[jira] [Resolved] (KAFKA-17796) Persist higher leaderEpoch in read state calls to the share coordinator.

["Andrew Schofield (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-17796?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Andrew Schofield resolved KAFKA-17796.
--------------------------------------
    Resolution: Fixed

> Persist higher leaderEpoch in read state calls to the share coordinator.
> ------------------------------------------------------------------------
>
>                 Key: KAFKA-17796
>                 URL: https://issues.apache.org/jira/browse/KAFKA-17796
>             Project: Kafka
>          Issue Type: Sub-task
>            Reporter: Sushant Mahajan
>            Assignee: Sushant Mahajan
>            Priority: Major
>             Fix For: 4.0.0
>
>
> It is possible that a ReadShareStateRequest includes a higher leader epoch for a specific share partition than previously seen by the share coordinator.
> However, currently we are only persisting the leaderEpoch in the write state calls. We need to implement the logic to write a record to the __share_group_state internal topic when a higher leaderEpoch is seen in read state calls.
> One way to accomplish this is to make a an additional write state call with every read call if the read state request contains a higher leaderEpoch for a share partition. We are already maintaining highest leaderEpoch in share coordinator soft state of the topic.
> This will increase load on the share coordinator due to the occasional extra write but the read calls are relatively rare (compared to write). Read calls are made when a new share partition is initialized for the first time.
>  
> Classes affected:
> ShareCoordinatorService.java
> ShareCoordinatorShard.java



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