Add opt-in text log pattern injection for Logback and Log4j by lrwh · Pull Request #21261 · open-telemetry/opentelemetry-java-instrumentation

lrwh · 2026-11-09T03:09:38Z

Add opt-in correlation fields to existing Logback and Log4j text patterns so console and file logs can be correlated without editing each application's logging configuration.

otel.instrumentation.logging.pattern-injection.enabled=true

Disabled by default. Supports Logback classic 1.0+, Log4j 1.2, and Log4j2 2.7+. Reuses existing MDC converters and configured trace/span key names, preserves timestamp options and repeated layout initialization, and exposes the resource's service.name outside a span. Application-provided correlation values take precedence. JSON layouts and Log4j2 PatternSelector branches are excluded.

Closes #21260.

Validated the parser and baseline/latest-dependency check tasks for all five logging modules on JDK 25, including focused parser and Logback checks for native default-key semantics. On Java 8, 102 installed-agent tests pass; six cases requiring newer Logback color converters are skipped. Regression coverage includes whole-line wrappers, literal braces in Logback composites, version-specific MDC defaults, native escaped keys, special correlation keys, key lists and wrapper aliases, repeated initialization, and original-MDC export with pattern injection enabled.

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Copilot

🟡 Changes recommended

Log-pattern handling can place Log4j2 correlation fields on the wrong line, omit Logback trace IDs for comma-containing keys, and duplicate correlation fields inside Log4j2 color wrappers.

3 open issues

Encode custom Logback keys with commas · New
Recognize Log4j2 color wrappers around MDC converters · New
Restrict composite-pattern scanning to Logback · New

What changed in this PR

Adds opt-in text log correlation to the Java agent’s existing Logback and Log4j instrumentation, addressing #21260 without requiring application logging-pattern changes.

Changes:

Adds a shared pattern rewriter and framework-specific layout instrumentation, disabled by default.
Exposes service.name outside spans and preserves application-provided correlation values.
Adds parser and installed-agent tests, configuration metadata, and usage documentation.

