Sylwester Lachiewicz created FLINK-40136:
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Summary: DynamicKafkaSourceEnumeratorTest flaky due to
ConcurrentModificationException in metadata event polling
Key: FLINK-40136
URL: https://issues.apache.org/jira/browse/FLINK-40136
Project: Flink
Issue Type: Bug
Reporter: Sylwester Lachiewicz
▎ hasLatestMetadataUpdateEvent() polls
getLatestMetadataUpdateEventWithoutContextSync(), which reads
MockSplitEnumeratorContext's internal sentSourceEvent list via reflection
directly from the JUnit test thread, bypassing the context's single-threaded
main executor. The enumerator's metadata discovery thread appends to that same
list via sendEventToSourceReader() (correctly serialized through the main
executor), so a test thread iterating the list via Stream.reduce() while that
thread appends to it occasionally throws ConcurrentModificationException
instead of the intended AssertionError "not ready yet" signal, causing
intermittent test failures.
▎ Fix: catch ConcurrentModificationException alongside AssertionError in the
CommonTestUtils.waitUtil(...) polling loop so it retries instead of failing the
test.
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