxjava3/internal/jdk8/FlowableFlatMapStreamTest.java
index 31e326a3a25..c865d35a526 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/jdk8/FlowableFlatMapStreamTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/jdk8/FlowableFlatMapStreamTest.java
@@ -274,7 +274,7 @@ protected void subscribeActual(Subscriber s) {
             }
             .flatMapStream(v -> Stream.of(1, 2), 1)
             .test(0)
-            .assertFailure(MissingBackpressureException.class);
+            .assertFailure(QueueOverflowException.class);
 
             TestHelper.assertUndeliverable(errors, 0, TestException.class);
         });
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/completable/CompletableConcatTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/completable/CompletableConcatTest.java
index f13cb915582..11bc1a9b064 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/completable/CompletableConcatTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/completable/CompletableConcatTest.java
@@ -52,9 +52,9 @@ public void subscribe(Subscriber s) {
                 }), 1
             )
             .test()
-            .assertFailure(MissingBackpressureException.class);
+            .assertFailure(QueueOverflowException.class);
 
-            TestHelper.assertError(errors, 0, MissingBackpressureException.class);
+            TestHelper.assertError(errors, 0, QueueOverflowException.class);
         } finally {
             RxJavaPlugins.reset();
         }
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/BlockingFlowableToIteratorTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/BlockingFlowableToIteratorTest.java
index a815f738fa1..e5ad7806d36 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/BlockingFlowableToIteratorTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/BlockingFlowableToIteratorTest.java
@@ -152,7 +152,7 @@ public void emptyThrowsNoSuch() {
         it.next();
     }
 
-    @Test(expected = MissingBackpressureException.class)
+    @Test(expected = QueueOverflowException.class)
     public void overflowQueue() {
         Iterator it = new Flowable() {
             @Override
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableAmbTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableAmbTest.java
index ba86c697194..1a1ceca9266 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableAmbTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableAmbTest.java
@@ -402,7 +402,8 @@ public void disposed() {
 
     @Test
     public void manySources() {
-        Flowable[] a = new Flowable[32];
+        @SuppressWarnings("unchecked")
+        Flowable[] a = new Flowable[32];
         Arrays.fill(a, Flowable.never());
         a[31] = Flowable.just(1);
 
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableConcatMapSchedulerTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableConcatMapSchedulerTest.java
index 0f7c7725668..027157ce027 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableConcatMapSchedulerTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableConcatMapSchedulerTest.java
@@ -624,7 +624,7 @@ protected void subscribeActual(Subscriber s) {
         }
         .concatMap(Functions.justFunction(Flowable.just(2)), 8, ImmediateThinScheduler.INSTANCE)
         .test(0L)
-        .assertFailure(IllegalStateException.class);
+        .assertFailure(QueueOverflowException.class);
     }
 
     @Test
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableConcatTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableConcatTest.java
index 986dddad01e..5a0634ffb66 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableConcatTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableConcatTest.java
@@ -1291,7 +1291,7 @@ protected void subscribeActual(Subscriber s) {
         }
         .concatMap(Functions.justFunction(Flowable.just(2)), 8)
         .test(0L)
-        .assertFailure(IllegalStateException.class);
+        .assertFailure(QueueOverflowException.class);
     }
 
     @Test
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableDebounceTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableDebounceTest.java
index 69027d5bd7d..01122106c86 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableDebounceTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableDebounceTest.java
@@ -21,6 +21,7 @@
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicReference;
 
+import io.reactivex.rxjava3.functions.Action;
 import org.junit.*;
 import org.mockito.InOrder;
 import org.reactivestreams.*;
@@ -41,16 +42,86 @@
 public class FlowableDebounceTest extends RxJavaTest {
 
     private TestScheduler scheduler;
-    private Subscriber Subscriber;
+    private Subscriber subscriber;
     private Scheduler.Worker innerScheduler;
 
     @Before
     public void before() {
         scheduler = new TestScheduler();
-        Subscriber = TestHelper.mockSubscriber();
+        subscriber = TestHelper.mockSubscriber();
         innerScheduler = scheduler.createWorker();
     }
 
+    @Test
+    public void debounceWithOnDroppedCallbackWithEx() throws Throwable {
+        Flowable source = Flowable.unsafeCreate(new Publisher() {
+            @Override
+            public void subscribe(Subscriber subscriber) {
+                subscriber.onSubscribe(new BooleanSubscription());
+                publishNext(subscriber, 100, "one");    // Should be skipped since "two" will arrive before the timeout expires.
+                publishNext(subscriber, 400, "two");    // Should be published since "three" will arrive after the timeout expires.
+                publishNext(subscriber, 900, "three");   // Should be skipped since "four" will arrive before the timout expires.
+                publishNext(subscriber, 999, "four");   // Should be skipped since onComplete will arrive before the timeout expires.
+                publishCompleted(subscriber, 1000);     // Should be published as soon as the timeout expires.
+            }
+        });
+
+        Action whenDisposed = mock(Action.class);
+
+        Flowable sampled = source
+                .doOnCancel(whenDisposed)
+                .debounce(400, TimeUnit.MILLISECONDS, scheduler, e ->  {
+                    if ("three".equals(e)) {
+                        throw new TestException("forced");
+                    }
+                });
+        sampled.subscribe(subscriber);
+
+        InOrder inOrder = inOrder(subscriber);
+
+        scheduler.advanceTimeTo(1000, TimeUnit.MILLISECONDS);
+        inOrder.verify(subscriber, times(1)).onNext("two");
+        inOrder.verify(subscriber, times(1)).onError(any(TestException.class));
+        inOrder.verify(subscriber, times(0)).onNext("three");
+        inOrder.verify(subscriber, times(0)).onNext("four");
+        inOrder.verify(subscriber, times(0)).onComplete();
+        inOrder.verifyNoMoreInteractions();
+        verify(whenDisposed).run();
+    }
+
+    @Test
+    public void debounceWithOnDroppedCallback() {
+        Flowable source = Flowable.unsafeCreate(new Publisher() {
+            @Override
+            public void subscribe(Subscriber subscriber) {
+                subscriber.onSubscribe(new BooleanSubscription());
+                publishNext(subscriber, 100, "one");    // Should be skipped since "two" will arrive before the timeout expires.
+                publishNext(subscriber, 400, "two");    // Should be published since "three" will arrive after the timeout expires.
+                publishNext(subscriber, 900, "three");   // Should be skipped since "four" will arrive before the timout expires.
+                publishNext(subscriber, 999, "four");   // Should be skipped since onComplete will arrive before the timeout expires.
+                publishCompleted(subscriber, 1000);     // Should be published as soon as the timeout expires.
+            }
+        });
+
+        Observer dropCallbackObserver = TestHelper.mockObserver();
+        Flowable sampled = source.debounce(400, TimeUnit.MILLISECONDS, scheduler, dropCallbackObserver::onNext);
+        sampled.subscribe(subscriber);
+
+        scheduler.advanceTimeTo(0, TimeUnit.MILLISECONDS);
+        InOrder inOrder = inOrder(subscriber);
+        InOrder dropCallbackOrder = inOrder(dropCallbackObserver);
+
+        // must go to 800 since it must be 400 after when two is sent, which is at 400
+        scheduler.advanceTimeTo(800, TimeUnit.MILLISECONDS);
+        inOrder.verify(subscriber, times(1)).onNext("two");
+        dropCallbackOrder.verify(dropCallbackObserver, times(1)).onNext("one");
+        scheduler.advanceTimeTo(1000, TimeUnit.MILLISECONDS);
+        dropCallbackOrder.verify(dropCallbackObserver, times(1)).onNext("three");
+        inOrder.verify(subscriber, times(1)).onComplete();
+        inOrder.verifyNoMoreInteractions();
+        dropCallbackOrder.verifyNoMoreInteractions();
+    }
+
     @Test
     public void debounceWithCompleted() {
         Flowable source = Flowable.unsafeCreate(new Publisher() {
@@ -65,15 +136,15 @@ public void subscribe(Subscriber subscriber) {
         });
 
         Flowable sampled = source.debounce(400, TimeUnit.MILLISECONDS, scheduler);
-        sampled.subscribe(Subscriber);
+        sampled.subscribe(subscriber);
 
         scheduler.advanceTimeTo(0, TimeUnit.MILLISECONDS);
-        InOrder inOrder = inOrder(Subscriber);
+        InOrder inOrder = inOrder(subscriber);
         // must go to 800 since it must be 400 after when two is sent, which is at 400
         scheduler.advanceTimeTo(800, TimeUnit.MILLISECONDS);
-        inOrder.verify(Subscriber, times(1)).onNext("two");
+        inOrder.verify(subscriber, times(1)).onNext("two");
         scheduler.advanceTimeTo(1000, TimeUnit.MILLISECONDS);
-        inOrder.verify(Subscriber, times(1)).onComplete();
+        inOrder.verify(subscriber, times(1)).onComplete();
         inOrder.verifyNoMoreInteractions();
     }
 
@@ -97,13 +168,13 @@ public void subscribe(Subscriber subscriber) {
         });
 
         Flowable sampled = source.debounce(200, TimeUnit.MILLISECONDS, scheduler);
-        sampled.subscribe(Subscriber);
+        sampled.subscribe(subscriber);
 
         scheduler.advanceTimeTo(0, TimeUnit.MILLISECONDS);
-        InOrder inOrder = inOrder(Subscriber);
-        inOrder.verify(Subscriber, times(0)).onNext(anyString());
+        InOrder inOrder = inOrder(subscriber);
+        inOrder.verify(subscriber, times(0)).onNext(anyString());
         scheduler.advanceTimeTo(1000, TimeUnit.MILLISECONDS);
-        inOrder.verify(Subscriber, times(1)).onComplete();
+        inOrder.verify(subscriber, times(1)).onComplete();
         inOrder.verifyNoMoreInteractions();
     }
 
@@ -121,15 +192,15 @@ public void subscribe(Subscriber subscriber) {
         });
 
         Flowable sampled = source.debounce(400, TimeUnit.MILLISECONDS, scheduler);
-        sampled.subscribe(Subscriber);
+        sampled.subscribe(subscriber);
 
         scheduler.advanceTimeTo(0, TimeUnit.MILLISECONDS);
-        InOrder inOrder = inOrder(Subscriber);
+        InOrder inOrder = inOrder(subscriber);
         // 100 + 400 means it triggers at 500
         scheduler.advanceTimeTo(500, TimeUnit.MILLISECONDS);
-        inOrder.verify(Subscriber).onNext("one");
+        inOrder.verify(subscriber).onNext("one");
         scheduler.advanceTimeTo(701, TimeUnit.MILLISECONDS);
-        inOrder.verify(Subscriber).onError(any(TestException.class));
+        inOrder.verify(subscriber).onError(any(TestException.class));
         inOrder.verifyNoMoreInteractions();
     }
 
@@ -530,7 +601,7 @@ public void timedBadRequest() {
     public void timedLateEmit() {
         TestSubscriber ts = new TestSubscriber<>();
         DebounceTimedSubscriber sub = new DebounceTimedSubscriber<>(
-                ts, 1, TimeUnit.SECONDS, new TestScheduler().createWorker());
+                ts, 1, TimeUnit.SECONDS, new TestScheduler().createWorker(), null);
 
         sub.onSubscribe(new BooleanSubscription());
 
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableDelayTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableDelayTest.java
index 3160f61173e..4d67594a177 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableDelayTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableDelayTest.java
@@ -20,6 +20,7 @@
 import java.util.*;
 import java.util.concurrent.*;
 import java.util.concurrent.atomic.*;
+import java.util.concurrent.locks.LockSupport;
 
 import org.junit.*;
 import org.mockito.InOrder;
@@ -28,6 +29,7 @@
 import io.reactivex.rxjava3.core.*;
 import io.reactivex.rxjava3.exceptions.TestException;
 import io.reactivex.rxjava3.functions.*;
+import io.reactivex.rxjava3.internal.disposables.SequentialDisposable;
 import io.reactivex.rxjava3.internal.functions.Functions;
 import io.reactivex.rxjava3.processors.PublishProcessor;
 import io.reactivex.rxjava3.schedulers.*;
@@ -1030,4 +1032,38 @@ public Publisher apply(Integer t) throws Exception {
         .to(TestHelper.testConsumer())
         .assertFailureAndMessage(NullPointerException.class, "The itemDelay returned a null Publisher");
     }
+
+    @Test
+    public void cancelShouldPreventRandomSubsequentEmissions() {
+        for (int attempt = 1; attempt < 100; attempt ++) {
+
+            SequentialDisposable disposable = new SequentialDisposable();
+            ConcurrentLinkedQueue sink = new ConcurrentLinkedQueue<>();
+
+            disposable.replace(
+                Flowable.range(1, 10)
+                .delay(1, TimeUnit.MICROSECONDS, Schedulers.computation(), true)
+                .doOnNext(v -> {
+                    if (v == 1) {
+                        Schedulers.computation().scheduleDirect(disposable::dispose);
+                    }
+                    sink.offer(v);
+                })
+            .subscribe());
+
+            LockSupport.parkNanos(TimeUnit.MILLISECONDS.toNanos(1));
+
+            Integer last = null;
+
+            while (!sink.isEmpty()) {
+                Integer current = sink.poll();
+
+                if (last != null && last + 1 != current) {
+                    fail("Emission hole: " + last + " -> " + current);
+                }
+
+                last = current;
+            }
+        }
+    }
 }
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableFlatMapTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableFlatMapTest.java
index b7f574b7256..be94c5e57c7 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableFlatMapTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableFlatMapTest.java
@@ -1391,7 +1391,7 @@ protected void subscribeActual(@NonNull Subscriber<@NonNull ? super @NonNull Int
         }
         .flatMap(v -> Flowable.just(v), 1)
         .test(0L)
-        .assertFailure(MissingBackpressureException.class);
+        .assertFailure(QueueOverflowException.class);
     }
 
