[jira] [Resolved] (KAFKA-20694) Fix share coordinator readState leaderEpoch -1 sentinel fencing

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

     [ https://issues.apache.org/jira/browse/KAFKA-20694?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Andrew Schofield resolved KAFKA-20694.
--------------------------------------
    Resolution: Fixed

> Fix share coordinator readState leaderEpoch -1 sentinel fencing
> ---------------------------------------------------------------
>
>                 Key: KAFKA-20694
>                 URL: https://issues.apache.org/jira/browse/KAFKA-20694
>             Project: Kafka
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 4.2.1
>            Reporter: Shekhar Prasad Rajak
>            Assignee: Shekhar Prasad Rajak
>            Priority: Major
>             Fix For: 4.4.0, 4.3.2
>
>
> ShareCoordinatorShard.readStateAndMaybeUpdateLeaderEpoch treats leaderEpoch == -1 as a sentinel meaning “do not update leader epoch”, but maybeGetReadStateError fences the request before
>   that logic runs when the stored leader epoch is greater than -1. This causes valid no-update readState requests to return FENCED_LEADER_EPOCH.
>   *Expected behavior:*
>   When ReadShareGroupStateRequest has leaderEpoch == -1, share coordinator should not update the stored leader epoch and should not apply stale-leader fencing. The response should succeed
>   with Errors.NONE and produce no coordinator record.
>   *Wrong scenario:*
>   Stored leader epoch for share partition is 2.
>   A readState request arrives with leaderEpoch=-1.
>   Current code compares 2 > -1 and returns FENCED_LEADER_EPOCH.
>   Expected: success response, no generated record, stored leader epoch remains 2.
>   *Test gap:*
>   testReadStateLeaderEpochUpdateNoUpdate only checks that no records are generated. A fenced response also generates no records, so the test passes incorrectly. Add assertion that the
>   response partition error code is Errors.NONE.



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