File	Description
`javaagent-extension-api/src/test/java/io/opentelemetry/javaagent/bootstrap/internal/LogPatternInjectionTest.java`	Tests pattern parsing and repeated enhancement.
`javaagent-extension-api/src/main/java/io/opentelemetry/javaagent/bootstrap/internal/LogPatternInjection.java`	Adds shared configuration and pattern rewriting.
`javaagent-extension-api/src/main/java/io/opentelemetry/javaagent/bootstrap/internal/ConfiguredResourceAttributesHolder.java`	Exposes service name when injection is enabled.
`instrumentation/logback/logback-mdc-1.0/metadata.yaml`	References the shared setting.
`instrumentation/logback/logback-mdc-1.0/javaagent/src/test/java/io/opentelemetry/javaagent/instrumentation/logback/v1_0/LogPatternTest.java`	Tests Logback rendering and application overrides.
`instrumentation/logback/logback-mdc-1.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/logback/mdc/v1_0/PatternLayoutInstrumentation.java`	Enhances Logback patterns during startup.
`instrumentation/logback/logback-mdc-1.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/logback/mdc/v1_0/LoggingEventInstrumentation.java`	Preserves existing MDC values during enrichment.
`instrumentation/logback/logback-mdc-1.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/logback/mdc/v1_0/LogbackMdcInstrumentationModule.java`	Registers layout instrumentation.
`instrumentation/logback/logback-mdc-1.0/javaagent/README.md`	Documents the opt-in setting.
`instrumentation/logback/logback-mdc-1.0/javaagent/build.gradle.kts`	Adds injection and custom-key test variants.
`instrumentation/log4j/log4j-mdc-1.2/metadata.yaml`	References the shared setting.
`instrumentation/log4j/log4j-mdc-1.2/javaagent/src/test/java/io/opentelemetry/javaagent/instrumentation/log4j/mdc/v1_2/LogPatternTest.java`	Tests Log4j 1 rendering and repeated initialization.
`instrumentation/log4j/log4j-mdc-1.2/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/log4j/mdc/v1_2/PatternLayoutInstrumentation.java`	Enhances constructor and setter patterns.
`instrumentation/log4j/log4j-mdc-1.2/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/log4j/mdc/v1_2/LoggingEventInstrumentation.java`	Enriches whole-MDC properties when enabled.
`instrumentation/log4j/log4j-mdc-1.2/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/log4j/mdc/v1_2/Log4j1PatternInjection.java`	Detects native whole-MDC converter support.
`instrumentation/log4j/log4j-mdc-1.2/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/log4j/mdc/v1_2/Log4j1InstrumentationModule.java`	Registers layout instrumentation.
`instrumentation/log4j/log4j-mdc-1.2/javaagent/README.md`	Documents the opt-in setting.
`instrumentation/log4j/log4j-mdc-1.2/javaagent/build.gradle.kts`	Adds injection and custom-key test variants.
`instrumentation/log4j/log4j-context-data/log4j-context-data-common/testing/src/main/java/io/opentelemetry/instrumentation/log4j/contextdata/LogPatternTest.java`	Shares Log4j2 rendering and selector-exclusion tests.
`instrumentation/log4j/log4j-context-data/log4j-context-data-common/testing/src/main/java/io/opentelemetry/instrumentation/log4j/contextdata/Log4j2Test.java`	Tests application-value precedence.
`instrumentation/log4j/log4j-context-data/log4j-context-data-2.7/metadata.yaml`	References the shared setting.
`instrumentation/log4j/log4j-context-data/log4j-context-data-2.7/javaagent/src/test/java/io/opentelemetry/javaagent/instrumentation/log4j/contextdata/v2_7/AutoLogPatternTest.java`	Runs shared tests with the installed agent.
`instrumentation/log4j/log4j-context-data/log4j-context-data-2.7/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/log4j/contextdata/v2_7/SpanDecoratingContextDataInjector.java`	Preserves application context-data values.
`instrumentation/log4j/log4j-context-data/log4j-context-data-2.7/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/log4j/contextdata/v2_7/PatternLayoutInstrumentation.java`	Enhances builder patterns without selectors.
`instrumentation/log4j/log4j-context-data/log4j-context-data-2.7/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/log4j/contextdata/v2_7/Log4j27InstrumentationModule.java`	Registers layout instrumentation.
`instrumentation/log4j/log4j-context-data/log4j-context-data-2.7/javaagent/build.gradle.kts`	Adds injection and custom-key test variants.
`instrumentation/log4j/log4j-context-data/log4j-context-data-2.17/metadata.yaml`	References the shared setting.
`instrumentation/log4j/log4j-context-data/log4j-context-data-2.17/library-autoconfigure/src/main/java/io/opentelemetry/instrumentation/log4j/contextdata/v2_17/OpenTelemetryContextDataProvider.java`	Preserves application ThreadContext values.
`instrumentation/log4j/log4j-context-data/log4j-context-data-2.17/javaagent/src/test/java/io/opentelemetry/javaagent/instrumentation/log4j/contextdata/v2_17/AutoLogPatternTest.java`	Runs shared tests with the installed agent.
`instrumentation/log4j/log4j-context-data/log4j-context-data-2.17/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/log4j/contextdata/v2_17/PatternLayoutInstrumentation.java`	Enhances builder patterns without selectors.
`instrumentation/log4j/log4j-context-data/log4j-context-data-2.17/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/log4j/contextdata/v2_17/Log4j2InstrumentationModule.java`	Registers layout instrumentation.
`instrumentation/log4j/log4j-context-data/log4j-context-data-2.17/javaagent/README.md`	Documents the opt-in setting.
`instrumentation/log4j/log4j-context-data/log4j-context-data-2.17/javaagent/build.gradle.kts`	Adds variants while retaining thread-local coverage.
`instrumentation-docs/src/main/resources/shared-config-definitions.yaml`	Defines shared configuration metadata.
`docs/logging-pattern-injection.md`	Explains setup, supported layouts, and limitations.

_{Review effort: Balanced}

Copilot

🟡 Changes recommended

Logback MDC keys containing commas and both quote characters are quoted without escaping embedded delimiters, preventing correlation-value lookup and duplicating fields on repeated initialization.