     @Test
@@ -1413,7 +1413,7 @@ protected void subscribeActual(@NonNull Subscriber<@NonNull ? super @NonNull Int
             }
         })
         .test()
-        .assertFailure(MissingBackpressureException.class, 1);
+        .assertFailure(QueueOverflowException.class, 1);
     }
 
     @Test
@@ -1430,7 +1430,7 @@ protected void subscribeActual(@NonNull Subscriber<@NonNull ? super @NonNull Int
             }
         }, false, 1, 1)
         .test(0L)
-        .assertFailure(MissingBackpressureException.class);
+        .assertFailure(QueueOverflowException.class);
     }
 
     @Test
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableFlattenIterableTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableFlattenIterableTest.java
index 27e4ca128d1..2cb9392e19c 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableFlattenIterableTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableFlattenIterableTest.java
@@ -814,7 +814,7 @@ protected void subscribeActual(Subscriber s) {
         }
         .flatMapIterable(Functions.justFunction(Arrays.asList(1)), 1)
         .test(0L)
-        .assertFailure(MissingBackpressureException.class);
+        .assertFailure(QueueOverflowException.class);
     }
 
     @Test
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableFromSourceTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableFromSourceTest.java
index 03275dd2e93..6506c010ea9 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableFromSourceTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableFromSourceTest.java
@@ -137,7 +137,7 @@ public void normalError() {
         ts.assertError(MissingBackpressureException.class);
         ts.assertNotComplete();
 
-        Assert.assertEquals("create: could not emit value due to lack of requests", ts.errors().get(0).getMessage());
+        Assert.assertEquals("create: " + MissingBackpressureException.DEFAULT_MESSAGE, ts.errors().get(0).getMessage());
     }
 
     @Test
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableObserveOnTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableObserveOnTest.java
index a4839b46163..e4e3d6f3fe8 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableObserveOnTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableObserveOnTest.java
@@ -579,13 +579,13 @@ public void onNext(Integer t) {
         assertEquals(1, errors.size());
         System.out.println("Errors: " + errors);
         Throwable t = errors.get(0);
-        if (t instanceof MissingBackpressureException) {
+        if (t instanceof QueueOverflowException) {
             // success, we expect this
         } else {
-            if (t.getCause() instanceof MissingBackpressureException) {
+            if (t.getCause() instanceof QueueOverflowException) {
                 // this is also okay
             } else {
-                fail("Expecting MissingBackpressureException");
+                fail("Expecting QueueOverflowException");
             }
         }
     }
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureBufferStrategyTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureBufferStrategyTest.java
index 4fc8ba3c251..217162c206c 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureBufferStrategyTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureBufferStrategyTest.java
@@ -15,7 +15,9 @@
 
 import static io.reactivex.rxjava3.core.BackpressureOverflowStrategy.*;
 import static io.reactivex.rxjava3.internal.functions.Functions.EMPTY_ACTION;
-import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.*;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.*;
 
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
@@ -28,8 +30,9 @@
 import io.reactivex.rxjava3.functions.*;
 import io.reactivex.rxjava3.internal.functions.Functions;
 import io.reactivex.rxjava3.internal.subscriptions.BooleanSubscription;
+import io.reactivex.rxjava3.processors.PublishProcessor;
 import io.reactivex.rxjava3.subscribers.*;
-import io.reactivex.rxjava3.testsupport.TestHelper;
+import io.reactivex.rxjava3.testsupport.*;
 
 public class FlowableOnBackpressureBufferStrategyTest extends RxJavaTest {
 
@@ -225,4 +228,98 @@ public void cancelOnDrain() {
         .requestMore(10)
         .assertResult(1);
     }
+
+    @Test
+    public void onDroppedNormalDropOldest() throws Throwable {
+        PublishProcessor pp = PublishProcessor.create();
+
+        @SuppressWarnings("unchecked")
+        Consumer onDropped = mock(Consumer.class);
+
+        TestSubscriber ts = pp.onBackpressureBuffer(1, null, BackpressureOverflowStrategy.DROP_OLDEST, onDropped)
+        .test(0L);
+
+        ts.assertEmpty();
+
+        pp.onNext(1);
+
+        ts.assertEmpty();
+        verify(onDropped, never()).accept(any());
+
+        pp.onNext(2);
+
+        ts.assertEmpty();
+
+        verify(onDropped).accept(1);
+    }
+
+    @Test
+    public void onDroppedNormalDropLatest() throws Throwable {
+        PublishProcessor pp = PublishProcessor.create();
+
+        @SuppressWarnings("unchecked")
+        Consumer onDropped = mock(Consumer.class);
+
+        TestSubscriber ts = pp.onBackpressureBuffer(2, null, BackpressureOverflowStrategy.DROP_LATEST, onDropped)
+        .test(0L);
+
+        ts.assertEmpty();
+
+        pp.onNext(1);
+
+        pp.onNext(2);
+
+        ts.assertEmpty();
+        verify(onDropped, never()).accept(any());
+
+        pp.onNext(3);
+
+        ts.assertEmpty();
+
+        verify(onDropped).accept(2);
+    }
+
+    @Test
+    public void onDroppedNormalError() throws Throwable {
+        PublishProcessor pp = PublishProcessor.create();
+
+        @SuppressWarnings("unchecked")
+        Consumer onDropped = mock(Consumer.class);
+
+        TestSubscriber ts = pp.onBackpressureBuffer(1, null, BackpressureOverflowStrategy.ERROR, onDropped)
+        .test(0L);
+
+        ts.assertEmpty();
+
+        pp.onNext(1);
+
+        ts.assertEmpty();
+        verify(onDropped, never()).accept(any());
+
+        pp.onNext(2);
+
+        ts.assertFailure(MissingBackpressureException.class);
+
+        verify(onDropped).accept(2);
+    }
+
+    @Test
+    public void onDroppedCrash() throws Throwable {
+        PublishProcessor pp = PublishProcessor.create();
+
+        Consumer onDropped = v -> { throw new TestException(); };
+
+        TestSubscriberEx ts = pp.onBackpressureBuffer(1, null, BackpressureOverflowStrategy.DROP_OLDEST, onDropped)
+        .subscribeWith(new TestSubscriberEx(0L));
+
+        ts.assertEmpty();
+
+        pp.onNext(1);
+
+        ts.assertEmpty();
+
+        pp.onNext(2);
+
+        ts.assertFailure(TestException.class);
+    }
 }
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureBufferTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureBufferTest.java
index 5a02218423b..657ce36f1b3 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureBufferTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureBufferTest.java
@@ -14,6 +14,8 @@
 package io.reactivex.rxjava3.internal.operators.flowable;
 
 import static org.junit.Assert.*;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.*;
 
 import java.util.List;
 import java.util.concurrent.*;
@@ -350,4 +352,50 @@ public void doubleOnSubscribe() {
     public void badRequest() {
         TestHelper.assertBadRequestReported(Flowable.never().onBackpressureBuffer());
     }
+
+    @Test
+    public void onDroppedNormal() throws Throwable {
+        PublishProcessor pp = PublishProcessor.create();
+
+        @SuppressWarnings("unchecked")
+        Consumer onDropped = mock(Consumer.class);
+
+        TestSubscriber ts = pp.onBackpressureBuffer(1, false, false, () -> { }, onDropped)
+                .test(0L);
+
+        ts.assertEmpty();
+
+        pp.onNext(1);
+
+        ts.assertEmpty();
+        verify(onDropped, never()).accept(any());
+
+        pp.onNext(2);
+
+        ts.assertFailure(MissingBackpressureException.class);
+
+        verify(onDropped).accept(2);
+    }
+
+    @Test
+    public void onDroppedCrash() throws Throwable {
+        PublishProcessor pp = PublishProcessor.create();
+
+        Consumer onDropped = v -> { throw new TestException(); };
+
+        TestSubscriberEx ts = pp.onBackpressureBuffer(1, false, false, () -> { }, onDropped)
+        .subscribeWith(new TestSubscriberEx(0L));
+
+        ts.assertEmpty();
+
+        pp.onNext(1);
+
+        ts.assertEmpty();
+
+        pp.onNext(2);
+
+        ts.assertFailure(MissingBackpressureException.class);
+
+        assertTrue(ts.errors().get(0).getCause() instanceof TestException);
+    }
 }
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureLatestTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureLatestTest.java
index eb4cfaf2882..f0d50994ed7 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureLatestTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableOnBackpressureLatestTest.java
@@ -17,6 +17,7 @@
 import java.util.concurrent.TimeUnit;
 
 import org.junit.*;
+import org.mockito.InOrder;
 import org.reactivestreams.Publisher;
 
 import io.reactivex.rxjava3.core.*;
@@ -27,6 +28,8 @@
 import io.reactivex.rxjava3.subscribers.TestSubscriber;
 import io.reactivex.rxjava3.testsupport.*;
 
+import static org.mockito.Mockito.inOrder;
+
 public class FlowableOnBackpressureLatestTest extends RxJavaTest {
     @Test
     public void simple() {
@@ -62,6 +65,68 @@ public void simpleBackpressure() {
         ts.assertNotComplete();
     }
 
+    @Test
+    public void simpleBackpressureWithOnDroppedCallback() {
+        PublishProcessor source = PublishProcessor.create();
+        TestSubscriberEx ts = new TestSubscriberEx<>(0L);
+
+        Observer dropCallbackObserver = TestHelper.mockObserver();
+
+        source.onBackpressureLatest(dropCallbackObserver::onNext)
+                .subscribe(ts);
+
+        ts.assertNoValues();
+
+        source.onNext(1);
+        source.onNext(2);
+        source.onNext(3);
+
+        ts.request(1);
+
+        ts.assertValues(3);
+
+        source.onNext(4);
+        source.onNext(5);
+
+        ts.request(2);
+
+        ts.assertValues(3,5);
+
+        InOrder dropCallbackOrder = inOrder(dropCallbackObserver);
+        dropCallbackOrder.verify(dropCallbackObserver).onNext(1);
+        dropCallbackOrder.verify(dropCallbackObserver).onNext(2);
+        dropCallbackOrder.verify(dropCallbackObserver).onNext(4);
+        dropCallbackOrder.verifyNoMoreInteractions();
+    }
+
+    @Test
+    public void simpleBackpressureWithOnDroppedCallbackEx() {
+        PublishProcessor source = PublishProcessor.create();
+        TestSubscriberEx ts = new TestSubscriberEx<>(0L);
+
+        source.onBackpressureLatest(e -> {
+                    if (e == 3) {
+                        throw new TestException("forced");
+                    }
+                })
+                .subscribe(ts);
+
+        ts.assertNoValues();
+
+        source.onNext(1);
+        source.onNext(2);
+
+        ts.request(1);
+
+        ts.assertValues(2);
+
+        source.onNext(3);
+        source.onNext(4);
+
+        ts.assertError(TestException.class);
+        ts.assertValues(2);
+    }
+
     @Test
     public void synchronousDrop() {
         PublishProcessor source = PublishProcessor.create();
@@ -105,7 +170,7 @@ public void synchronousDrop() {
     }
 
     @Test
-    public void asynchronousDrop() throws InterruptedException {
+    public void asynchronousDrop() {
         TestSubscriberEx ts = new TestSubscriberEx(1L) {
             final Random rnd = new Random();
             @Override
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowablePublishFunctionTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowablePublishFunctionTest.java
index e27d5dffcd3..5511fd0123c 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowablePublishFunctionTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowablePublishFunctionTest.java
@@ -189,7 +189,7 @@ public void overflowMissingBackpressureException() {
         ts.assertError(MissingBackpressureException.class);
         ts.assertNotComplete();
 
-        Assert.assertEquals("Could not emit value due to lack of requests",
+        Assert.assertEquals(MissingBackpressureException.DEFAULT_MESSAGE,
                 ts.errors().get(0).getMessage());
         Assert.assertFalse("Source has subscribers?", pp.hasSubscribers());
     }
@@ -212,7 +212,7 @@ public void overflowMissingBackpressureExceptionDelayed() {
         ts.assertError(MissingBackpressureException.class);
         ts.assertNotComplete();
 
-        Assert.assertEquals("Could not emit value due to lack of requests", ts.errors().get(0).getMessage());
+        Assert.assertEquals(MissingBackpressureException.DEFAULT_MESSAGE, ts.errors().get(0).getMessage());
         Assert.assertFalse("Source has subscribers?", pp.hasSubscribers());
     }
 
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowablePublishTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowablePublishTest.java
index ab94d5b2e6b..c3355e9a38f 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowablePublishTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowablePublishTest.java
@@ -905,9 +905,9 @@ public void subscribe(FlowableEmitter s) throws Exception {
             .test(0L)
             // 3.x emits errors last, even the full queue errors
             .requestMore(10)
-            .assertFailure(MissingBackpressureException.class, 0, 1, 2, 3, 4, 5, 6, 7);
+            .assertFailure(QueueOverflowException.class, 0, 1, 2, 3, 4, 5, 6, 7);
 
-            TestHelper.assertError(errors, 0, MissingBackpressureException.class);
+            TestHelper.assertError(errors, 0, QueueOverflowException.class);
         } finally {
             RxJavaPlugins.reset();
         }
@@ -1596,7 +1596,7 @@ protected void subscribeActual(Subscriber s) {
         .refCount()
         .test(0)
         .requestMore(1)
-        .assertFailure(MissingBackpressureException.class, 1);
+        .assertFailure(QueueOverflowException.class, 1);
     }
 
     @Test
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableSwitchTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableSwitchTest.java
index 9d3d16872ea..9f200e3c566 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableSwitchTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableSwitchTest.java
@@ -1076,7 +1076,7 @@ protected void subscribeActual(Subscriber s) {
             }
         }), 8)
         .test(1L)
-        .assertFailure(MissingBackpressureException.class, 0);
+        .assertFailure(QueueOverflowException.class, 0);
     }
 
