feat: Add support for JFR contextual information

[marschall]

Description:

Feature addition
Annotate the operationName and traceID event fields with contextual so it shows up when using jfr print.

Existing Issue(s):

#2057

Testing:

Existing unit tests extended.

Documentation:

Attribute documentation in readme updated.

Outstanding items:

See discussion in #2057

To avoid repetition in the presentation, it's probably best to annotate traceId only in a top-level event, such as the ScopeEvent or perhaps a new event that is even higher-level. SpanID is likely not that interesting either. If too much is annotated with @contextual, it will be hard for humans to parse.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: marschall / name: Philippe Marschall (f883cde)

[Copilot]

Pull request overview

This PR adds support for JFR contextual information by implementing the @Contextual meta-annotation for OpenTelemetry JFR events. This allows lower-level JVM/JDK events (like lock contention) to inherit trace and span context information when using tools like jfr print in JDK 25+. The implementation annotates the operationName field in SpanEvent and the traceId field in ScopeEvent (as a top-level event) to avoid information repetition.

Changes:

• Creates a @Contextual meta-annotation that mimics JDK 25's annotation without requiring JDK 25 compilation
• Annotates operationName in SpanEvent and traceId in ScopeEvent with @Contextual
• Extends unit tests to verify the presence of @Contextual annotations on these fields
• Updates README documentation to note which fields have the @Contextual annotation

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
jfr-events/src/main/java/io/opentelemetry/contrib/jfrevent/Contextual.java	New meta-annotation to support @Contextual for JFR contextual information
jfr-events/src/main/java/io/opentelemetry/contrib/jfrevent/SpanEvent.java	Annotates operationName field with @Contextual
jfr-events/src/main/java/io/opentelemetry/contrib/jfrevent/ScopeEvent.java	Annotates traceId field with @Contextual
jfr-events/src/test/java/io/opentelemetry/contrib/jfrevent/JfrSpanProcessorTest.java	Adds tests to verify @Contextual annotations are present on fields
jfr-events/README.md	Updates documentation to indicate which fields are @contextual; contains an incorrect field reference

[Copilot]

The test assertion only checks that the extracted list is not null, but does not validate that the @Contextual annotation is actually present on the field. The assertion should verify that the annotation is non-null, not just that the list exists. This could allow the test to pass even if the annotation is missing from the field.

Suggested change

	assertThat(events)
	.extracting(
	e ->
	e.getFields().stream()
	.filter(f -> f.getName().equals("operationName"))
	.map(d -> d.getAnnotation(Contextual.class))
	.collect(Collectors.toList()))
	assertThat(
	events.get(0).getFields().stream()
	.filter(f -> f.getName().equals("operationName"))
	.map(d -> d.getAnnotation(Contextual.class))
	.collect(Collectors.toList()))
	.singleElement()