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https://issues.apache.org/jira/browse/KAFKA-1120?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15750982#comment-15750982
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Ben Stopford commented on KAFKA-1120:
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[~junrao] added this comment on a mail thread on this topic which is useful:
https://www.mail-archive.com/dev@kafka.apache.org/msg62261.html
> Controller could miss a broker state change
> --------------------------------------------
>
> Key: KAFKA-1120
> URL: https://issues.apache.org/jira/browse/KAFKA-1120
> Project: Kafka
> Issue Type: Bug
> Components: core
> Affects Versions: 0.8.1
> Reporter: Jun Rao
> Labels: reliability
>
> When the controller is in the middle of processing a task (e.g., preferred
> leader election, broker change), it holds a controller lock. During this
> time, a broker could have de-registered and re-registered itself in ZK. After
> the controller finishes processing the current task, it will start processing
> the logic in the broker change listener. However, it will see no broker
> change and therefore won't do anything to the restarted broker. This broker
> will be in a weird state since the controller doesn't inform it to become the
> leader of any partition. Yet, the cached metadata in other brokers could
> still list that broker as the leader for some partitions. Client requests
> routed to that broker will then get a TopicOrPartitionNotExistException. This
> broker will continue to be in this bad state until it's restarted again.
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