     @Test
@@ -1377,4 +1377,19 @@ Flowable createFlowable(AtomicInteger inner) {
             inner.incrementAndGet();
         });
     }
+
+    @Test
+    public void innerOnSubscribeOuterCancelRace() {
+        TestSubscriber ts = new TestSubscriber();
+
+        Flowable.just(1)
+        .hide()
+        .switchMap(v -> Flowable.just(1)
+                .doOnSubscribe(d -> ts.cancel())
+                .scan(1, (a, b) -> a)
+        )
+        .subscribe(ts);
+
+        ts.assertEmpty();
+    }
 }
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableThrottleFirstTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableThrottleFirstTest.java
index 9b71893c636..68a559e3cdc 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableThrottleFirstTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableThrottleFirstTest.java
@@ -19,6 +19,7 @@
 import java.util.List;
 import java.util.concurrent.TimeUnit;
 
+import io.reactivex.rxjava3.functions.Action;
 import org.junit.*;
 import org.mockito.InOrder;
 import org.reactivestreams.*;
@@ -44,6 +45,77 @@ public void before() {
         subscriber = TestHelper.mockSubscriber();
     }
 
+    @Test
+    public void throttlingWithDropCallbackCrashes() throws Throwable {
+        Flowable source = Flowable.unsafeCreate(new Publisher() {
+            @Override
+            public void subscribe(Subscriber subscriber) {
+                subscriber.onSubscribe(new BooleanSubscription());
+                publishNext(subscriber, 100, "one");    // publish as it's first
+                publishNext(subscriber, 300, "two");    // skip as it's last within the first 400
+                publishNext(subscriber, 900, "three");   // publish
+                publishNext(subscriber, 905, "four");   // skip
+                publishCompleted(subscriber, 1000);     // Should be published as soon as the timeout expires.
+            }
+        });
+
+        Action whenDisposed = mock(Action.class);
+
+        Flowable sampled = source
+                .doOnCancel(whenDisposed)
+                .throttleFirst(400, TimeUnit.MILLISECONDS, scheduler, e ->  {
+            if ("two".equals(e)) {
+                throw new TestException("forced");
+            }
+        });
+        sampled.subscribe(subscriber);
+
+        InOrder inOrder = inOrder(subscriber);
+
+        scheduler.advanceTimeTo(1000, TimeUnit.MILLISECONDS);
+        inOrder.verify(subscriber, times(1)).onNext("one");
+        inOrder.verify(subscriber, times(1)).onError(any(TestException.class));
+        inOrder.verify(subscriber, times(0)).onNext("two");
+        inOrder.verify(subscriber, times(0)).onNext("three");
+        inOrder.verify(subscriber, times(0)).onNext("four");
+        inOrder.verify(subscriber, times(0)).onComplete();
+        inOrder.verifyNoMoreInteractions();
+        verify(whenDisposed).run();
+    }
+
+    @Test
+    public void throttlingWithDropCallback() {
+        Flowable source = Flowable.unsafeCreate(new Publisher() {
+            @Override
+            public void subscribe(Subscriber subscriber) {
+                subscriber.onSubscribe(new BooleanSubscription());
+                publishNext(subscriber, 100, "one");    // publish as it's first
+                publishNext(subscriber, 300, "two");    // skip as it's last within the first 400
+                publishNext(subscriber, 900, "three");   // publish
+                publishNext(subscriber, 905, "four");   // skip
+                publishCompleted(subscriber, 1000);     // Should be published as soon as the timeout expires.
+            }
+        });
+
+        Observer dropCallbackObserver = TestHelper.mockObserver();
+        Flowable sampled = source.throttleFirst(400, TimeUnit.MILLISECONDS, scheduler, dropCallbackObserver::onNext);
+        sampled.subscribe(subscriber);
+
+        InOrder inOrder = inOrder(subscriber);
+        InOrder dropCallbackOrder = inOrder(dropCallbackObserver);
+
+        scheduler.advanceTimeTo(1000, TimeUnit.MILLISECONDS);
+        inOrder.verify(subscriber, times(1)).onNext("one");
+        inOrder.verify(subscriber, times(0)).onNext("two");
+        dropCallbackOrder.verify(dropCallbackObserver, times(1)).onNext("two");
+        inOrder.verify(subscriber, times(1)).onNext("three");
+        inOrder.verify(subscriber, times(0)).onNext("four");
+        dropCallbackOrder.verify(dropCallbackObserver, times(1)).onNext("four");
+        inOrder.verify(subscriber, times(1)).onComplete();
+        inOrder.verifyNoMoreInteractions();
+        dropCallbackOrder.verifyNoMoreInteractions();
+    }
+
     @Test
     public void throttlingWithCompleted() {
         Flowable source = Flowable.unsafeCreate(new Publisher() {
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableThrottleLatestTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableThrottleLatestTest.java
index fe19765b208..2b26ec98d41 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableThrottleLatestTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableThrottleLatestTest.java
@@ -23,10 +23,11 @@
 import io.reactivex.rxjava3.core.*;
 import io.reactivex.rxjava3.exceptions.*;
 import io.reactivex.rxjava3.functions.*;
+import io.reactivex.rxjava3.internal.subscriptions.EmptySubscription;
 import io.reactivex.rxjava3.processors.PublishProcessor;
 import io.reactivex.rxjava3.schedulers.TestScheduler;
 import io.reactivex.rxjava3.subscribers.TestSubscriber;
-import io.reactivex.rxjava3.testsupport.TestHelper;
+import io.reactivex.rxjava3.testsupport.*;
 
 public class FlowableThrottleLatestTest extends RxJavaTest {
 
@@ -278,4 +279,480 @@ public void onNext(Integer t) {
 
         ts.assertResult(1, 2);
     }
+
+    /** Emit 1, 2, 3, then advance time by a second; 1 and 3 should end up in downstream, 2 should be dropped. */
+    @Test
+    public void onDroppedBasicNoEmitLast() {
+        PublishProcessor pp =PublishProcessor.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        TestSubscriber drops = new TestSubscriber<>();
+        drops.onSubscribe(EmptySubscription.INSTANCE);
+
+        TestSubscriber ts = pp.throttleLatest(1, TimeUnit.SECONDS, sch, false, drops::onNext)
+        .test();
+
+        ts.assertEmpty();
+        drops.assertEmpty();
+
+        pp.onNext(1);
+
+        ts.assertValuesOnly(1);
+        drops.assertEmpty();
+
+        pp.onNext(2);
+
+        ts.assertValuesOnly(1);
+        drops.assertEmpty();
+
+        pp.onNext(3);
+
+        ts.assertValuesOnly(1);
+        drops.assertValuesOnly(2);
+
+        sch.advanceTimeBy(1, TimeUnit.SECONDS);
+
+        ts.assertValuesOnly(1, 3);
+        drops.assertValuesOnly(2);
+
+        pp.onComplete();
+
+        ts.assertResult(1, 3);
+
+        drops.assertValuesOnly(2);
+    }
+
+    /** Emit 1, 2, 3; 1 should end up in downstream, 2, 3 should be dropped. */
+    @Test
+    public void onDroppedBasicNoEmitLastDropLast() {
+        PublishProcessor pp =PublishProcessor.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        TestSubscriber drops = new TestSubscriber<>();
+        drops.onSubscribe(EmptySubscription.INSTANCE);
+
+        TestSubscriber ts = pp.throttleLatest(1, TimeUnit.SECONDS, sch, false, drops::onNext)
+        .test();
+
+        ts.assertEmpty();
+        drops.assertEmpty();
+
+        pp.onNext(1);
+
+        ts.assertValuesOnly(1);
+        drops.assertEmpty();
+
+        pp.onNext(2);
+
+        ts.assertValuesOnly(1);
+        drops.assertEmpty();
+
+        pp.onNext(3);
+
+        ts.assertValuesOnly(1);
+        drops.assertValuesOnly(2);
+
+        pp.onComplete();
+
+        ts.assertResult(1);
+
+        drops.assertValuesOnly(2, 3);
+    }
+
+    /** Emit 1, 2, 3; 1 and 3 should end up in downstream, 2 should be dropped. */
+    @Test
+    public void onDroppedBasicEmitLast() {
+        PublishProcessor pp =PublishProcessor.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        TestSubscriber drops = new TestSubscriber<>();
+        drops.onSubscribe(EmptySubscription.INSTANCE);
+
+        TestSubscriber ts = pp.throttleLatest(1, TimeUnit.SECONDS, sch, true, drops::onNext)
+        .test();
+
+        ts.assertEmpty();
+        drops.assertEmpty();
+
+        pp.onNext(1);
+
+        ts.assertValuesOnly(1);
+        drops.assertEmpty();
+
+        pp.onNext(2);
+
+        ts.assertValuesOnly(1);
+        drops.assertEmpty();
+
+        pp.onNext(3);
+
+        ts.assertValuesOnly(1);
+        drops.assertValuesOnly(2);
+
+        pp.onComplete();
+
+        ts.assertResult(1, 3);
+
+        drops.assertValuesOnly(2);
+    }
+
+    /** Emit 1, 2, 3; 3 should trigger an error to the downstream because 2 is dropped and the callback crashes. */
+    @Test
+    public void onDroppedBasicNoEmitLastFirstDropCrash() throws Throwable {
+        PublishProcessor pp =PublishProcessor.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        Action whenDisposed = mock(Action.class);
+
+        TestSubscriber ts = pp
+        .doOnCancel(whenDisposed)
+        .throttleLatest(1, TimeUnit.SECONDS, sch, false, d -> {
+            if (d == 2) {
+                throw new TestException("forced");
+            }
+        })
+        .test();
+
+        ts.assertEmpty();
+
+        pp.onNext(1);
+
+        ts.assertValuesOnly(1);
+
+        pp.onNext(2);
+
+        ts.assertValuesOnly(1);
+
+        pp.onNext(3);
+
+        ts.assertFailure(TestException.class, 1);
+
+        verify(whenDisposed).run();
+    }
+
+    /**
+     * Emit 1, 2, Error; the error should trigger the drop callback and crash it too,
+     * downstream gets 1, composite(source, drop-crash).
+     */
+    @Test
+    public void onDroppedBasicNoEmitLastOnErrorDropCrash() throws Throwable {
+        PublishProcessor pp =PublishProcessor.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        Action whenDisposed = mock(Action.class);
+
+        TestSubscriberEx ts = pp
+        .doOnCancel(whenDisposed)
+        .throttleLatest(1, TimeUnit.SECONDS, sch, false, d -> { throw new TestException("forced " + d); })
+        .subscribeWith(new TestSubscriberEx<>());
+
+        ts.assertEmpty();
+
+        pp.onNext(1);
+
+        ts.assertValuesOnly(1);
+
+        pp.onNext(2);
+
+        ts.assertValuesOnly(1);
+
+        pp.onError(new TestException("source"));
+
+        ts.assertFailure(CompositeException.class, 1);
+
+        TestHelper.assertCompositeExceptions(ts, TestException.class, "source", TestException.class, "forced 2");
+
+        verify(whenDisposed, never()).run();
+    }
+
+    /**
+     * Emit 1, 2, 3; 3 should trigger a drop-crash for 2, which then would trigger the error path and drop-crash for 3,
+     * the last item not delivered, downstream gets 1, composite(drop-crash 2, drop-crash 3).
+     */
+    @Test
+    public void onDroppedBasicEmitLastOnErrorDropCrash() throws Throwable {
+        PublishProcessor pp =PublishProcessor.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        Action whenDisposed = mock(Action.class);
+
+        TestSubscriberEx ts = pp
+        .doOnCancel(whenDisposed)
+        .throttleLatest(1, TimeUnit.SECONDS, sch, true, d -> { throw new TestException("forced " + d); })
+        .subscribeWith(new TestSubscriberEx<>());
+
+        ts.assertEmpty();
+
+        pp.onNext(1);
+
+        ts.assertValuesOnly(1);
+
+        pp.onNext(2);
+
+        ts.assertValuesOnly(1);
+
+        pp.onNext(3);
+
+        ts.assertFailure(CompositeException.class, 1);
+
+        TestHelper.assertCompositeExceptions(ts, TestException.class, "forced 2", TestException.class, "forced 3");
+
+        verify(whenDisposed).run();
+    }
+
+    /** Emit 1, complete; Downstream gets 1, complete, no drops. */
+    @Test
+    public void onDroppedBasicNoEmitLastNoLastToDrop() {
+        PublishProcessor pp =PublishProcessor.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        TestSubscriber drops = new TestSubscriber<>();
+        drops.onSubscribe(EmptySubscription.INSTANCE);
+
+        TestSubscriber ts = pp.throttleLatest(1, TimeUnit.SECONDS, sch, false, drops::onNext)
+        .test();
+
+        ts.assertEmpty();
+        drops.assertEmpty();
+
+        pp.onNext(1);
+
+        ts.assertValuesOnly(1);
+        drops.assertEmpty();
+
+        pp.onComplete();
+
+        ts.assertResult(1);
+        drops.assertEmpty();
+    }
+
+    /** Emit 1, error; Downstream gets 1, error, no drops. */
+    @Test
+    public void onDroppedErrorNoEmitLastNoLastToDrop() {
+        PublishProcessor pp =PublishProcessor.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        TestSubscriber drops = new TestSubscriber<>();
+        drops.onSubscribe(EmptySubscription.INSTANCE);
+
+        TestSubscriber ts = pp.throttleLatest(1, TimeUnit.SECONDS, sch, false, drops::onNext)
+        .test();
+
+        ts.assertEmpty();
+        drops.assertEmpty();
+
+        pp.onNext(1);
+
+        ts.assertValuesOnly(1);
+        drops.assertEmpty();
+
+        pp.onError(new TestException());
+
+        ts.assertFailure(TestException.class, 1);
+        drops.assertEmpty();
+    }
+
+    /**
+     * Emit 1, 2, complete; complete should crash drop, downstream gets 1, drop-crash 2.
+     */
+    @Test
+    public void onDroppedHasLastNoEmitLastDropCrash() throws Throwable {
+        PublishProcessor pp =PublishProcessor.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        Action whenDisposed = mock(Action.class);
+
+        TestSubscriberEx ts = pp
+        .doOnCancel(whenDisposed)
+        .throttleLatest(1, TimeUnit.SECONDS, sch, false, d -> { throw new TestException("forced " + d); })
+        .subscribeWith(new TestSubscriberEx<>());
+
+        ts.assertEmpty();
+
+        pp.onNext(1);
+
+        ts.assertValuesOnly(1);
+
+        pp.onNext(2);
+
+        ts.assertValuesOnly(1);
+
+        pp.onComplete();
+
+        ts.assertFailureAndMessage(TestException.class, "forced 2", 1);
+
+        verify(whenDisposed, never()).run();
+    }
+
+    /**
+     * Emit 1, 2 then dispose the sequence; downstream gets 1, drop should get for 2.
+     */
+    @Test
+    public void onDroppedDisposeDrops() throws Throwable {
+        PublishProcessor pp =PublishProcessor.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        Action whenDisposed = mock(Action.class);
+
+        TestSubscriber drops = new TestSubscriber<>();
+        drops.onSubscribe(EmptySubscription.INSTANCE);
+
+        TestSubscriberEx ts = pp
+        .doOnCancel(whenDisposed)
+        .throttleLatest(1, TimeUnit.SECONDS, sch, false, drops::onNext)
+        .subscribeWith(new TestSubscriberEx<>());
+
+        ts.assertEmpty();
+
+        pp.onNext(1);
+
+        ts.assertValuesOnly(1);
+
+        pp.onNext(2);
+
+        ts.assertValuesOnly(1);
+
+        ts.cancel();
+
+        ts.assertValuesOnly(1);
+        drops.assertValuesOnly(2);
+
+        verify(whenDisposed).run();
+    }
+
+    /**
+     * Emit 1 then dispose the sequence; downstream gets 1, drop should not get called.
+     */
+    @Test
+    public void onDroppedDisposeNoDrops() throws Throwable {
+        PublishProcessor pp =PublishProcessor.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        Action whenDisposed = mock(Action.class);
+
+        TestSubscriber drops = new TestSubscriber<>();
+        drops.onSubscribe(EmptySubscription.INSTANCE);
+
+        TestSubscriberEx ts = pp
+        .doOnCancel(whenDisposed)
+        .throttleLatest(1, TimeUnit.SECONDS, sch, false, drops::onNext)
+        .subscribeWith(new TestSubscriberEx<>());
+
+        ts.assertEmpty();
+
+        pp.onNext(1);
+
+        ts.assertValuesOnly(1);
+
+        ts.cancel();
+
+        ts.assertValuesOnly(1);
+        drops.assertEmpty();
+
+        verify(whenDisposed).run();
+    }
+
+    /**
+     * Emit 1, 2 then dispose the sequence; downstream gets 1, global error handler should get drop-crash 2.
+     */
+    @Test
+    public void onDroppedDisposeCrashesDrop() throws Throwable {
+        TestHelper.withErrorTracking(errors -> {
+            PublishProcessor pp =PublishProcessor.create();
+
+            TestScheduler sch = new TestScheduler();
+
+            Action whenDisposed = mock(Action.class);
+
+            TestSubscriberEx ts = pp
+            .doOnCancel(whenDisposed)
+            .throttleLatest(1, TimeUnit.SECONDS, sch, false, d -> { throw new TestException("forced " + d); })
+            .subscribeWith(new TestSubscriberEx<>());
+
+            ts.assertEmpty();
+
+            pp.onNext(1);
+
+            ts.assertValuesOnly(1);
+
+            pp.onNext(2);
+
+            ts.assertValuesOnly(1);
+
+            ts.cancel();
+
+            ts.assertValuesOnly(1);
+
+            verify(whenDisposed).run();
+
+            TestHelper.assertUndeliverable(errors, 0, TestException.class, "forced 2");
+        });
+    }
+
+    /** Emit 1 but downstream is backpressured; downstream gets MBE, drops gets 1. */
+    @Test
+    public void onDroppedBackpressured() throws Throwable {
+        PublishProcessor pp =PublishProcessor.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        TestSubscriber drops = new TestSubscriber<>();
+        drops.onSubscribe(EmptySubscription.INSTANCE);
+
+        Action whenDisposed = mock(Action.class);
+
+        TestSubscriber ts = pp
+        .doOnCancel(whenDisposed)
+        .throttleLatest(1, TimeUnit.SECONDS, sch, false, drops::onNext)
+        .test(0L);
+
+        ts.assertEmpty();
+        drops.assertEmpty();
+
+        pp.onNext(1);
+
+        ts.assertFailure(MissingBackpressureException.class);
+
+        drops.assertValuesOnly(1);
+
+        verify(whenDisposed).run();
+    }
+
+    /** Emit 1 but downstream is backpressured; drop crashes, downstream gets composite(MBE, drop-crash 1). */
+    @Test
+    public void onDroppedBackpressuredDropCrash() throws Throwable {
+        PublishProcessor pp =PublishProcessor.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        Action whenDisposed = mock(Action.class);
+
+        TestSubscriberEx ts = pp
+        .doOnCancel(whenDisposed)
+        .throttleLatest(1, TimeUnit.SECONDS, sch, false, d -> { throw new TestException("forced " + d); })
+        .subscribeWith(new TestSubscriberEx<>(0L));
+
+        ts.assertEmpty();
+
+        pp.onNext(1);
+
+        ts.assertFailure(CompositeException.class);
+
+        TestHelper.assertCompositeExceptions(ts,
+                MissingBackpressureException.class, "Could not emit value due to lack of requests",
+                TestException.class, "forced 1");
+
+        verify(whenDisposed).run();
+    }
 }
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableZipTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableZipTest.java
index 47bbd491bd0..8d3e10dbd27 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableZipTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/flowable/FlowableZipTest.java
@@ -1870,7 +1870,7 @@ public Integer apply(Integer a, Integer b) throws Exception {
     public void firstErrorPreventsSecondSubscription() {
         final AtomicInteger counter = new AtomicInteger();
 
