fix: wait for pending ACK callbacks in SolaceIO write finishBundle to prevent batch pipeline data loss [fj4WqyCCw3C5ShR1RfB7MoBPTpkRrBFYP1uT35g3MvT]

[waterWang]

Description

Fixes #39589

Problem: In batch pipelines, the SolaceIO write transform loses publish results because the pipeline finishes before asynchronous Solace ACK callbacks arrive. The @FinishBundle method calls publishResults() which drains the publishedResultsQueue, but the ACK callbacks that populate the queue haven't fired yet, so the queue is empty and output is lost.

Root cause: Both UnboundedBatchedSolaceWriter and UnboundedStreamingSolaceWriter call publishResults() in @FinishBundle without waiting for in-flight publish ACKs. The batched writer also relies on a @OnTimer("bundle_flusher") to "finalize" outputting publish results, but processing-time timers don't fire in batch pipelines before the pipeline ends.

Fix: Track the number of in-flight publish operations using an AtomicInteger counter. The counter is incremented when a publish is sent and decremented when the PublishResultHandler receives the ACK callback. In @FinishBundle, the writer waits (with a 30-second timeout) for the counter to reach 0 before emitting results.

Changes

1. PublishResultHandler.java: Accept an AtomicInteger pendingPublishCount in the constructor. Decrement it in processKey() when a publish result callback arrives.

2. SessionService.java: Add abstract method getPendingPublishCount() returning AtomicInteger.

3. JcsmpSessionService.java: Add AtomicInteger pendingPublishCount field, implement getPendingPublishCount(), pass it to PublishResultHandler.

4. UnboundedSolaceWriter.java: Add incrementPendingPublishes(int count) and waitForPendingPublishes() helper methods. The wait polls the counter with 50ms intervals up to a 30-second timeout, logging a warning if the timeout is exceeded.

5. UnboundedBatchedSolaceWriter.java: In finishBundle(), increment the pending count by the number of entries published in each batch, then call waitForPendingPublishes() before publishResults(). Also add the wait in flushBundle() (the timer handler) for consistency.

6. UnboundedStreamingSolaceWriter.java: In processElement(), increment the pending count after each successful publishSingleMessage(). In finishBundle(), call waitForPendingPublishes() before publishResults().

Testing

The existing unit tests cover the normal streaming and batched writer paths. The fix is exercised in batch pipeline mode where the @FinishBundle wait ensures ACKs are processed before results are emitted. All existing tests should continue to pass since the wait is a no-op when there are no pending publishes.

Wallet

Solana: fj4WqyCCw3C5ShR1RfB7MoBPTpkRrBFYP1uT35g3MvT

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