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https://issues.apache.org/jira/browse/KAFKA-14016?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Philip Nee resolved KAFKA-14016.
--------------------------------
    Fix Version/s: 3.5.0
                   3.4.1
         Assignee: Philip Nee
       Resolution: Fixed

> Revoke more partitions than expected in Cooperative rebalance
> -------------------------------------------------------------
>
>                 Key: KAFKA-14016
>                 URL: https://issues.apache.org/jira/browse/KAFKA-14016
>             Project: Kafka
>          Issue Type: Bug
>          Components: clients
>    Affects Versions: 3.3.0
>            Reporter: Shawn Wang
>            Assignee: Philip Nee
>            Priority: Major
>              Labels: new-rebalance-should-fix
>             Fix For: 3.5.0, 3.4.1
>
>         Attachments: CooperativeStickyAssignorBugReproduction.java
>
>
> In https://issues.apache.org/jira/browse/KAFKA-13419 we found that some 
> consumer didn't reset generation and state after sync group fail with 
> REABALANCE_IN_PROGRESS error.
> So we fixed it by reset generationId (no memberId) when  sync group fail with 
> REABALANCE_IN_PROGRESS error.
> But this change missed the reset part, so another change made in 
> https://issues.apache.org/jira/browse/KAFKA-13891 make this works.
> After apply this change, we found that: sometimes consumer will revoker 
> almost 2/3 of the partitions with cooperative enabled. Because if a consumer 
> did a very quick re-join, other consumers will get REABALANCE_IN_PROGRESS in 
> syncGroup and revoked their partition before re-jion. example:
>  # consumer A1-A10 (ten consumers) joined and synced group successfully with 
> generation 1 
>  # New consumer B1 joined and start a rebalance
>  # all consumer joined successfully and then A1 need to revoke partition to 
> transfer to B1
>  # A1 do a very quick syncGroup and re-join, because it revoked partition
>  # A2-A10 didn't send syncGroup before A1 re-join, so after the send 
> syncGruop, will get REBALANCE_IN_PROGRESS
>  # A2-A10 will revoke there partitions and re-join
> So in this rebalance almost every partition revoked, which highly decrease 
> the benefit of Cooperative rebalance 
> I think instead of "{*}resetStateAndRejoin{*} when 
> *RebalanceInProgressException* errors happend in {*}sync group{*}" we need 
> another way to fix it.
> Here is my proposal:
>  # revert the change in https://issues.apache.org/jira/browse/KAFKA-13891
>  # In Server Coordinator handleSyncGroup when generationId checked and group 
> state is PreparingRebalance. We can send the assignment along with the error 
> code REBALANCE_IN_PROGRESS. ( i think it's safe since we verified the 
> generation first )
>  # When get the REBALANCE_IN_PROGRESS error in client, try to apply the 
> assignment first and then set the rejoinNeeded = true to make it re-join 
> immediately 



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