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https://issues.apache.org/jira/browse/KAFKA-13296?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sagar Rao resolved KAFKA-13296.
-------------------------------
    Resolution: Fixed

> 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
>            Assignee: Sagar Rao
>            Priority: Major
>
> `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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