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https://issues.apache.org/jira/browse/KAFKA-17507?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Justine Olshan resolved KAFKA-17507.
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Fix Version/s: 4.0.0
Resolution: Fixed
The new group coordinator will be used in 4.0.0 which does not have this issue.
We decided not to fix for 3.9 as this bug is not a new regression to the
release.
> WriteTxnMarkers API must not return until markers are written and
> materialized in group coordinator's cache
> -----------------------------------------------------------------------------------------------------------
>
> Key: KAFKA-17507
> URL: https://issues.apache.org/jira/browse/KAFKA-17507
> Project: Kafka
> Issue Type: Bug
> Reporter: David Jacot
> Assignee: David Jacot
> Priority: Major
> Fix For: 4.0.0
>
>
> We have observed the below errors in some cluster:
> Uncaught exception in scheduled task 'handleTxnCompletion-902667'
> exception.message:Trying to complete a transactional offset commit for
> producerId *** and groupId *** even though the offset commit record itself
> hasn't been appended to the log.
> When a transaction is completed, the transaction coordinator sends a
> WriteTxnMarkers request to all the partitions involved in the transaction to
> write the markers to them. When the broker receives it, it writes the markers
> and if markers are written to the __consumer_offsets partitions, it informs
> the group coordinator that it can materialize the pending transactional
> offsets in its main cache. The group coordinator does this asynchronously
> since Apache Kafka 2.0, see this
> [patch|https://github.com/apache/kafka/commit/c53e274d3128bc92f0e8b6a79c407cf764f16f7b].
> The above error appends when the asynchronous operation is executed by the
> scheduler and the operation finds that there are pending transactional
> offsets that were not written yet. How come?
> There is actually an issue is the steps described above. The group
> coordinator does not wait until the asynchronous operation completes to
> return to the api layer. Hence the WriteTxnMarkers response may be send back
> to the transaction coordinator before the async operation is actually
> completed. Hence it is possible that the next transactional produce to be
> started also before the operation is completed too. This could explain why
> the group coordinator has pending transactional offsets that are not written
> yet.
> There is a similar issue when the transaction is aborted. However on this
> path, we don't have any checks to verify whether all the pending
> transactional offsets have been written or not so we don't see any errors in
> our logs. Due to the same race condition, it is possible to actually remove
> the wrong pending transactional offsets.
> PS: The new group coordinator is not impacted by this bug.
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