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https://issues.apache.org/jira/browse/KAFKA-10301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17165484#comment-17165484
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Stanislav Kozlovski commented on KAFKA-10301:
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Merged in master
([fa6e5b892227db24568e2cec0a0a0969bc1ec4b5|https://github.com/apache/kafka/commit/fa6e5b892227db24568e2cec0a0a0969bc1ec4b5])
and 2.6
([fb0a79ddc7c2144cd58b9fc27e4d36ab8f063a78|https://github.com/apache/kafka/commit/fb0a79ddc7c2144cd58b9fc27e4d36ab8f063a78])
> Partition#remoteReplicasMap can be empty in certain race conditions
> -------------------------------------------------------------------
>
> Key: KAFKA-10301
> URL: https://issues.apache.org/jira/browse/KAFKA-10301
> Project: Kafka
> Issue Type: Bug
> Reporter: Stanislav Kozlovski
> Assignee: Stanislav Kozlovski
> Priority: Blocker
>
> In Partition#updateAssignmentAndIsr, we would previously update the
> `partition#remoteReplicasMap` by adding the new replicas to the map and then
> removing the old ones
> ([source]([https://github.com/apache/kafka/blob/7f9187fe399f3f6b041ca302bede2b3e780491e7/core/src/main/scala/kafka/cluster/Partition.scala#L657)]
> During a recent refactoring, we changed it to first clear the map and then
> add all the replicas to it
> ([source]([https://github.com/apache/kafka/blob/2.6/core/src/main/scala/kafka/cluster/Partition.scala#L663]))
> While this is done in a write lock (`inWriteLock(leaderIsrUpdateLock)`), not
> all callers that access the map structure use a lock. Some examples:
> - Partition#updateFollowerFetchState
> - DelayedDeleteRecords#tryComplete
> - Partition#getReplicaOrException - called in
> `checkEnoughReplicasReachOffset` without a lock, which itself is called by
> DelayedProduce. I think this can fail a `ReplicaManager#appendRecords` call.
> While we want to polish the code to ensure these sort of race conditions
> become harder (or impossible) to introduce, it sounds safest to revert to the
> previous behavior given the timelines regarding the 2.6 release. Jira
> https://issues.apache.org/jira/browse/KAFKA-10302 tracks further
> modifications to the code.
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