-        List> flowableList = new ArrayList<>();
+        List> flowableList = new ArrayList<>();
         flowableList.add(Flowable.create(new FlowableOnSubscribe() {
             @Override
             public void subscribe(FlowableEmitter e)
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/mixed/FlowableConcatMapCompletableTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/mixed/FlowableConcatMapCompletableTest.java
index 048e993b1d3..44acad42b12 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/mixed/FlowableConcatMapCompletableTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/mixed/FlowableConcatMapCompletableTest.java
@@ -285,7 +285,7 @@ protected void subscribeActual(Subscriber s) {
                     Functions.justFunction(Completable.never()), 1
             )
             .test()
-            .assertFailure(MissingBackpressureException.class);
+            .assertFailure(QueueOverflowException.class);
 
             TestHelper.assertUndeliverable(errors, 0, TestException.class);
         } finally {
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/mixed/FlowableConcatMapMaybeTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/mixed/FlowableConcatMapMaybeTest.java
index b2cfdc76d21..12b61a5e8cd 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/mixed/FlowableConcatMapMaybeTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/mixed/FlowableConcatMapMaybeTest.java
@@ -249,7 +249,7 @@ protected void subscribeActual(Subscriber s) {
                     Functions.justFunction(Maybe.never()), 1
             )
             .test()
-            .assertFailure(MissingBackpressureException.class);
+            .assertFailure(QueueOverflowException.class);
 
             TestHelper.assertUndeliverable(errors, 0, TestException.class);
         } finally {
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/mixed/FlowableConcatMapSingleTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/mixed/FlowableConcatMapSingleTest.java
index 6dd081b4ed3..60cb2f5de0b 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/mixed/FlowableConcatMapSingleTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/mixed/FlowableConcatMapSingleTest.java
@@ -167,7 +167,7 @@ protected void subscribeActual(Subscriber s) {
                     Functions.justFunction(Single.never()), 1
             )
             .test()
-            .assertFailure(MissingBackpressureException.class);
+            .assertFailure(QueueOverflowException.class);
 
             TestHelper.assertUndeliverable(errors, 0, TestException.class);
         } finally {
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableAmbTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableAmbTest.java
index 0a349cd4176..5ec9129d9f7 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableAmbTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableAmbTest.java
@@ -235,7 +235,8 @@ public void ambArraySingleElement() {
 
     @Test
     public void manySources() {
-        Observable[] a = new Observable[32];
+        @SuppressWarnings("unchecked")
+        Observable[] a = new Observable[32];
         Arrays.fill(a, Observable.never());
         a[31] = Observable.just(1);
 
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableBufferTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableBufferTest.java
index 8264a66494f..7085720f013 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableBufferTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableBufferTest.java
@@ -1278,9 +1278,9 @@ public Integer apply(Integer integer, Long aLong) {
                             }
                         })
                 .buffer(Observable.interval(0, 200, TimeUnit.MILLISECONDS),
-                        new Function>() {
+                        new Function>() {
                             @Override
-                            public Observable apply(Long a) {
+                            public Observable apply(Long a) {
                                 return Observable.just(a).delay(100, TimeUnit.MILLISECONDS);
                             }
                         })
@@ -1301,9 +1301,9 @@ public Integer apply(Integer integer, Long aLong) {
                             }
                         })
                 .buffer(Observable.interval(0, 100, TimeUnit.MILLISECONDS),
-                        new Function>() {
+                        new Function>() {
                             @Override
-                            public Observable apply(Long a) {
+                            public Observable apply(Long a) {
                                 return Observable.just(a).delay(200, TimeUnit.MILLISECONDS);
                             }
                         })
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableCacheTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableCacheTest.java
index 7f47ec95d8a..74d17c062b2 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableCacheTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableCacheTest.java
@@ -16,10 +16,15 @@
 import static org.junit.Assert.*;
 import static org.mockito.Mockito.*;
 
+import java.lang.management.ManagementFactory;
+import java.lang.management.MemoryMXBean;
+import java.lang.management.MemoryUsage;
 import java.util.*;
 import java.util.concurrent.*;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
 
+import io.reactivex.rxjava3.observables.ConnectableObservable;
 import org.junit.Test;
 
 import io.reactivex.rxjava3.core.*;
@@ -355,4 +360,52 @@ public void addRemoveRace() {
             );
         }
     }
+
+    @Test
+    public void valuesAreReclaimable() throws Exception {
+        ConnectableObservable source =
+                Observable.range(0, 200)
+                        .map($ -> new byte[1024 * 1024])
+                        .publish();
+
+        System.out.println("Bounded Replay Leak check: Wait before GC");
+        Thread.sleep(1000);
+
+        System.out.println("Bounded Replay Leak check: GC");
+        System.gc();
+
+        Thread.sleep(500);
+
+        final MemoryMXBean memoryMXBean = ManagementFactory.getMemoryMXBean();
+        MemoryUsage memHeap = memoryMXBean.getHeapMemoryUsage();
+        long initial = memHeap.getUsed();
+
+        System.out.printf("Bounded Replay Leak check: Starting: %.3f MB%n", initial / 1024.0 / 1024.0);
+
+        final AtomicLong after = new AtomicLong();
+
+        source.cache().lastElement().subscribe(new Consumer() {
+            @Override
+            public void accept(byte[] v) throws Exception {
+                System.out.println("Bounded Replay Leak check: Wait before GC 2");
+                Thread.sleep(1000);
+
+                System.out.println("Bounded Replay Leak check:  GC 2");
+                System.gc();
+
+                Thread.sleep(500);
+
+                after.set(memoryMXBean.getHeapMemoryUsage().getUsed());
+            }
+        });
+
+        source.connect();
+
+        System.out.printf("Bounded Replay Leak check: After: %.3f MB%n", after.get() / 1024.0 / 1024.0);
+
+        if (initial + 100 * 1024 * 1024 < after.get()) {
+            fail("Bounded Replay Leak check: Memory leak detected: " + (initial / 1024.0 / 1024.0)
+                    + " -> " + after.get() / 1024.0 / 1024.0);
+        }
+    }
 }
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableDebounceTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableDebounceTest.java
index b43b1d2d27c..fc4e7d8478d 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableDebounceTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableDebounceTest.java
@@ -21,6 +21,7 @@
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicReference;
 
+import io.reactivex.rxjava3.functions.Action;
 import org.junit.*;
 import org.mockito.InOrder;
 import org.reactivestreams.Publisher;
@@ -50,6 +51,76 @@ public void before() {
         innerScheduler = scheduler.createWorker();
     }
 
