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https://issues.apache.org/jira/browse/KAFKA-20115?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18056278#comment-18056278
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Sean Quah commented on KAFKA-20115:
-----------------------------------
I haven't checked the client code but I think they have to retry after the
rebalance timeout and not the request timeout, since JOIN_GROUP requests can be
blocked for longer than the request timeout. Once the timeout has elapsed, the
client will recover. It will either re-send the request to the old broker and
see NOT_COORDINATOR or issue a FIND_COORDINATOR directly and try the new
broker, not sure which.
The main problem is the long timeout before clients recover.
> Group coordinator fails to unload metadata when no longer leader or follower
> ----------------------------------------------------------------------------
>
> Key: KAFKA-20115
> URL: https://issues.apache.org/jira/browse/KAFKA-20115
> Project: Kafka
> Issue Type: Bug
> Components: group-coordinator
> Affects Versions: 4.0.1, 4.1.0, 4.2.0, 4.1.1
> Reporter: Sean Quah
> Assignee: Kuan Po Tseng
> Priority: Blocker
>
> KAFKA-19427 introduced logic in the coordinator runtime's
> {{freeCurrentBatch}} to only recycle batch buffers when their size is less
> than or equal to the partition's max message size.
>
> KAFKA-19519 replaced the max message size with the
> group.coordinator.cached.buffer.max.bytes and
> share.coordinator.cached.buffer.max.bytes configs.
> {{PartitionWriter.config()}} throws a {{NOT_LEADER_OR_FOLLOWER}} exception
> when the broker is no longer a leader or follower of the partition.
> When unloading partitions from the group coordinator, we try to free the
> current batch. If the broker is no longer a leader or follower of the
> {{__consumer_offsets}} partition, a {{NOT_LEADER_OR_FOLLOWER}} exception is
> thrown and we do not complete the unload process. This leaves classic group
> rebalance requests like JOIN_GROUP and SYNC_GROUP hanging.
> The bug affects versions after KAFKA-19427 and before KAFKA-19519.
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