Repository navigation
Add diagnostics_channel TracingChannel support - #20
Closed
MiichelleZhou wants to merge 7 commits into
Closed
MiichelleZhou wants to merge 7 commits into
MiichelleZhou wants to merge 7 commits into
Conversation
Enables instrumentation libraries (OpenTelemetry, etc.) to subscribe to structured events without monkey-patching. Uses TracingChannel for async context propagation and plain channels for simple events. Channels: - pg:query (TracingChannel) — query lifecycle with result enrichment - pg:connection (TracingChannel) — client connect lifecycle - pg:pool:connect (TracingChannel) — pool checkout lifecycle - pg:pool:release (plain) — client released back to pool - pg:pool:remove (plain) — client removed from pool All instrumentation is guarded by hasSubscribers for zero overhead when unused. Gracefully degrades to no-ops on Node < 19.9 or non-Node environments. Closes #3619 Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
TracingChannel is not available on Node 18 LTS. Skip the tracing-dependent tests gracefully instead of failing. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Node 18 backported TracingChannel but without the aggregated `hasSubscribers` getter (it returns `undefined` instead of a boolean). Raw truthiness checks treat `undefined` as "no subscribers" which silently disables tracing on Node 18. Replace all `channel.hasSubscribers` guards with `shouldTrace(channel)` which checks `hasSubscribers !== false` — treating `undefined` (Node 18) as "might have subscribers, trace unconditionally" and `false` (Node 20+) as "definitely no subscribers, skip". Also removes the now-unnecessary test skip logic since TracingChannel does exist on Node 18. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Node 18 backported TracingChannel but with a buggy implementation — unsubscribing and resubscribing to the same channel crashes internally (`_subscribers` becomes undefined). Node 16 has no TracingChannel at all. Gate tests on `hasStableTracingChannel` which checks both that `dc.tracingChannel` exists AND that the aggregated `hasSubscribers` getter returns a boolean (only true on Node 19.9+/20.5+). TracingChannel tests: skipped on Node 16/18, run on Node 20+ Plain channel tests (release/remove): run on all versions Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
…omise type tracePromise wraps the result in a native Promise, which breaks clients configured with a custom Promise implementation (e.g. bluebird). Switch to traceCallback inside the user's this._Promise constructor so the returned promise type is always correct. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
There was a problem hiding this comment.
Copilot review overview
🟡 Changes recommended
The published pool package is currently broken, and several query and context-propagation paths are incomplete.
Get a fresh assessment by requesting another Copilot review.
Review tier: Balanced
Findings: 1
Open findings (7)
What changed in this PR
Adds diagnostics_channel tracing for PostgreSQL queries, connections, and pool lifecycle operations.
Changes:
- Adds guarded diagnostics channel definitions.
- Instruments client and pool operations.
- Adds lifecycle event tests.
| File | Description |
|---|---|
packages/pg/lib/diagnostics.js |
Defines client tracing channels. |
packages/pg/lib/client.js |
Traces connections and queries. |
packages/pg/test/unit/client/diagnostics-tests.js |
Tests client diagnostics. |
packages/pg-pool/diagnostics.js |
Defines pool diagnostics channels. |
packages/pg-pool/index.js |
Instruments pool lifecycle operations. |
packages/pg-pool/test/diagnostics.js |
Tests pool diagnostics. |
💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.
| @@ -1,5 +1,6 @@ | |||
| 'use strict' | |||
| const EventEmitter = require('events').EventEmitter | |||
| const { poolConnectChannel, poolReleaseChannel, poolRemoveChannel, shouldTrace } = require('./diagnostics') | |||
Comment on lines
+218
to
+221
| poolConnectChannel.traceCallback( | ||
| (tracedCb) => { | ||
| response.callback = tracedCb | ||
| }, |
| const defaults = require('./defaults') | ||
| const Connection = require('./connection') | ||
| const crypto = require('./crypto/utils') | ||
| const { queryChannel, connectionChannel, shouldTrace } = require('./diagnostics') |
| } | ||
| const origCb = query.callback | ||
| const enrichedCb = (err, res) => { | ||
| if (res) context.result = { rowCount: res.rowCount, command: res.command } |
| } | ||
| queryChannel.traceCallback( | ||
| (tracedCb) => { | ||
| query.callback = tracedCb |
Comment on lines
+31
to
+33
| function shouldTrace(channel) { | ||
| return channel.hasSubscribers !== false | ||
| } |
Comment on lines
+27
to
+29
| function shouldTrace(channel) { | ||
| return channel.hasSubscribers !== false | ||
| } |
MiichelleZhou
deleted the
eval/3650/ccr-balanced/2026-09-14.2/round-2
branch
September 14, 2026 22:05
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
This PR introduces tracing channels support to
pg-poolandpgquerying methods as discussed in #3619I haven't yet run a benchmark, but without active tracing or subscribers the overhead is non-existent so existing users shouldn't be affected. The overhead would come from the consumers of the diag channels published here which is done anyways via monkey patching.
I added the following channels:
pg:querypgpg:connectionpgpg:pool:connectpg-poolpg:pool:releasepg-poolpg:pool:removepg-poolI understand there may be hesitation given that AI tooling was used in the implementation. To be clear, this isn't a drive-by contribution. I designed the channel layout, wrote the proposal document, and iterated through multiple rounds to handle real edge cases (Node 18 compat, preserving custom Promise types, hasSubscribers guards). The AI assisted with the code, but the approach and decisions are mine.
Usage
Instrumentations will only need to subscribe to tracing channels to create traces, logs or metrics:
This is part of a broader initiative to bring TracingChannel support to the most widely used Node.js database and cache libraries. The same pattern has already been merged and shipped in:
I have been directly involved in those prior implementations and I'm happy to own this through to release, address any feedback, and provide whatever support is needed. Would love to hear your thoughts.
Supersedes #3624.