NIFI-15835 - Flaky test PollingKinesisClientTest.testExpiredIteratorRecoveryDoesNotDeliverSameShardOutOfOrder

[pvillard31]

Summary

NIFI-15835 - Flaky test PollingKinesisClientTest.testExpiredIteratorRecoveryDoesNotDeliverSameShardOutOfOrder

The fetch loop runs with 1-nanosecond backoffs, so on some thread schedules it could complete the entire cycle (fetch seq 200, fetch seq 300, hit ExpiredIteratorException, drain the shard queue, replay from checkpoint) before the test thread's first pollAnyResult call. The drain removed both batches (including the one the test expected to poll first), and the replay batch was consumed by the first poll, leaving nothing for the second poll -- which then returned null after 5 seconds.

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[exceptionfactory]

Thanks @pvillard31, this alternative approach looks like a good improvement for test stability. +1 merging