Threading refactor (8/8): reuse user-configured executor for user-callback dispatch#8
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ShimImpl now sources the userCallbackExecutor from the StubSettings when the caller has configured one — either via InstantiatingGrpcChannelProvider's setExecutor (PR googleapis#13557 exposed the getter on TransportChannelProvider) or the legacy StubSettings#setExecutorProvider. Ownership follows the source: transport-set is borrowed by convention; the legacy ExecutorProvider honors shouldAutoClose(). When neither is set the existing behavior is preserved — ShimImpl owns a dedicated bigtable-callback-shim cached pool. Client.userCallbackExecutor widens from Resource<ExecutorService> to Resource<Executor> to accept the borrowed handle; downstream consumers already require only Executor. The standalone Client.create(ClientSettings) path is unchanged: ClientSettings carries no executor wiring to source from.
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Summary
Phase 8 of 8. When the caller configures an executor on their
StubSettingsorInstantiatingGrpcChannelProvider, reuse it for user-callback dispatch instead of always allocating a separatebigtable-callback-shimcached pool. Closes the TODO atClient.java:92-94that had been blocked on a missing gax API (now landed via googleapis/google-cloud-java#13557).What's in here
refactor: reuse user-configured executor for user-callback dispatchShimImpl.createnow picks the user-callback executor via a newselectUserCallbackExecutor(transportProvider, executorProvider)helper. Priority: transport-set executor (InstantiatingGrpcChannelProvider#getExecutor, exposed by gax PR googleapis#13557) → legacyStubSettings#getExecutorProvider→ fresh cached pool. Ownership follows the source: transport-set is borrowed (Resource.createShared); legacy honorsExecutorProvider#shouldAutoClose(); the fallback cached pool is owned byClientas before.Client.userCallbackExecutorwidens fromResource<ExecutorService>toResource<Executor>to accept the borrowed handle.Detection signals
Both are crisp without class-identity checks:
transportProvider.getExecutor() != null→ user calledsetExecutoron the channel provider.stubSettings.getExecutorProvider() != null→ user called the deprecatedsetExecutorProvider(gax tracks this viadeprecatedExecutorProviderSetinStubSettings.java:139-141, returningnullfromgetExecutorProvider()otherwise).Tests
ShimImplTest(new) covers all four branches ofselectUserCallbackExecutor: transport-set, legacy withshouldAutoClose=false, legacy withshouldAutoClose=true, and the fallback owned pool (asserts thread-name prefix and thatclose()shuts it down).The standalone
Client.create(ClientSettings)path is unchanged —ClientSettingscarries no executor wiring to source from.Stack position
threading-refactor-phase-7