1 open issue

Escape quotes and backslashes in Logback MDC option keys · New

3 resolved since last review

_{Review effort: Balanced}

Copilot

🔵 Needs a closer look

Configured trace/span keys are inserted verbatim into Log4j labels and MDC options, allowing percent signs to split log records and commas to cause trace IDs to disappear.

No open issues 🎉

2 previously missed issues

In code that hasn't changed since last review

Handle commas in custom Log4j2 MDC keys

javaagent-extension-api/src/main/java/io/opentelemetry/javaagent/bootstrap/internal/LogPatternInjection.java:72

[Javaagent] Passing the configured key verbatim is unsafe for Log4j2 MDC options. A trace key such as custom,trace becomes %X{custom,trace}, which selects two MDC entries rather than the single custom,trace entry populated by the instrumentation; the trace ID therefore disappears from the injected output. Add a safe option/key-resolution mechanism for Log4j2, analogous to the Logback alias handling, and exercise a comma-containing key in the installed-agent rendering tests.

Escape percent signs in Log4j labels for custom trace keys

javaagent-extension-api/src/main/java/io/opentelemetry/javaagent/bootstrap/internal/LogPatternInjection.java:77

[Javaagent] A configured trace/span key containing %, such as trace%n, is copied verbatim into the Log4j label, where %n becomes an extra newline and splits the log record. Escape literal percent signs as %% in Log4j labels while retaining the original key inside the MDC option. Add a rendering regression test for these custom keys.

1 resolved since last review

Escape quotes and backslashes in Logback MDC option keys

_{Review effort: Balanced}

Copilot

🔵 Needs a closer look

Human assessment is needed because framework-specific parsing, escaping, and wrapper handling can omit correlation fields or break log-record boundaries.

No open issues 🎉

_{Review effort: Balanced}

Copilot

🟡 Changes recommended

Pattern parsing can place correlation fields after newlines and misidentify Logback MDC keys, producing malformed log output and missing or duplicate trace IDs.

4 open issues

_{Review effort: Balanced}

+    return pattern.substring(0, end)
+        + " "
+        + fields


+          if ((option.equals(key) && (framework != Framework.LOG4J2 || option.indexOf(',') <= 0))
+              || (framework == Framework.LOGBACK && option.startsWith(key + ":-"))
+              || (framework == Framework.LOGBACK && option.isEmpty())) {


+        if (options.charAt(i) == '\\') {
+          i++;
+        } else if (options.charAt(i) == quote) {
+          return options.substring(1, i);


+      } else if (framework == Framework.LOGBACK && open == '(' && c == '{') {
+        i = logbackOptionEnd(pattern, i) - 1;


…ults

Add opt-in text log pattern correlation for Logback and Log4j

918f690

lrwh requested a review from a team as a code owner November 9, 2026 03:09

opentelemetry-pr-dashboard Bot requested a balanced review from Copilot November 9, 2026 03:10

opentelemetry-pr-dashboard Bot mentioned this pull request Nov 9, 2026

Pull Request Dashboard #18435

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Copilot started reviewing on behalf of lrwh November 9, 2026 03:11

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Fix log pattern quoting and Log4j2 parsing

399d801

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Comment thread ...ion-api/src/main/java/io/opentelemetry/javaagent/bootstrap/internal/LogPatternInjection.java Resolved

Handle special Logback MDC keys at converter initialization

b76afa9

opentelemetry-pr-dashboard Bot requested a balanced review from Copilot November 9, 2026 07:09

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Preserve special Log4j2 correlation keys in text patterns

34eb78e

opentelemetry-pr-dashboard Bot requested a balanced review from Copilot November 9, 2026 08:33

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lrwh added 2 commits November 10, 2026 09:11

Honor native MDC options and Log4j pattern aliases

431f02e

Merge main and preserve original Logback MDC export

9520f1c

opentelemetry-pr-dashboard Bot requested a balanced review from Copilot November 10, 2026 01:40

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Keep log correlation within wrapped records and honor native MDC defa…

d46a7c9

…ults

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Add opt-in text log pattern injection for Logback and Log4j - #21261

Add opt-in text log pattern injection for Logback and Log4j#21261
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		} else if (framework == Framework.LOGBACK && open == '(' && c == '{') {
		i = logbackOptionEnd(pattern, i) - 1;

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