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Posted to dev@kafka.apache.org by "Lucas Brutschy (Jira)" <ji...@apache.org> on 2026/03/09 10:09:00 UTC
[jira] [Resolved] (KAFKA-20254) Streams group replay fails after log compaction removes classic group tombstone
[ https://issues.apache.org/jira/browse/KAFKA-20254?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Lucas Brutschy resolved KAFKA-20254.
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Resolution: Fixed
> Streams group replay fails after log compaction removes classic group tombstone
> -------------------------------------------------------------------------------
>
> Key: KAFKA-20254
> URL: https://issues.apache.org/jira/browse/KAFKA-20254
> Project: Kafka
> Issue Type: Task
> Components: group-coordinator, streams
> Affects Versions: 4.2.0
> Reporter: Lucas Brutschy
> Assignee: Lucas Brutschy
> Priority: Blocker
> Fix For: 4.3.0, 4.2.1
>
>
> After offline migration from classic group to streams group, the group coordinator fails with "Group X is not a streams group" after a coordinator restart or partition reassignment.
> The offline migration (classic → streams) writes a GroupMetadataKey tombstone to delete the classic group. However, the OffsetCommitKey records for that group remain in __consumer_offsets. After log compaction removes the tombstone (past delete.retention.ms), the following happens during coordinator replay:
> 1. OffsetMetadataManager.replay encounters offset commit records without an existing group
> 2. It calls getOrMaybeCreateClassicGroup(groupId, true), which creates a simple classic group (empty, no protocol type)
> 3. When streams group records are replayed next, getOrMaybeCreatePersistedStreamsGroup finds a classic group already exists and throws "Group X is not a streams group"
>
> Trigger conditions:
> - Classic group converted to streams group via offline migration
> - Enough time passes for log compaction to clean up the GroupMetadataKey tombstone
> - Coordinator restarts or partition is reassigned, triggering a full replay
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>
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