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https://issues.apache.org/jira/browse/KAFKA-14366?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17630581#comment-17630581
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Philip Nee commented on KAFKA-14366:
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Hey [~Chetu] - thanks for reporting this, could you kindly provide the steps to 
reproduce this issue?

> Kafka consumer rebalance issue, offsets points back to very old committed 
> offset
> --------------------------------------------------------------------------------
>
>                 Key: KAFKA-14366
>                 URL: https://issues.apache.org/jira/browse/KAFKA-14366
>             Project: Kafka
>          Issue Type: Bug
>          Components: consumer, offset manager
>    Affects Versions: 2.8.1
>         Environment: Production
>            Reporter: Chetan
>            Priority: Major
>         Attachments: rebalance issue.docx
>
>
> Hi All,
> We are facing an issue while the client consumer restart (again not all 
> restarts are ending up with this issue) and during the re-balancing scenario, 
> sometimes one of the partition offsets goes back a long way from the 
> committed offset.
> Scenario :
> Assume we have 4 instances of consumer and restarts of consumer one after the 
> other.
>  # At the time of starting restarts assume the offset on partition 10 of a 
> topic being consumed is pointing to 50000. (last offset of the topic and 0 
> lag)
>  # When restarts start (rebalancing) suddenly the offsets start pointing to 
> 20000.
>  # While all the restarts are going on the consumer who is attached starts 
> reading from 20000 and goes on.
>  # Once all rebalance is completed, and all messages from 20000 to 50000 
> offset has been read (where it had stopped initially)
> We end up having around 30K duplicates.
> (The numbers here are just an example, in production, we are facing huge 
> duplicates and every two rebalance during restarts of consumer out of 10 
> restart exercise activity ends up in such duplicates and not all partitions 
> and only one or two partitions behave this way and randomly)
> This seems to be a bug. I am attaching all screenshots for reference as well.
> Can someone kindly help out here?



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