core,opentelemetry: Fix server metric labels on early close

[becomeStar]

This addresses the server-side OpenTelemetry metric labeling bug from #12117 where a generated method can be recorded as grpc.method="other" if streamClosed() happens before serverCallStarted().

What changed

• add an internal StatsTraceContext.ServerCallMethodListener hook so tracers can consume an already-resolved primary-registry MethodDescriptor
• resolve the immutable internal primary registry on the transport path and seed method classification before the async MethodLookup path runs
• keep fallback registry lookup on the existing async path
• update the OpenTelemetry server tracer to use the early-resolved method classification for close metrics

Why this shape

• avoids tracer-side HandlerRegistry lookup
• uses only the immutable internal primary registry for early transport-path lookup
• keeps fallback registry lookup on the existing async path

Tests

• primary generated method: early close preserves the generated method name
• primary non-generated method: early close still records other
• fallback generated method: fallback lookup remains on the existing async path and does not introduce early transport-path classification
• tracer-level regression: serverCallMethodResolved() + streamClosed() records the generated method name without waiting for serverCallStarted()

Notes

• ServerCallMethodListener is an internal hook that carries the resolved MethodDescriptor; tracers consume the resolved result instead of performing registry lookup themselves
• ServerImpl uses InternalHandlerRegistry explicitly for the primary registry to make it clear that the early transport- path lookup is limited to the immutable internal primary registry
• this PR intentionally does not widen transport-path lookup to the fallback registry

Ref #12117

[kannanjgithub]

Unit test coverage is missing for non-generated method name case. If a method is not generated (or isSampledToLocalTracing is false), it should be recorded as "other". This applies to both the new serverCallMethodResolved() path and the standard serverCallStarted() path.

[becomeStar]

Thanks for the review.

Added the missing non-generated coverage in OpenTelemetryMetricsModuleTest.

The new tests cover both:

• the new serverCallMethodResolved() path
• the standard serverCallStarted() path

They verify that when isSampledToLocalTracing is false, the method is recorded as other for server metrics.

[Copilot]

Pull request overview

Fixes a server-side OpenTelemetry metrics labeling race where grpc.method could be recorded as "other" when streamClosed() occurs before serverCallStarted(), by propagating an early-resolved primary-registry MethodDescriptor to server tracers.

Changes:

• Add an internal StatsTraceContext.ServerCallMethodListener hook to deliver an already-resolved primary-registry MethodDescriptor before serverCallStarted().
• Resolve the immutable primary registry method on the transport path in ServerImpl and notify tracers early; keep fallback registry resolution on the existing async path.
• Update the OpenTelemetry server tracer and add regression tests covering early-close labeling for primary vs fallback and generated vs non-generated methods.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
core/src/main/java/io/grpc/internal/StatsTraceContext.java	Introduces ServerCallMethodListener and a notification method for early primary-registry method resolution.
core/src/main/java/io/grpc/internal/ServerImpl.java	Performs early primary-registry lookup on the transport path and notifies StatsTraceContext prior to async method lookup.
opentelemetry/src/main/java/io/grpc/opentelemetry/OpenTelemetryMetricsModule.java	Implements the new listener in the server tracer to seed method classification for close metrics.
core/src/test/java/io/grpc/internal/ServerImplTest.java	Adds transport-path/async-path tests validating labeling behavior across primary/fallback registries.
opentelemetry/src/test/java/io/grpc/opentelemetry/OpenTelemetryMetricsModuleTest.java	Adds tracer-level regression tests for method resolution preceding early stream close.

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[kannanjgithub]

/gcbrun