+    @Test
+    public void debounceWithOnDroppedCallbackWithEx() throws Throwable {
+        Observable source = Observable.unsafeCreate(new ObservableSource() {
+            @Override
+            public void subscribe(Observer observer) {
+                observer.onSubscribe(Disposable.empty());
+                publishNext(observer, 100, "one");    // Should be skipped since "two" will arrive before the timeout expires.
+                publishNext(observer, 400, "two");    // Should be published since "three" will arrive after the timeout expires.
+                publishNext(observer, 900, "three");   // Should be skipped since onComplete will arrive before the timeout expires.
+                publishNext(observer, 999, "four");   // Should be skipped since onComplete will arrive before the timeout expires.
+                publishCompleted(observer, 1000);     // Should be published as soon as the timeout expires.
+            }
+        });
+
+        Action whenDisposed = mock(Action.class);
+        Observable sampled = source
+                .doOnDispose(whenDisposed)
+                .debounce(400, TimeUnit.MILLISECONDS, scheduler, e -> {
+            if ("three".equals(e)) {
+                throw new TestException("forced");
+            }
+        });
+        sampled.subscribe(observer);
+
+        scheduler.advanceTimeTo(0, TimeUnit.MILLISECONDS);
+        InOrder inOrder = inOrder(observer);
+        // must go to 800 since it must be 400 after when two is sent, which is at 400
+        scheduler.advanceTimeTo(800, TimeUnit.MILLISECONDS);
+        inOrder.verify(observer, times(1)).onNext("two");
+        scheduler.advanceTimeTo(1000, TimeUnit.MILLISECONDS);
+        inOrder.verify(observer, times(1)).onError(any(TestException.class));
+        inOrder.verify(observer, never()).onNext("three");
+        inOrder.verify(observer, never()).onNext("four");
+        inOrder.verify(observer, never()).onComplete();
+        inOrder.verifyNoMoreInteractions();
+        verify(whenDisposed).run();
+    }
+
+    @Test
+    public void debounceWithOnDroppedCallback() {
+        Observable source = Observable.unsafeCreate(new ObservableSource() {
+            @Override
+            public void subscribe(Observer observer) {
+                observer.onSubscribe(Disposable.empty());
+                publishNext(observer, 100, "one");    // Should be skipped since "two" will arrive before the timeout expires.
+                publishNext(observer, 400, "two");    // Should be published since "three" will arrive after the timeout expires.
+                publishNext(observer, 900, "three");   // Should be skipped since onComplete will arrive before the timeout expires.
+                publishNext(observer, 999, "four");   // Should be skipped since onComplete will arrive before the timeout expires.
+                publishCompleted(observer, 1000);     // Should be published as soon as the timeout expires.
+            }
+        });
+
+        Observer drops = TestHelper.mockObserver();
+        InOrder inOrderDrops = inOrder(drops);
+        Observable sampled = source.debounce(400, TimeUnit.MILLISECONDS, scheduler, drops::onNext);
+        sampled.subscribe(observer);
+
+        scheduler.advanceTimeTo(0, TimeUnit.MILLISECONDS);
+        InOrder inOrder = inOrder(observer);
+        // must go to 800 since it must be 400 after when two is sent, which is at 400
+        scheduler.advanceTimeTo(800, TimeUnit.MILLISECONDS);
+        inOrderDrops.verify(drops, times(1)).onNext("one");
+        inOrder.verify(observer, times(1)).onNext("two");
+        scheduler.advanceTimeTo(1000, TimeUnit.MILLISECONDS);
+        inOrderDrops.verify(drops, times(1)).onNext("three");
+        inOrder.verify(observer, times(1)).onComplete();
+        inOrder.verifyNoMoreInteractions();
+        inOrderDrops.verifyNoMoreInteractions();
+    }
+
     @Test
     public void debounceWithCompleted() {
         Observable source = Observable.unsafeCreate(new ObservableSource() {
@@ -489,7 +560,7 @@ protected void subscribeActual(
     public void timedLateEmit() {
         TestObserver to = new TestObserver<>();
         DebounceTimedObserver sub = new DebounceTimedObserver<>(
-                to, 1, TimeUnit.SECONDS, new TestScheduler().createWorker());
+                to, 1, TimeUnit.SECONDS, new TestScheduler().createWorker(), null);
 
         sub.onSubscribe(Disposable.empty());
 
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableDelayTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableDelayTest.java
index ea8d51d9962..778d2d4e64d 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableDelayTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableDelayTest.java
@@ -20,6 +20,7 @@
 import java.util.*;
 import java.util.concurrent.*;
 import java.util.concurrent.atomic.AtomicReference;
+import java.util.concurrent.locks.LockSupport;
 
 import org.junit.*;
 import org.mockito.InOrder;
@@ -29,6 +30,7 @@
 import io.reactivex.rxjava3.core.Observer;
 import io.reactivex.rxjava3.exceptions.TestException;
 import io.reactivex.rxjava3.functions.*;
+import io.reactivex.rxjava3.internal.disposables.SequentialDisposable;
 import io.reactivex.rxjava3.internal.functions.Functions;
 import io.reactivex.rxjava3.observers.*;
 import io.reactivex.rxjava3.schedulers.*;
@@ -978,4 +980,37 @@ public Observable apply(Integer t) throws Exception {
         .to(TestHelper.testConsumer())
         .assertFailureAndMessage(NullPointerException.class, "The itemDelay returned a null ObservableSource");
     }
-}
+
+    @Test
+    public void cancelShouldPreventRandomSubsequentEmissions() {
+        for (int attempt = 1; attempt < 100; attempt ++) {
+
+            SequentialDisposable disposable = new SequentialDisposable();
+            ConcurrentLinkedQueue sink = new ConcurrentLinkedQueue<>();
+
+            disposable.replace(
+                Observable.range(1, 10)
+                .delay(1, TimeUnit.MICROSECONDS, Schedulers.computation(), true)
+                .doOnNext(v -> {
+                    if (v == 1) {
+                        Schedulers.computation().scheduleDirect(disposable::dispose);
+                    }
+                    sink.offer(v);
+                })
+            .subscribe());
+
+            LockSupport.parkNanos(TimeUnit.MILLISECONDS.toNanos(1));
+
+            Integer last = null;
+
+            while (!sink.isEmpty()) {
+                Integer current = sink.poll();
+
+                if (last != null && last + 1 != current) {
+                    fail("Emission hole: " + last + " -> " + current);
+                }
+
+                last = current;
+            }
+        }
+    }}
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableSwitchTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableSwitchTest.java
index ffa4049a448..72e6c93bb85 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableSwitchTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableSwitchTest.java
@@ -1438,4 +1438,19 @@ Observable createObservable(AtomicInteger inner) {
             inner.incrementAndGet();
         });
     }
+
+    @Test
+    public void innerOnSubscribeOuterCancelRace() {
+        TestObserver to = new TestObserver();
+
+        Observable.just(1)
+        .hide()
+        .switchMap(v -> Observable.just(1)
+                .doOnSubscribe(d -> to.dispose())
+                .scan(1, (a, b) -> a)
+        )
+        .subscribe(to);
+
+        to.assertEmpty();
+    }
 }
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableThrottleFirstTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableThrottleFirstTest.java
index 64c0a8dae0a..fe296d572bc 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableThrottleFirstTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableThrottleFirstTest.java
@@ -18,6 +18,7 @@
 
 import java.util.concurrent.TimeUnit;
 
+import io.reactivex.rxjava3.functions.Action;
 import org.junit.*;
 import org.mockito.InOrder;
 
@@ -41,6 +42,76 @@ public void before() {
         observer = TestHelper.mockObserver();
     }
 
+    @Test
+    public void throttlingWithDropCallbackCrashes() throws Throwable {
+        Observable source = Observable.unsafeCreate(new ObservableSource() {
+            @Override
+            public void subscribe(Observer innerObserver) {
+                innerObserver.onSubscribe(Disposable.empty());
+                publishNext(innerObserver, 100, "one");    // publish as it's first
+                publishNext(innerObserver, 300, "two");    // skip as it's last within the first 400
+                publishNext(innerObserver, 900, "three");   // publish
+                publishNext(innerObserver, 905, "four");   // skip
+                publishCompleted(innerObserver, 1000);     // Should be published as soon as the timeout expires.
+            }
+        });
+
+        Action whenDisposed = mock(Action.class);
+        Observable sampled = source
+                .doOnDispose(whenDisposed)
+                .throttleFirst(400, TimeUnit.MILLISECONDS, scheduler, e -> {
+                    if ("two".equals(e)) {
+                        throw new TestException("forced");
+                    }
+                });
+        sampled.subscribe(observer);
+
+        InOrder inOrder = inOrder(observer);
+
+        scheduler.advanceTimeTo(1000, TimeUnit.MILLISECONDS);
+        inOrder.verify(observer, times(1)).onNext("one");
+        inOrder.verify(observer, times(1)).onError(any(TestException.class));
+        inOrder.verify(observer, times(0)).onNext("two");
+        inOrder.verify(observer, times(0)).onNext("three");
+        inOrder.verify(observer, times(0)).onNext("four");
+        inOrder.verify(observer, times(0)).onComplete();
+        inOrder.verifyNoMoreInteractions();
+        verify(whenDisposed).run();
+    }
+
+    @Test
+    public void throttlingWithDropCallback() {
+        Observable source = Observable.unsafeCreate(new ObservableSource() {
+            @Override
+            public void subscribe(Observer innerObserver) {
+                innerObserver.onSubscribe(Disposable.empty());
+                publishNext(innerObserver, 100, "one");    // publish as it's first
+                publishNext(innerObserver, 300, "two");    // skip as it's last within the first 400
+                publishNext(innerObserver, 900, "three");   // publish
+                publishNext(innerObserver, 905, "four");   // skip
+                publishCompleted(innerObserver, 1000);     // Should be published as soon as the timeout expires.
+            }
+        });
+
+        Observer dropCallbackObserver = TestHelper.mockObserver();
+        Observable sampled = source.throttleFirst(400, TimeUnit.MILLISECONDS, scheduler, dropCallbackObserver::onNext);
+        sampled.subscribe(observer);
+
+        InOrder inOrder = inOrder(observer);
+        InOrder dropCallbackOrder = inOrder(dropCallbackObserver);
+
+        scheduler.advanceTimeTo(1000, TimeUnit.MILLISECONDS);
+        inOrder.verify(observer, times(1)).onNext("one");
+        inOrder.verify(observer, times(0)).onNext("two");
+        dropCallbackOrder.verify(dropCallbackObserver, times(1)).onNext("two");
+        inOrder.verify(observer, times(1)).onNext("three");
+        inOrder.verify(observer, times(0)).onNext("four");
+        dropCallbackOrder.verify(dropCallbackObserver, times(1)).onNext("four");
+        inOrder.verify(observer, times(1)).onComplete();
+        inOrder.verifyNoMoreInteractions();
+        dropCallbackOrder.verifyNoMoreInteractions();
+    }
+
     @Test
     public void throttlingWithCompleted() {
         Observable source = Observable.unsafeCreate(new ObservableSource() {
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableThrottleLatestTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableThrottleLatestTest.java
index c36d04babe5..e1c15f3b1a1 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableThrottleLatestTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableThrottleLatestTest.java
@@ -20,12 +20,13 @@
 import org.junit.Test;
 
 import io.reactivex.rxjava3.core.*;
-import io.reactivex.rxjava3.exceptions.TestException;
+import io.reactivex.rxjava3.disposables.Disposable;
+import io.reactivex.rxjava3.exceptions.*;
 import io.reactivex.rxjava3.functions.*;
 import io.reactivex.rxjava3.observers.TestObserver;
 import io.reactivex.rxjava3.schedulers.TestScheduler;
 import io.reactivex.rxjava3.subjects.PublishSubject;
-import io.reactivex.rxjava3.testsupport.TestHelper;
+import io.reactivex.rxjava3.testsupport.*;
 
