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https://issues.apache.org/jira/browse/KAFKA-13227?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17413479#comment-17413479
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Christo Lolov commented on KAFKA-13227:
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[~hachikuji] Apologies for the delay, I wasn't able to find the time to look
further into this before today. I read KIP-497, have been going through the
code and I am slightly confused. As far as I can tell, the above WARN message
is logged whenever a newer _AlterIsr_ request is enqueued to be sent and we
find a still unsent _AlterIsr_ request for the same _topicPartition_ in the
_unsentIsrUpdates_ map, which we overwrite and forget about. Since this happens
before we send the older _AlterIsr_ request do we have to take care of its
callback? Or am I misunderstanding the code?
> Cancel pending AlterIsr requests after receiving LeaderAndIsr
> -------------------------------------------------------------
>
> Key: KAFKA-13227
> URL: https://issues.apache.org/jira/browse/KAFKA-13227
> Project: Kafka
> Issue Type: Improvement
> Reporter: Jason Gustafson
> Assignee: Christo Lolov
> Priority: Major
>
> Currently we do not cancel pending AlterIsr requests after the state has been
> updated through a LeaderAndIsr request received from the controller. This
> leads to log messages such as this
> {code}
> [2021-08-23 18:12:47,317] WARN [Partition __transaction_state-32 broker=3]
> Failed to enqueue ISR change state LeaderAndIsr(leader=3, leaderEpoch=3,
> isUncleanLeader=false, isr=List(3, 1), zkVersion=3) for partition
> __transaction_state-32 (kafka.cluster.Partition)
> {code}
> I think the only complication here is protecting against the AlterIsr
> callback which is executed asynchronously. To address this, we can move the
> `zkVersion` field into `IsrState`. When the callback is invoked, we can the
> existing state against the response state to decide whether to apply the
> change.
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