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Date: Mon, 27 Nov 2017 17:22:00 +0000 (UTC)
From: "Jun Rao (JIRA)" <jira@apache.org>
To: jira@kafka.apache.org
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Subject: [jira] [Commented] (KAFKA-1120) Controller could miss a broker
 state change
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archived-at: Mon, 27 Nov 2017 17:22:05 -0000


    [ https://issues.apache.org/jira/browse/KAFKA-1120?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16267089#comment-16267089 ] 

Jun Rao commented on KAFKA-1120:
--------------------------------

[~mimaison], yes, the issue is still not fixed in trunk. To fix this, the controller will need to track the broker's ZK session id as you said.

> Controller could miss a broker state change 
> --------------------------------------------
>
>                 Key: KAFKA-1120
>                 URL: https://issues.apache.org/jira/browse/KAFKA-1120
>             Project: Kafka
>          Issue Type: Sub-task
>          Components: core
>    Affects Versions: 0.8.1
>            Reporter: Jun Rao
>              Labels: reliability
>             Fix For: 1.1.0
>
>
> 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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