Sylwester Lachiewicz created FLINK-40362:
--------------------------------------------
Summary: DynamicKafkaSource idle reader never finishes when
no-more-splits precedes the metadata update
Key: FLINK-40362
URL: https://issues.apache.org/jira/browse/FLINK-40362
Project: Flink
Issue Type: Bug
Components: Connectors / Kafka
Reporter: Sylwester Lachiewicz
An idle reader (a subtask with no assigned splits) that receives the
no-more-splits signal before the {{MetadataUpdateEvent}} never forwards that
signal to the sub-readers created by the update.
{{DynamicKafkaSourceReader.handleSourceEvents}} guards the re-notification with
{{!pendingSplits.isEmpty()}}, which is false in exactly this case, so
{{notifyNoMoreSplits()}} is never re-delivered. The reader then returns
{{NOTHING_AVAILABLE}} indefinitely and a bounded job never finishes.
Reproduced deterministically at unit level:
{{DynamicKafkaSourceReaderTest#testIdleReaderFinishesWhenNoMoreSplitsArrivesBeforeMetadata}}
calls {{notifyNoMoreSplits()}} before {{handleSourceEvents(metadata)}} and
then polls for {{END_OF_INPUT}}. On main it fails with "expected: END_OF_INPUT
but was: NOTHING_AVAILABLE"; with the fix it passes.
Fix: re-deliver the no-more-splits signal after processing a metadata update
regardless of whether pending splits exist. {{notifyNoMoreSplits()}} is
idempotent and only fires when the signal has already arrived, so this adds no
new cross-component traffic.
This was originally suspected of causing {{DynamicKafkaSourceITTest}}
{{testIdleReader}} hangs in CI, but that has not been reproduced locally (11/11
passes on unfixed main), so the ITCase link is unconfirmed.
Related: FLINK-40094 and FLINK-39979 touch the same reader idleness area.
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
