Guozhang Wang created KAFKA-12920:
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Summary: Consumer's cooperative sticky assignor need to clear
generation / assignment data upon `onPartitionsLost`
Key: KAFKA-12920
URL: https://issues.apache.org/jira/browse/KAFKA-12920
Project: Kafka
Issue Type: Improvement
Reporter: Guozhang Wang
Consumer's cooperative-sticky assignor does not track the owned partitions
inside the assignor --- i.e. when it reset its state in event of
``onPartitionsLost``, the ``memberAssignment`` and ``generation`` inside the
assignor would not be cleared. This would cause a member to join with empty
generation on the protocol while with non-empty user-data encoding the old
assignment still (and hence pass the validation check on broker side during
JoinGroup), and eventually cause a single partition to be assigned to multiple
consumers within a generation.
We should let the assignor to also clear its assignment/generation when
``onPartitionsLost`` is triggered in order to avoid this scenario.
Note that 1) for the regular sticky assignor the generation would still have an
older value, and this would cause the previously owned partitions to be
discarded during the assignment, and 2) for Streams' sticky assignor, it’s
encoding would indeed be cleared along with ``onPartitionsLost``. Hence only
Consumer's cooperative-sticky assignor have this issue to solve.
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