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https://issues.apache.org/jira/browse/KAFKA-2841?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15005170#comment-15005170
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Guozhang Wang commented on KAFKA-2841:
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[~hachikuji] Is this solvable in KAFKA-2721?
> Group metadata cache loading is not safe when reloading a partition
> -------------------------------------------------------------------
>
> Key: KAFKA-2841
> URL: https://issues.apache.org/jira/browse/KAFKA-2841
> Project: Kafka
> Issue Type: Bug
> Affects Versions: 0.9.0.0
> Reporter: Jason Gustafson
> Assignee: Jason Gustafson
> Priority: Blocker
>
> If the coordinator receives a leaderAndIsr request which includes a higher
> leader epoch for one of the partitions that it owns, then it will reload the
> offset/metadata for that partition again. This can happen because the leader
> epoch is incremented for ISR changes which do not result in a new leader for
> the partition. Currently, the coordinator replaces cached metadata values
> blindly on reloading, which can result in weird behavior such as unexpected
> session timeouts or request timeouts while rebalancing.
> To fix this, we need to check that the group being loaded has a higher
> generation than the cached value before replacing it. Also, if we have to
> replace a cached value (which shouldn't happen except when loading), we need
> to be very careful to ensure that any active delayed operations won't affect
> the group.
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