[Dataflow Streaming Java] Fix possible IllegalStateException when grpc streams have deadline exceeded.

[scwhittle]

Example error that could be observed previously when onComplete was called on ResettableThrowingStreamObserver which already called delegate.onError within onNext.

{
  "jsonPayload": {
    "exception": "java.lang.IllegalStateException\n    at com.google.common.base.Preconditions.checkState(Preconditions.java:527)\n    at org.apache.beam.runners.dataflow.worker.windmill.client.grpc.observers.DirectStreamObserver.onCompleted(DirectStreamObserver.java:198)\n    at org.apache.beam.runners.dataflow.worker.windmill.client.ResettableThrowingStreamObserver.onCompleted(ResettableThrowingStreamObserver.java:143)\n    at org.apache.beam.runners.dataflow.worker.windmill.client.AbstractWindmillStream.halfClose(AbstractWindmillStream.java:450)\n    at org.apache.beam.runners.dataflow.worker.windmill.client.WindmillStreamPool.getStream(WindmillStreamPool.java:131)\n    at org.apache.beam.runners.dataflow.worker.windmill.client.WindmillStreamPool.getCloseableStream(WindmillStreamPool.java:137)\n    at org.apache.beam.runners.dataflow.worker.windmill.client.commits.StreamingEngineWorkCommitter.streamingCommitLoop(StreamingEngineWorkCommitter.java:178)\n    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)\n    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)\n    at java.base/java.lang.Thread.run(Thread.java:1583)",
    "job": "2025-09-12_13_56_55-8555386915480239630",
    "logger": "org.apache.beam.runners.dataflow.worker.windmill.client.grpc.GrpcCommitWorkStream",
    "message": "Unexpected error when trying to close stream",
    "thread": "49",
  }
}

---

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[scwhittle]

R: @arunpandianp

[gemini-code-assist]

Summary of Changes

Hello @scwhittle, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves a critical IllegalStateException that could occur in Dataflow Streaming Java jobs when gRPC streams encountered deadline exceeded errors. The core issue stemmed from improper state management within ResettableThrowingStreamObserver and DirectStreamObserver, leading to onComplete being called after onError had already been processed. The changes introduce more robust state tracking and error handling logic, ensuring that stream observers correctly manage their lifecycle and prevent redundant or out-of-order termination calls, thereby improving the stability of streaming data processing.

Highlights

• Stream Observer State Management: Modified ResettableThrowingStreamObserver to prevent IllegalStateException by ensuring isCurrentStreamClosed is correctly updated and onError is not invoked on an already closed stream, particularly when handling StreamObserverCancelledException.
• Robust Stream Closure: Wrapped onError and onCompleted calls in ResettableThrowingStreamObserver with try-finally blocks to guarantee that the isCurrentStreamClosed flag is always set, even if the delegate observer throws an exception.
• Outbound Observer Error Sequencing: Adjusted the onError method in DirectStreamObserver to set the isOutboundObserverClosed flag before calling the outboundObserver.onError method, preventing potential race conditions or re-entry issues.
• Exception Visibility: Made the constructors for StreamObserverCancelledException public, likely to facilitate broader usage or testing of this specific exception type.
• Enhanced Test Coverage: Added new unit tests to ResettableThrowingStreamObserverTest to cover basic onNext, onError, and onCompleted scenarios, as well as specific cases involving StreamObserverCancelledException during onNext processing.

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[github-actions]

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[scwhittle]

/gemini review

[gemini-code-assist]

Code Review

This pull request effectively addresses a potential IllegalStateException in gRPC streams by improving the state management in ResettableThrowingStreamObserver under concurrent access. The core fix correctly handles stream closure when onNext fails, preventing race conditions with subsequent onCompleted or onError calls. The use of try-finally blocks in onError and onCompleted and the state update ordering change in DirectStreamObserver are excellent defensive programming practices that enhance robustness. The new tests provide good coverage for the fix. I have one suggestion to refactor the new tests for better maintainability.

[arunpandianp]

this is under the mutex now, is it expected?

[scwhittle]

I was doing it to be consistent with onError synchronization but I will change back since if we want to CP then it seems a riskier change.

[arunpandianp]

Thansk, sounds good.

[scwhittle]

Run Java PreCommit

[Abacn]

Not sure if related but GrpcGetDataStreamTest appears to be increasingly flaky: #36347 also observed in Beam import and repro'd locally

update: The symptom remains the same after reverting this PR locally and run tests