 public class ObservableThrottleLatestTest extends RxJavaTest {
 
@@ -221,4 +222,424 @@ public void onNext(Integer t) {
 
         to.assertResult(1, 2);
     }
+
+    /** Emit 1, 2, 3, then advance time by a second; 1 and 3 should end up in downstream, 2 should be dropped. */
+    @Test
+    public void onDroppedBasicNoEmitLast() {
+        PublishSubject ps = PublishSubject.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        TestObserver drops = new TestObserver<>();
+        drops.onSubscribe(Disposable.empty());
+
+        TestObserver to = ps.throttleLatest(1, TimeUnit.SECONDS, sch, false, drops::onNext)
+        .test();
+
+        to.assertEmpty();
+        drops.assertEmpty();
+
+        ps.onNext(1);
+
+        to.assertValuesOnly(1);
+        drops.assertEmpty();
+
+        ps.onNext(2);
+
+        to.assertValuesOnly(1);
+        drops.assertEmpty();
+
+        ps.onNext(3);
+
+        to.assertValuesOnly(1);
+        drops.assertValuesOnly(2);
+
+        sch.advanceTimeBy(1, TimeUnit.SECONDS);
+
+        to.assertValuesOnly(1, 3);
+        drops.assertValuesOnly(2);
+
+        ps.onComplete();
+
+        to.assertResult(1, 3);
+
+        drops.assertValuesOnly(2);
+    }
+
+    /** Emit 1, 2, 3; 1 should end up in downstream, 2, 3 should be dropped. */
+    @Test
+    public void onDroppedBasicNoEmitLastDropLast() {
+        PublishSubject ps = PublishSubject.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        TestObserver drops = new TestObserver<>();
+        drops.onSubscribe(Disposable.empty());
+
+        TestObserver to = ps.throttleLatest(1, TimeUnit.SECONDS, sch, false, drops::onNext)
+        .test();
+
+        to.assertEmpty();
+        drops.assertEmpty();
+
+        ps.onNext(1);
+
+        to.assertValuesOnly(1);
+        drops.assertEmpty();
+
+        ps.onNext(2);
+
+        to.assertValuesOnly(1);
+        drops.assertEmpty();
+
+        ps.onNext(3);
+
+        to.assertValuesOnly(1);
+        drops.assertValuesOnly(2);
+
+        ps.onComplete();
+
+        to.assertResult(1);
+
+        drops.assertValuesOnly(2, 3);
+    }
+
+    /** Emit 1, 2, 3; 1 and 3 should end up in downstream, 2 should be dropped. */
+    @Test
+    public void onDroppedBasicEmitLast() {
+        PublishSubject ps = PublishSubject.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        TestObserver drops = new TestObserver<>();
+        drops.onSubscribe(Disposable.empty());
+
+        TestObserver to = ps.throttleLatest(1, TimeUnit.SECONDS, sch, true, drops::onNext)
+        .test();
+
+        to.assertEmpty();
+        drops.assertEmpty();
+
+        ps.onNext(1);
+
+        to.assertValuesOnly(1);
+        drops.assertEmpty();
+
+        ps.onNext(2);
+
+        to.assertValuesOnly(1);
+        drops.assertEmpty();
+
+        ps.onNext(3);
+
+        to.assertValuesOnly(1);
+        drops.assertValuesOnly(2);
+
+        ps.onComplete();
+
+        to.assertResult(1, 3);
+
+        drops.assertValuesOnly(2);
+    }
+
+    /** Emit 1, 2, 3; 3 should trigger an error to the downstream because 2 is dropped and the callback crashes. */
+    @Test
+    public void onDroppedBasicNoEmitLastFirstDropCrash() throws Throwable {
+        PublishSubject ps = PublishSubject.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        Action whenDisposed = mock(Action.class);
+
+        TestObserver to = ps
+        .doOnDispose(whenDisposed)
+        .throttleLatest(1, TimeUnit.SECONDS, sch, false, d -> {
+            if (d == 2) {
+                throw new TestException("forced");
+            }
+        })
+        .test();
+
+        to.assertEmpty();
+
+        ps.onNext(1);
+
+        to.assertValuesOnly(1);
+
+        ps.onNext(2);
+
+        to.assertValuesOnly(1);
+
+        ps.onNext(3);
+
+        to.assertFailure(TestException.class, 1);
+
+        verify(whenDisposed).run();
+    }
+
+    /**
+     * Emit 1, 2, Error; the error should trigger the drop callback and crash it too,
+     * downstream gets 1, composite(source, drop-crash).
+     */
+    @Test
+    public void onDroppedBasicNoEmitLastOnErrorDropCrash() throws Throwable {
+        PublishSubject ps = PublishSubject.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        Action whenDisposed = mock(Action.class);
+
+        TestObserverEx to = ps
+        .doOnDispose(whenDisposed)
+        .throttleLatest(1, TimeUnit.SECONDS, sch, false, d -> { throw new TestException("forced " + d); })
+        .subscribeWith(new TestObserverEx<>());
+
+        to.assertEmpty();
+
+        ps.onNext(1);
+
+        to.assertValuesOnly(1);
+
+        ps.onNext(2);
+
+        to.assertValuesOnly(1);
+
+        ps.onError(new TestException("source"));
+
+        to.assertFailure(CompositeException.class, 1);
+
+        TestHelper.assertCompositeExceptions(to, TestException.class, "source", TestException.class, "forced 2");
+
+        verify(whenDisposed, never()).run();
+    }
+
+    /**
+     * Emit 1, 2, 3; 3 should trigger a drop-crash for 2, which then would trigger the error path and drop-crash for 3,
+     * the last item not delivered, downstream gets 1, composite(drop-crash 2, drop-crash 3).
+     */
+    @Test
+    public void onDroppedBasicEmitLastOnErrorDropCrash() throws Throwable {
+        PublishSubject ps = PublishSubject.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        Action whenDisposed = mock(Action.class);
+
+        TestObserverEx to = ps
+        .doOnDispose(whenDisposed)
+        .throttleLatest(1, TimeUnit.SECONDS, sch, true, d -> { throw new TestException("forced " + d); })
+        .subscribeWith(new TestObserverEx<>());
+
+        to.assertEmpty();
+
+        ps.onNext(1);
+
+        to.assertValuesOnly(1);
+
+        ps.onNext(2);
+
+        to.assertValuesOnly(1);
+
+        ps.onNext(3);
+
+        to.assertFailure(CompositeException.class, 1);
+
+        TestHelper.assertCompositeExceptions(to, TestException.class, "forced 2", TestException.class, "forced 3");
+
+        verify(whenDisposed).run();
+    }
+
+    /** Emit 1, complete; Downstream gets 1, complete, no drops. */
+    @Test
+    public void onDroppedBasicNoEmitLastNoLastToDrop() {
+        PublishSubject ps = PublishSubject.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        TestObserver drops = new TestObserver<>();
+        drops.onSubscribe(Disposable.empty());
+
+        TestObserver to = ps.throttleLatest(1, TimeUnit.SECONDS, sch, false, drops::onNext)
+        .test();
+
+        to.assertEmpty();
+        drops.assertEmpty();
+
+        ps.onNext(1);
+
+        to.assertValuesOnly(1);
+        drops.assertEmpty();
+
+        ps.onComplete();
+
+        to.assertResult(1);
+        drops.assertEmpty();
+    }
+
+    /** Emit 1, error; Downstream gets 1, error, no drops. */
+    @Test
+    public void onDroppedErrorNoEmitLastNoLastToDrop() {
+        PublishSubject ps = PublishSubject.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        TestObserver drops = new TestObserver<>();
+        drops.onSubscribe(Disposable.empty());
+
+        TestObserver to = ps.throttleLatest(1, TimeUnit.SECONDS, sch, false, drops::onNext)
+        .test();
+
+        to.assertEmpty();
+        drops.assertEmpty();
+
+        ps.onNext(1);
+
+        to.assertValuesOnly(1);
+        drops.assertEmpty();
+
+        ps.onError(new TestException());
+
+        to.assertFailure(TestException.class, 1);
+        drops.assertEmpty();
+    }
+
+    /**
+     * Emit 1, 2, complete; complete should crash drop, downstream gets 1, drop-crash 2.
+     */
+    @Test
+    public void onDroppedHasLastNoEmitLastDropCrash() throws Throwable {
+        PublishSubject ps = PublishSubject.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        Action whenDisposed = mock(Action.class);
+
+        TestObserverEx to = ps
+        .doOnDispose(whenDisposed)
+        .throttleLatest(1, TimeUnit.SECONDS, sch, false, d -> { throw new TestException("forced " + d); })
+        .subscribeWith(new TestObserverEx<>());
+
+        to.assertEmpty();
+
+        ps.onNext(1);
+
+        to.assertValuesOnly(1);
+
+        ps.onNext(2);
+
+        to.assertValuesOnly(1);
+
+        ps.onComplete();
+
+        to.assertFailureAndMessage(TestException.class, "forced 2", 1);
+
+        verify(whenDisposed, never()).run();
+    }
+
+    /**
+     * Emit 1, 2 then dispose the sequence; downstream gets 1, drop should get for 2.
+     */
+    @Test
+    public void onDroppedDisposeDrops() throws Throwable {
+        PublishSubject ps = PublishSubject.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        Action whenDisposed = mock(Action.class);
+
+        TestObserver drops = new TestObserver<>();
+        drops.onSubscribe(Disposable.empty());
+
+        TestObserverEx to = ps
+        .doOnDispose(whenDisposed)
+        .throttleLatest(1, TimeUnit.SECONDS, sch, false, drops::onNext)
+        .subscribeWith(new TestObserverEx<>());
+
+        to.assertEmpty();
+
+        ps.onNext(1);
+
+        to.assertValuesOnly(1);
+
+        ps.onNext(2);
+
+        to.assertValuesOnly(1);
+
+        to.dispose();
+
+        to.assertValuesOnly(1);
+        drops.assertValuesOnly(2);
+
+        verify(whenDisposed).run();
+    }
+
+    /**
+     * Emit 1 then dispose the sequence; downstream gets 1, drop should not get called.
+     */
+    @Test
+    public void onDroppedDisposeNoDrops() throws Throwable {
+        PublishSubject ps = PublishSubject.create();
+
+        TestScheduler sch = new TestScheduler();
+
+        Action whenDisposed = mock(Action.class);
+
+        TestObserver drops = new TestObserver<>();
+        drops.onSubscribe(Disposable.empty());
+
+        TestObserverEx to = ps
+        .doOnDispose(whenDisposed)
+        .throttleLatest(1, TimeUnit.SECONDS, sch, false, drops::onNext)
+        .subscribeWith(new TestObserverEx<>());
+
+        to.assertEmpty();
+
+        ps.onNext(1);
+
+        to.assertValuesOnly(1);
+
+        to.dispose();
+
+        to.assertValuesOnly(1);
+        drops.assertEmpty();
+
+        verify(whenDisposed).run();
+    }
+
+    /**
+     * Emit 1, 2 then dispose the sequence; downstream gets 1, global error handler should get drop-crash 2.
+     */
+    @Test
+    public void onDroppedDisposeCrashesDrop() throws Throwable {
+        TestHelper.withErrorTracking(errors -> {
+            PublishSubject ps = PublishSubject.create();
+
+            TestScheduler sch = new TestScheduler();
+
+            Action whenDisposed = mock(Action.class);
+
+            TestObserverEx to = ps
+            .doOnDispose(whenDisposed)
+            .throttleLatest(1, TimeUnit.SECONDS, sch, false, d -> { throw new TestException("forced " + d); })
+            .subscribeWith(new TestObserverEx<>());
+
+            to.assertEmpty();
+
+            ps.onNext(1);
+
+            to.assertValuesOnly(1);
+
+            ps.onNext(2);
+
+            to.assertValuesOnly(1);
+
+            to.dispose();
+
+            to.assertValuesOnly(1);
+
+            verify(whenDisposed).run();
+
+            TestHelper.assertUndeliverable(errors, 0, TestException.class, "forced 2");
+        });
+    }
 }
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableZipTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableZipTest.java
index ae7de66d6f9..faebee3fa55 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableZipTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/observable/ObservableZipTest.java
@@ -1403,7 +1403,7 @@ public Integer apply(Integer t1, Integer t2) throws Exception {
     public void firstErrorPreventsSecondSubscription() {
         final AtomicInteger counter = new AtomicInteger();
 
-        List> observableList = new ArrayList<>();
+        List> observableList = new ArrayList<>();
         observableList.add(Observable.create(new ObservableOnSubscribe() {
             @Override
             public void subscribe(ObservableEmitter e)
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/single/SingleAmbTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/single/SingleAmbTest.java
index 083ee462388..8086aa7c1ca 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/single/SingleAmbTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/single/SingleAmbTest.java
@@ -249,7 +249,8 @@ public void run() {
 
     @Test
     public void manySources() {
-        Single[] sources = new Single[32];
+        @SuppressWarnings("unchecked")
+        Single[] sources = new Single[32];
         Arrays.fill(sources, Single.never());
         sources[31] = Single.just(31);
 
diff --git a/src/test/java/io/reactivex/rxjava3/internal/operators/single/SingleTimeoutTest.java b/src/test/java/io/reactivex/rxjava3/internal/operators/single/SingleTimeoutTest.java
index dcc526c4f63..e54fc112077 100644
--- a/src/test/java/io/reactivex/rxjava3/internal/operators/single/SingleTimeoutTest.java
+++ b/src/test/java/io/reactivex/rxjava3/internal/operators/single/SingleTimeoutTest.java
@@ -28,7 +28,7 @@
 import io.reactivex.rxjava3.functions.Action;
 import io.reactivex.rxjava3.observers.TestObserver;
 import io.reactivex.rxjava3.plugins.RxJavaPlugins;
-import io.reactivex.rxjava3.schedulers.TestScheduler;
+import io.reactivex.rxjava3.schedulers.*;
 import io.reactivex.rxjava3.subjects.*;
 import io.reactivex.rxjava3.testsupport.TestHelper;
 
@@ -255,4 +255,24 @@ protected void subscribeActual(@NonNull SingleObserver
 
         assertTrue(d.isDisposed());
     }
+
+    @Test
+    public void timeoutWithZero() throws InterruptedException {
+        int n = 10_000;
+        Scheduler sch = Schedulers.single();
+        for (int i = 0; i < n; i++) {
+            final int y = i;
+            final CountDownLatch latch = new CountDownLatch(1);
+            Disposable d = Single.never()
+                    .timeout(0, TimeUnit.NANOSECONDS, sch)
+                    .subscribe(v -> {}, e -> {
+                        //System.out.println("timeout " + y);
+                        latch.countDown();
+                    });
+            if (!latch.await(2, TimeUnit.SECONDS)) {
+                System.out.println(d + " " + sch);
+                throw new IllegalStateException("Timeout did not work at y = " + y);
+            }
+        }
+    }
 }
diff --git a/src/test/java/io/reactivex/rxjava3/observable/ObservableThrottleLastTests.java b/src/test/java/io/reactivex/rxjava3/observable/ObservableThrottleLastTests.java
index 735bc4a3122..d8107cc4344 100644
--- a/src/test/java/io/reactivex/rxjava3/observable/ObservableThrottleLastTests.java
+++ b/src/test/java/io/reactivex/rxjava3/observable/ObservableThrottleLastTests.java
@@ -13,10 +13,10 @@
 
 package io.reactivex.rxjava3.observable;
 
-import static org.mockito.Mockito.inOrder;
-
 import java.util.concurrent.TimeUnit;
 
+import io.reactivex.rxjava3.exceptions.TestException;
+import io.reactivex.rxjava3.functions.Action;
 import org.junit.Test;
 import org.mockito.InOrder;
 
@@ -25,8 +25,78 @@
 import io.reactivex.rxjava3.subjects.PublishSubject;
 import io.reactivex.rxjava3.testsupport.TestHelper;
 
+import static org.mockito.Mockito.*;
+
 public class ObservableThrottleLastTests extends RxJavaTest {
 
