[jira] [Assigned] (KAFKA-20449) OffsetFetcherUtils.updateSubscriptionState logs at WARN for benign race condition during rebalance

["Lianet Magrans (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-20449?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Lianet Magrans reassigned KAFKA-20449:
--------------------------------------

    Assignee: Tamas Kornai

> OffsetFetcherUtils.updateSubscriptionState logs at WARN for benign race condition during rebalance
> --------------------------------------------------------------------------------------------------
>
>                 Key: KAFKA-20449
>                 URL: https://issues.apache.org/jira/browse/KAFKA-20449
>             Project: Kafka
>          Issue Type: Bug
>          Components: clients, consumer
>    Affects Versions: 4.3.0, 4.1.2, 4.2.1
>            Reporter: Tamas Kornai
>            Assignee: Tamas Kornai
>            Priority: Major
>
> KAFKA-20131 introduced a log.warn() in OffsetFetcherUtils.updateSubscriptionState() for the case where a LIST_OFFSETS response arrives after the partition has already been revoked:
> {code:java}
> log.warn("Not updating high watermark for partition {} as it is no longer assigned", partition);
> {code}
> This is a benign race condition that naturally occurs during consumer group rebalances — a LIST_OFFSETS request is issued, the partition gets revoked before the response returns, and the response is simply
> discarded. No data loss or correctness issue arises.
> However, the WARN level is problematic in practice. Many organizations use warning log rates as a signal for canary release health. Since rebalances are frequent during rolling deployments, canary instances
> generate a high volume of these warnings, which triggers automated rollback of otherwise healthy releases.
> The log should be downgraded to DEBUG (or at most INFO), since it describes expected, harmless behavior that requires no operator action.
> Affected code:
> clients/src/main/java/org/apache/kafka/clients/consumer/internals/OffsetFetcherUtils.java, lines 281-285 (introduced in commit abcbef6a4c, PR #21457).
> Both log statements are affected:
> - "Not updating high watermark for partition {} as it is no longer assigned" (READ_UNCOMMITTED)
> - "Not updating last stable offset for partition {} as it is no longer assigned" (READ_COMMITTED)



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