[jira] [Created] (KAFKA-13296) Verify old assignment within StreamsPartitionAssignor

["Matthias J. Sax (Jira)" <ji...@apache.org>]

Matthias J. Sax created KAFKA-13296:
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             Summary: Verify old assignment within StreamsPartitionAssignor
                 Key: KAFKA-13296
                 URL: https://issues.apache.org/jira/browse/KAFKA-13296
             Project: Kafka
          Issue Type: Improvement
          Components: streams
            Reporter: Matthias J. Sax


`StreamsPartitionAssignor` is responsible to assign partitions and tasks to all StreamsThreads within an application.

While it ensures to not assign a single partition/task to two threads, there is limited verification about it. In particular, we had one incident for with a zombie thread/consumer did not cleanup its own internal state correctly due to KAFKA-12983. This unclean zombie-state implied that the _old assignment_ reported to `StreamsPartitionAssignor` contained a single partition for two consumers. As a result, both threads/consumers later revoked the same partition and the zombie-thread could commit it's unclean work (even if it should have been fenced), leading to duplicate output under EOS_v2.

We should consider to add a check to `StreamsPartitionAssignor` if the _old assignment_ is valid, ie, no partition should be missing and no partition should be assigned to two consumers. For this case, we should log the invalid _old assignment_ and send an error code back to all consumer that indicates that they should shut down "unclean" (ie, without and flushing and no committing any offsets or transactions).



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