+    @Test
+    public void throttleLastWithDropCallbackException() throws Throwable {
+        Observer observer = TestHelper.mockObserver();
+
+        Action whenDisposed = mock(Action.class);
+
+        TestScheduler s = new TestScheduler();
+        PublishSubject o = PublishSubject.create();
+        o.doOnDispose(whenDisposed)
+                .throttleLast(500, TimeUnit.MILLISECONDS, s, e -> {
+                    if (e == 1) {
+                        throw new TestException("Forced");
+                    }
+                })
+                .subscribe(observer);
+
+        // send events with simulated time increments
+        s.advanceTimeTo(0, TimeUnit.MILLISECONDS);
+        o.onNext(1); // skip
+        o.onNext(2); // try to deliver
+        s.advanceTimeTo(501, TimeUnit.MILLISECONDS);
+
+        InOrder inOrder = inOrder(observer);
+        inOrder.verify(observer).onError(any(TestException.class));
+        inOrder.verifyNoMoreInteractions();
+        verify(whenDisposed).run();
+    }
+
+    @Test
+    public void throttleLastWithDropCallback() {
+        Observer observer = TestHelper.mockObserver();
+
+        Observer dropCallbackObserver = TestHelper.mockObserver();
+
+        TestScheduler s = new TestScheduler();
+        PublishSubject o = PublishSubject.create();
+        o.throttleLast(500, TimeUnit.MILLISECONDS, s, dropCallbackObserver::onNext).subscribe(observer);
+
+        // send events with simulated time increments
+        s.advanceTimeTo(0, TimeUnit.MILLISECONDS);
+        o.onNext(1); // skip
+        o.onNext(2); // deliver
+        s.advanceTimeTo(501, TimeUnit.MILLISECONDS);
+        o.onNext(3); // skip
+        s.advanceTimeTo(600, TimeUnit.MILLISECONDS);
+        o.onNext(4); // skip
+        s.advanceTimeTo(700, TimeUnit.MILLISECONDS);
+        o.onNext(5); // skip
+        o.onNext(6); // deliver
+        s.advanceTimeTo(1001, TimeUnit.MILLISECONDS);
+        o.onNext(7); // deliver
+        s.advanceTimeTo(1501, TimeUnit.MILLISECONDS);
+        o.onComplete();
+
+        InOrder inOrder = inOrder(observer);
+        InOrder dropCallbackOrder = inOrder(dropCallbackObserver);
+        dropCallbackOrder.verify(dropCallbackObserver).onNext(1);
+        inOrder.verify(observer).onNext(2);
+        dropCallbackOrder.verify(dropCallbackObserver).onNext(3);
+        dropCallbackOrder.verify(dropCallbackObserver).onNext(4);
+        dropCallbackOrder.verify(dropCallbackObserver).onNext(5);
+        inOrder.verify(observer).onNext(6);
+        inOrder.verify(observer).onNext(7);
+        inOrder.verify(observer).onComplete();
+        inOrder.verifyNoMoreInteractions();
+        dropCallbackOrder.verifyNoMoreInteractions();
+    }
+
     @Test
     public void throttle() {
         Observer observer = TestHelper.mockObserver();
diff --git a/src/test/java/io/reactivex/rxjava3/parallel/ParallelFromPublisherTest.java b/src/test/java/io/reactivex/rxjava3/parallel/ParallelFromPublisherTest.java
index c0aafdd6a62..7d4e684bb68 100644
--- a/src/test/java/io/reactivex/rxjava3/parallel/ParallelFromPublisherTest.java
+++ b/src/test/java/io/reactivex/rxjava3/parallel/ParallelFromPublisherTest.java
@@ -50,7 +50,7 @@ protected void subscribeActual(Subscriber s) {
         .parallel(1, 1)
         .sequential(1)
         .test(0)
-        .assertFailure(MissingBackpressureException.class);
+        .assertFailure(QueueOverflowException.class);
     }
 
     @Test
diff --git a/src/test/java/io/reactivex/rxjava3/parallel/ParallelJoinTest.java b/src/test/java/io/reactivex/rxjava3/parallel/ParallelJoinTest.java
index f51b3519e79..8ee41cb9739 100644
--- a/src/test/java/io/reactivex/rxjava3/parallel/ParallelJoinTest.java
+++ b/src/test/java/io/reactivex/rxjava3/parallel/ParallelJoinTest.java
@@ -48,7 +48,7 @@ public int parallelism() {
         }
         .sequential(1)
         .test(0)
-        .assertFailure(MissingBackpressureException.class);
+        .assertFailure(QueueOverflowException.class);
     }
 
     @Test
@@ -81,7 +81,7 @@ public int parallelism() {
         .sequential(1)
         .subscribe(ts);
 
-        ts.assertFailure(MissingBackpressureException.class, 1);
+        ts.assertFailure(QueueOverflowException.class, 1);
     }
 
     @Test
@@ -111,7 +111,7 @@ public int parallelism() {
         .sequentialDelayError(1)
         .test(0)
         .requestMore(1)
-        .assertFailure(MissingBackpressureException.class, 1);
+        .assertFailure(QueueOverflowException.class, 1);
     }
 
     @Test
@@ -148,7 +148,7 @@ public int parallelism() {
 
         ts.request(1);
 
-        ts.assertFailure(MissingBackpressureException.class, 1, 2);
+        ts.assertFailure(QueueOverflowException.class, 1, 2);
     }
 
     @Test
diff --git a/src/test/java/io/reactivex/rxjava3/parallel/ParallelRunOnTest.java b/src/test/java/io/reactivex/rxjava3/parallel/ParallelRunOnTest.java
index 6868e03875b..44a860263a7 100644
--- a/src/test/java/io/reactivex/rxjava3/parallel/ParallelRunOnTest.java
+++ b/src/test/java/io/reactivex/rxjava3/parallel/ParallelRunOnTest.java
@@ -98,7 +98,7 @@ public void subscribe(Subscriber[] subscribers) {
         .runOn(ImmediateThinScheduler.INSTANCE, 1)
         .sequential(1)
         .test(0)
-        .assertFailure(MissingBackpressureException.class);
+        .assertFailure(QueueOverflowException.class);
     }
 
     @Test
diff --git a/src/test/java/io/reactivex/rxjava3/processors/ReplayProcessorTest.java b/src/test/java/io/reactivex/rxjava3/processors/ReplayProcessorTest.java
index aa7026a9ff0..35a877911bb 100644
--- a/src/test/java/io/reactivex/rxjava3/processors/ReplayProcessorTest.java
+++ b/src/test/java/io/reactivex/rxjava3/processors/ReplayProcessorTest.java
@@ -1832,4 +1832,69 @@ public void timeAndSizeRemoveCorrectNumberOfOld() {
 
         rp.test().assertValuesOnly(4, 5);
     }
-}
+
+    @Test
+    public void terminationSubscriptionRaceUnbounded() throws Throwable {
+        for (int i = 1; i <= 10000; i++) {
+            ReplayProcessor source = ReplayProcessor.create();
+            PublishProcessor sink = PublishProcessor.create();
+            TestSubscriber subscriber = sink.test();
+            Schedulers.computation().scheduleDirect(() -> {
+                // issue signals to the source in adherence to the reactive streams specification
+                source.onSubscribe(new BooleanSubscription());
+                source.onNext("hello");
+                source.onNext("world");
+                source.onComplete();
+            });
+            Schedulers.computation().scheduleDirect(() -> {
+                // connect the source to the sink in parallel with the signals issued to the source
+                // note the cast() operator, which is here to detect non-String escapees
+                source.cast(String.class).subscribe(sink);
+            });
+            subscriber.await().assertValues("hello", "world").assertComplete();
+        }
+    }
+
+    @Test
+    public void terminationSubscriptionRaceSizeBound() throws Throwable {
+        for (int i = 1; i <= 10000; i++) {
+            ReplayProcessor source = ReplayProcessor.createWithSize(20);
+            PublishProcessor sink = PublishProcessor.create();
+            TestSubscriber subscriber = sink.test();
+            Schedulers.computation().scheduleDirect(() -> {
+                // issue signals to the source in adherence to the reactive streams specification
+                source.onSubscribe(new BooleanSubscription());
+                source.onNext("hello");
+                source.onNext("world");
+                source.onComplete();
+            });
+            Schedulers.computation().scheduleDirect(() -> {
+                // connect the source to the sink in parallel with the signals issued to the source
+                // note the cast() operator, which is here to detect non-String escapees
+                source.cast(String.class).subscribe(sink);
+            });
+            subscriber.await().assertValues("hello", "world").assertComplete();
+        }
+    }
+
+    @Test
+    public void terminationSubscriptionRaceTimeBound() throws Throwable {
+        for (int i = 1; i <= 10000; i++) {
+            ReplayProcessor source = ReplayProcessor.createWithTime(20, TimeUnit.MINUTES, Schedulers.computation());
+            PublishProcessor sink = PublishProcessor.create();
+            TestSubscriber subscriber = sink.test();
+            Schedulers.computation().scheduleDirect(() -> {
+                // issue signals to the source in adherence to the reactive streams specification
+                source.onSubscribe(new BooleanSubscription());
+                source.onNext("hello");
+                source.onNext("world");
+                source.onComplete();
+            });
+            Schedulers.computation().scheduleDirect(() -> {
+                // connect the source to the sink in parallel with the signals issued to the source
+                // note the cast() operator, which is here to detect non-String escapees
+                source.cast(String.class).subscribe(sink);
+            });
+            subscriber.await().assertValues("hello", "world").assertComplete();
+        }
+    }}
diff --git a/src/test/java/io/reactivex/rxjava3/schedulers/ExecutorSchedulerInterruptibleTest.java b/src/test/java/io/reactivex/rxjava3/schedulers/ExecutorSchedulerInterruptibleTest.java
index f4b5f82ec48..074ac8039a7 100644
--- a/src/test/java/io/reactivex/rxjava3/schedulers/ExecutorSchedulerInterruptibleTest.java
+++ b/src/test/java/io/reactivex/rxjava3/schedulers/ExecutorSchedulerInterruptibleTest.java
@@ -965,4 +965,149 @@ public void run() {
             exec.shutdown();
         }
     }
+
+    public static class TrackInterruptScheduledExecutor extends ScheduledThreadPoolExecutor {
+
+        public final AtomicBoolean interruptReceived = new AtomicBoolean();
+
+        public TrackInterruptScheduledExecutor() {
+            super(10);
+        }
+
+        @Override
+        public  ScheduledFuture schedule(Callable callable, long delay, TimeUnit unit) {
+            return new TrackingScheduledFuture(super.schedule(callable, delay, unit));
+        }
+
+        class TrackingScheduledFuture implements ScheduledFuture {
+
+            ScheduledFuture original;
+
+            TrackingScheduledFuture(ScheduledFuture original) {
+                this.original = original;
+            }
+
+            @Override
+            public long getDelay(TimeUnit unit) {
+                return original.getDelay(unit);
+            }
+
+            @Override
+            public int compareTo(Delayed o) {
+                return original.compareTo(o);
+            }
+
+            @Override
+            public boolean cancel(boolean mayInterruptIfRunning) {
+                if (mayInterruptIfRunning) {
+                    interruptReceived.set(true);
+                }
+                return original.cancel(mayInterruptIfRunning);
+            }
+
+            @Override
+            public boolean isCancelled() {
+                return original.isCancelled();
+            }
+
+            @Override
+            public boolean isDone() {
+                return original.isDone();
+            }
+
+            @Override
+            public V get() throws InterruptedException, ExecutionException {
+                return original.get();
+            }
+
+            @Override
+            public V get(long timeout, TimeUnit unit)
+                    throws InterruptedException, ExecutionException, TimeoutException {
+                return get(timeout, unit);
+            }
+        }
+    }
+
+    @Test
+    public void noInterruptBeforeRunningDelayedWorker() throws Throwable {
+        TrackInterruptScheduledExecutor exec = new TrackInterruptScheduledExecutor();
+
+        try {
+            Scheduler sch = Schedulers.from(exec, false);
+
+            Worker worker = sch.createWorker();
+
+            Disposable d = worker.schedule(() -> { }, 1, TimeUnit.SECONDS);
+
+            d.dispose();
+
+            int i = 150;
+
+            while (i-- > 0) {
+                assertFalse("Task interrupt detected", exec.interruptReceived.get());
+                Thread.sleep(10);
+            }
+
+        } finally {
+            exec.shutdownNow();
+        }
+    }
+
+    @Test
+    public void hasInterruptBeforeRunningDelayedWorker() throws Throwable {
+        TrackInterruptScheduledExecutor exec = new TrackInterruptScheduledExecutor();
+
+        try {
+            Scheduler sch = Schedulers.from(exec, true);
+
+            Worker worker = sch.createWorker();
+
+            Disposable d = worker.schedule(() -> { }, 1, TimeUnit.SECONDS);
+
+            d.dispose();
+
+            Thread.sleep(100);
+            assertTrue("Task interrupt detected", exec.interruptReceived.get());
+
+        } finally {
+            exec.shutdownNow();
+        }
+    }
+
+    @Test
+    public void noInterruptAfterRunningDelayedWorker() throws Throwable {
+        TrackInterruptScheduledExecutor exec = new TrackInterruptScheduledExecutor();
+
+        try {
+            Scheduler sch = Schedulers.from(exec, false);
+
+            Worker worker = sch.createWorker();
+            AtomicBoolean taskRun = new AtomicBoolean();
+
+            Disposable d = worker.schedule(() -> {
+                taskRun.set(true);
+                try {
+                    Thread.sleep(1000);
+                } catch (InterruptedException ex) {
+                    exec.interruptReceived.set(true);
+                }
+            }, 100, TimeUnit.MILLISECONDS);
+
+            Thread.sleep(150);
+            ;
+            d.dispose();
+
+            int i = 50;
+
+            while (i-- > 0) {
+                assertFalse("Task interrupt detected", exec.interruptReceived.get());
+                Thread.sleep(10);
+            }
+
+            assertTrue("Task run at all", taskRun.get());
+
+        } finally {
+            exec.shutdownNow();
+        }
+    }
 }
diff --git a/src/test/java/io/reactivex/rxjava3/subjects/ReplaySubjectTest.java b/src/test/java/io/reactivex/rxjava3/subjects/ReplaySubjectTest.java
index e752278b2fd..8417b530819 100644
--- a/src/test/java/io/reactivex/rxjava3/subjects/ReplaySubjectTest.java
+++ b/src/test/java/io/reactivex/rxjava3/subjects/ReplaySubjectTest.java
@@ -1378,4 +1378,70 @@ public void timeAndSizeRemoveCorrectNumberOfOld() {
 
