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https://issues.apache.org/jira/browse/KAFKA-14196?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17599705#comment-17599705
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Philip Nee commented on KAFKA-14196:
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I'm tracing the code path, it seems like the poll() continues to happen during 
the rebalance process; however, no commit is being issued due to the 
coordinator poll() returns (ensureActiveGroup check) before sending out the 
commit.  I'm not sure why do we want to return early in that block.  Is there a 
reason why we don't want to commit before finishing the rebalancing process?

> Flaky OffsetValidationTest seems to indicate potential duplication issue 
> during rebalance
> -----------------------------------------------------------------------------------------
>
>                 Key: KAFKA-14196
>                 URL: https://issues.apache.org/jira/browse/KAFKA-14196
>             Project: Kafka
>          Issue Type: Bug
>          Components: clients, consumer
>    Affects Versions: 3.2.1
>            Reporter: Philip Nee
>            Assignee: Philip Nee
>            Priority: Major
>
> Several flaky tests under OffsetValidationTest are indicating potential 
> consumer duplication issue, when autocommit is enabled.  Below shows the 
> failure message:
>  
> {code:java}
> Total consumed records 3366 did not match consumed position 3331 {code}
>  
> After investigating the log, I discovered that the data consumed between the 
> start of a rebalance event and the async commit was lost for those failing 
> tests.  In the example below, the rebalance event kicks in at around 
> 1662054846995 (first record), and the async commit of the offset 3739 is 
> completed at around 1662054847015 (right before partitions_revoked).
>  
> {code:java}
> {"timestamp":1662054846995,"name":"records_consumed","count":3,"partitions":[{"topic":"test_topic","partition":0,"count":3,"minOffset":3739,"maxOffset":3741}]}
> {"timestamp":1662054846998,"name":"records_consumed","count":2,"partitions":[{"topic":"test_topic","partition":0,"count":2,"minOffset":3742,"maxOffset":3743}]}
> {"timestamp":1662054847008,"name":"records_consumed","count":2,"partitions":[{"topic":"test_topic","partition":0,"count":2,"minOffset":3744,"maxOffset":3745}]}
> {"timestamp":1662054847016,"name":"partitions_revoked","partitions":[{"topic":"test_topic","partition":0}]}
> {"timestamp":1662054847031,"name":"partitions_assigned","partitions":[{"topic":"test_topic","partition":0}]}
> {"timestamp":1662054847038,"name":"records_consumed","count":23,"partitions":[{"topic":"test_topic","partition":0,"count":23,"minOffset":3739,"maxOffset":3761}]}
>  {code}
> A few things to note here:
>  # This is highly flaky, I found 1/4 runs will fail the tests
>  # Manually calling commitSync in the onPartitionsRevoke cb seems to 
> alleviate the issue
>  # Setting includeMetadataInTimeout to false also seems to alleviate the 
> issue.
>  



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