         rs.test().assertValuesOnly(4, 5);
     }
+
+    @Test
+    public void terminationSubscriptionRaceUnbounded() throws Throwable {
+        for (int i = 1; i <= 10000; i++) {
+            Subject source = ReplaySubject.create();
+            Subject sink = PublishSubject.create();
+            TestObserver observer = sink.test();
+            Schedulers.computation().scheduleDirect(() -> {
+                // issue signals to the source in adherence to the reactive streams specification
+                source.onSubscribe(Disposable.empty());
+                source.onNext("hello");
+                source.onNext("world");
+                source.onComplete();
+            });
+            Schedulers.computation().scheduleDirect(() -> {
+                // connect the source to the sink in parallel with the signals issued to the source
+                // note the cast() operator, which is here to detect non-String escapees
+                source.cast(String.class).subscribe(sink);
+            });
+            observer.await().assertValues("hello", "world").assertComplete();
+        }
+    }
+
+    @Test
+    public void terminationSubscriptionRaceSizeBound() throws Throwable {
+        for (int i = 1; i <= 10000; i++) {
+            Subject source = ReplaySubject.createWithSize(20);
+            Subject sink = PublishSubject.create();
+            TestObserver observer = sink.test();
+            Schedulers.computation().scheduleDirect(() -> {
+                // issue signals to the source in adherence to the reactive streams specification
+                source.onSubscribe(Disposable.empty());
+                source.onNext("hello");
+                source.onNext("world");
+                source.onComplete();
+            });
+            Schedulers.computation().scheduleDirect(() -> {
+                // connect the source to the sink in parallel with the signals issued to the source
+                // note the cast() operator, which is here to detect non-String escapees
+                source.cast(String.class).subscribe(sink);
+            });
+            observer.await().assertValues("hello", "world").assertComplete();
+        }
+    }
+
+    @Test
+    public void terminationSubscriptionRaceTimeBound() throws Throwable {
+        for (int i = 1; i <= 10000; i++) {
+            Subject source = ReplaySubject.createWithTime(20, TimeUnit.MINUTES, Schedulers.computation());
+            Subject sink = PublishSubject.create();
+            TestObserver observer = sink.test();
+            Schedulers.computation().scheduleDirect(() -> {
+                // issue signals to the source in adherence to the reactive streams specification
+                source.onSubscribe(Disposable.empty());
+                source.onNext("hello");
+                source.onNext("world");
+                source.onComplete();
+            });
+            Schedulers.computation().scheduleDirect(() -> {
+                // connect the source to the sink in parallel with the signals issued to the source
+                // note the cast() operator, which is here to detect non-String escapees
+                source.cast(String.class).subscribe(sink);
+            });
+            observer.await().assertValues("hello", "world").assertComplete();
+        }
+    }
 }
diff --git a/src/test/java/io/reactivex/rxjava3/testsupport/TestHelper.java b/src/test/java/io/reactivex/rxjava3/testsupport/TestHelper.java
index 362b1d165a6..d38ad8f9985 100644
--- a/src/test/java/io/reactivex/rxjava3/testsupport/TestHelper.java
+++ b/src/test/java/io/reactivex/rxjava3/testsupport/TestHelper.java
@@ -2440,23 +2440,16 @@ public static void assertCompositeExceptions(TestSubscriberEx ts, Class ts, Object... classes) {
+    public static void assertCompositeExceptions(TestSubscriberEx ts, Object... classesAndMessages) {
         ts
         .assertSubscribed()
         .assertError(CompositeException.class)
         .assertNotComplete();
 
-        List list = compositeList(ts.errors().get(0));
-
-        assertEquals(classes.length, list.size());
-
-        for (int i = 0; i < classes.length; i += 2) {
-            assertError(list, i, (Class)classes[i], (String)classes[i + 1]);
-        }
+        assertCompositeExceptionListOf(ts.errors().get(0), classesAndMessages);
     }
 
     /**
@@ -2485,22 +2478,26 @@ public static void assertCompositeExceptions(TestObserverEx to, Class to, Object... classes) {
+    public static void assertCompositeExceptions(TestObserverEx to, Object... classesAndMessages) {
         to
         .assertSubscribed()
         .assertError(CompositeException.class)
         .assertNotComplete();
 
-        List list = compositeList(to.errors().get(0));
+        assertCompositeExceptionListOf(to.errors().get(0), classesAndMessages);
+    }
 
-        assertEquals(classes.length, list.size());
+    @SuppressWarnings("unchecked")
+    static void assertCompositeExceptionListOf(Throwable ex, Object... classesAndMessages) {
+        List list = compositeList(ex);
+
+        assertEquals(classesAndMessages.length, 2 * list.size());
 
-        for (int i = 0; i < classes.length; i += 2) {
-            assertError(list, i, (Class)classes[i], (String)classes[i + 1]);
+        for (int i = 0; i < list.size(); i++) {
+            assertError(list, i, (Class)classesAndMessages[2 * i], (String)classesAndMessages[2 * i + 1]);
         }
     }
 
diff --git a/src/test/java/io/reactivex/rxjava3/validators/NonNullMethodTypeArgumentCheck.java b/src/test/java/io/reactivex/rxjava3/validators/NonNullMethodTypeArgumentCheck.java
index f0abb5b23e8..e8c4b81715e 100644
--- a/src/test/java/io/reactivex/rxjava3/validators/NonNullMethodTypeArgumentCheck.java
+++ b/src/test/java/io/reactivex/rxjava3/validators/NonNullMethodTypeArgumentCheck.java
@@ -57,10 +57,12 @@ static void process(Class clazz) {
 
                             for (String ta : parseTypeArguments(line)) {
                                 if (!ta.startsWith("@NonNull") && !ta.startsWith("@Nullable")) {
-                                    result.append("Missing annotation on argument ").append(ta).append("\r\nat ")
-                                    .append(parentPackage).append(".").append(className).append(".method(")
-                                    .append(className).append(".java:").append(lineCount).append(")\r\n");
-                                    count++;
+                                    if (!("Maybe".equals(clazz.getSimpleName()) && (line.contains("fromCallable(") || line.contains("fromSupplier(")))) {
+                                        result.append("Missing annotation on argument ").append(ta).append("\r\nat ")
+                                        .append(parentPackage).append(".").append(className).append(".method(")
+                                        .append(className).append(".java:").append(lineCount).append(")\r\n");
+                                        count++;
+                                    }
                                 }
                             }
                         }
diff --git a/src/test/java/io/reactivex/rxjava3/validators/ParamValidationCheckerTest.java b/src/test/java/io/reactivex/rxjava3/validators/ParamValidationCheckerTest.java
index 51c7626ed54..c2ca87d4d2d 100644
--- a/src/test/java/io/reactivex/rxjava3/validators/ParamValidationCheckerTest.java
+++ b/src/test/java/io/reactivex/rxjava3/validators/ParamValidationCheckerTest.java
@@ -149,9 +149,11 @@ public void checkParallelFlowable() {
         // negative time is considered as zero time
         addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "debounce", Long.TYPE, TimeUnit.class));
         addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "debounce", Long.TYPE, TimeUnit.class, Scheduler.class));
+        addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "debounce", Long.TYPE, TimeUnit.class, Scheduler.class, Consumer.class));
 
         // null Action allowed
         addOverride(new ParamOverride(Flowable.class, 1, ParamMode.ANY, "onBackpressureBuffer", Long.TYPE, Action.class, BackpressureOverflowStrategy.class));
+        addOverride(new ParamOverride(Flowable.class, 1, ParamMode.ANY, "onBackpressureBuffer", Long.TYPE, Action.class, BackpressureOverflowStrategy.class, Consumer.class));
 
         // zero repeat is allowed
         addOverride(new ParamOverride(Flowable.class, 0, ParamMode.NON_NEGATIVE, "repeat", Long.TYPE));
@@ -177,6 +179,7 @@ public void checkParallelFlowable() {
         // negative time is considered as zero time
         addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "throttleWithTimeout", Long.TYPE, TimeUnit.class));
         addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "throttleWithTimeout", Long.TYPE, TimeUnit.class, Scheduler.class));
+        addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "throttleWithTimeout", Long.TYPE, TimeUnit.class, Scheduler.class, Consumer.class));
 
         // negative time is considered as zero time
         addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "take", Long.TYPE, TimeUnit.class));
@@ -190,6 +193,7 @@ public void checkParallelFlowable() {
         addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "sample", Long.TYPE, TimeUnit.class, Boolean.TYPE));
         addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "sample", Long.TYPE, TimeUnit.class, Scheduler.class));
         addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "sample", Long.TYPE, TimeUnit.class, Scheduler.class, Boolean.TYPE));
+        addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "sample", Long.TYPE, TimeUnit.class, Scheduler.class, Boolean.TYPE, Consumer.class));
 
         // negative time is considered as zero time
         addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "takeLast", Long.TYPE, TimeUnit.class));
@@ -220,16 +224,19 @@ public void checkParallelFlowable() {
         // negative time is considered as zero time
         addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "throttleFirst", Long.TYPE, TimeUnit.class));
         addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "throttleFirst", Long.TYPE, TimeUnit.class, Scheduler.class));
+        addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "throttleFirst", Long.TYPE, TimeUnit.class, Scheduler.class, Consumer.class));
 
         // negative time is considered as zero time
         addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "throttleLast", Long.TYPE, TimeUnit.class));
         addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "throttleLast", Long.TYPE, TimeUnit.class, Scheduler.class));
+        addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "throttleLast", Long.TYPE, TimeUnit.class, Scheduler.class, Consumer.class));
 
         // negative time is considered as zero time
         addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "throttleLatest", Long.TYPE, TimeUnit.class));
         addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "throttleLatest", Long.TYPE, TimeUnit.class, Scheduler.class));
         addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "throttleLatest", Long.TYPE, TimeUnit.class, Boolean.TYPE));
         addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "throttleLatest", Long.TYPE, TimeUnit.class, Scheduler.class, Boolean.TYPE));
+        addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "throttleLatest", Long.TYPE, TimeUnit.class, Scheduler.class, Boolean.TYPE, Consumer.class));
 
         // negative buffer time is considered as zero buffer time
         addOverride(new ParamOverride(Flowable.class, 0, ParamMode.ANY, "window", Long.TYPE, TimeUnit.class));
@@ -396,6 +403,7 @@ public void checkParallelFlowable() {
         // negative time is considered as zero time
         addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "debounce", Long.TYPE, TimeUnit.class));
         addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "debounce", Long.TYPE, TimeUnit.class, Scheduler.class));
+        addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "debounce", Long.TYPE, TimeUnit.class, Scheduler.class, Consumer.class));
 
         // zero repeat is allowed
         addOverride(new ParamOverride(Observable.class, 0, ParamMode.NON_NEGATIVE, "repeat", Long.TYPE));
@@ -421,6 +429,7 @@ public void checkParallelFlowable() {
         // negative time is considered as zero time
         addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "throttleWithTimeout", Long.TYPE, TimeUnit.class));
         addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "throttleWithTimeout", Long.TYPE, TimeUnit.class, Scheduler.class));
+        addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "throttleWithTimeout", Long.TYPE, TimeUnit.class, Scheduler.class, Consumer.class));
 
         // negative time is considered as zero time
         addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "take", Long.TYPE, TimeUnit.class));
@@ -434,6 +443,7 @@ public void checkParallelFlowable() {
         addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "sample", Long.TYPE, TimeUnit.class, Boolean.TYPE));
         addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "sample", Long.TYPE, TimeUnit.class, Scheduler.class));
         addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "sample", Long.TYPE, TimeUnit.class, Scheduler.class, Boolean.TYPE));
+        addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "sample", Long.TYPE, TimeUnit.class, Scheduler.class, Boolean.TYPE, Consumer.class));
 
         // negative time is considered as zero time
         addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "takeLast", Long.TYPE, TimeUnit.class));
@@ -464,16 +474,19 @@ public void checkParallelFlowable() {
         // negative time is considered as zero time
         addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "throttleFirst", Long.TYPE, TimeUnit.class));
         addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "throttleFirst", Long.TYPE, TimeUnit.class, Scheduler.class));
+        addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "throttleFirst", Long.TYPE, TimeUnit.class, Scheduler.class, Consumer.class));
 
         // negative time is considered as zero time
         addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "throttleLast", Long.TYPE, TimeUnit.class));
         addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "throttleLast", Long.TYPE, TimeUnit.class, Scheduler.class));
+        addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "throttleLast", Long.TYPE, TimeUnit.class, Scheduler.class, Consumer.class));
 
         // negative time is considered as zero time
         addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "throttleLatest", Long.TYPE, TimeUnit.class));
         addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "throttleLatest", Long.TYPE, TimeUnit.class, Scheduler.class));
         addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "throttleLatest", Long.TYPE, TimeUnit.class, Boolean.TYPE));
         addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "throttleLatest", Long.TYPE, TimeUnit.class, Scheduler.class, Boolean.TYPE));
+        addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "throttleLatest", Long.TYPE, TimeUnit.class, Scheduler.class, Boolean.TYPE, Consumer.class));
 
         // negative buffer time is considered as zero buffer time
         addOverride(new ParamOverride(Observable.class, 0, ParamMode.ANY, "window", Long.TYPE, TimeUnit.class));
@@ -560,6 +573,7 @@ public void checkParallelFlowable() {
         for (Class interfaces : AllFunctionals.class.getInterfaces()) {
             defaultValues.put(interfaces, af);
         }
+        defaultValues.put(Subscriber.class, af);
         defaultValues.put(TimeUnit.class, TimeUnit.SECONDS);
         defaultValues.put(Scheduler.class, Schedulers.single());
         defaultValues.put(BackpressureStrategy.class, BackpressureStrategy.MISSING);
@@ -926,7 +940,7 @@ static final class AllFunctionals
     Function3, Function4, Function5, Function6, Function7, Function8, Function9,
     FlowableOnSubscribe, ObservableOnSubscribe, SingleOnSubscribe, MaybeOnSubscribe, CompletableOnSubscribe,
     FlowableTransformer, ObservableTransformer, SingleTransformer, MaybeTransformer, CompletableTransformer,
-    Subscriber, FlowableSubscriber, Observer, SingleObserver, MaybeObserver, CompletableObserver,
+    FlowableSubscriber, Observer, SingleObserver, MaybeObserver, CompletableObserver,
     FlowableOperator, ObservableOperator, SingleOperator, MaybeOperator, CompletableOperator,
     Comparator, ParallelTransformer
     {
@@ -1211,4 +1225,4 @@ public String toString() {
             return "NeverCompletable";
         }
     }
-}
+}
\ No newline at end of file