[jira] [Work started] (KAFKA-4229) Controller can't start after several zk expired event

["Pengwei (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-4229?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Work on KAFKA-4229 started by Pengwei.
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> Controller can't start after several zk expired event
> -----------------------------------------------------
>
>                 Key: KAFKA-4229
>                 URL: https://issues.apache.org/jira/browse/KAFKA-4229
>             Project: Kafka
>          Issue Type: Bug
>          Components: controller
>    Affects Versions: 0.9.0.0, 0.9.0.1, 0.10.0.0, 0.10.0.1
>            Reporter: Pengwei
>            Assignee: Pengwei
>
> We found the controller not started after several zk expired event in our test environment.  By analysing the log, I found the controller will handle the ephemeral node data delete event first and then the zk expired event , then the controller will gone.
> I can reproducer it on my develop env:
> 1. set up a one broker and one zk env, specify a very large zk timeout (20s)
> 2. stop the broker and remove the zk's /broker/ids/0  directory
> 3. restart the broker and make  a breakpoint in the zk client's event thread to queue the delete event.
> 4. after the /controller node gone the breakpoint will hit.
> 5. expired the current session(suspend the send thread) and create a new session s2
> 6. resume the event thread, then the controller will handle LeaderChangeListener.handleDataDeleted  and become leader
> 7. then controller will handle SessionExpirationListener.handleNewSession, it resign the controller and elect,  but when elect it found the /controller node is exist and not become the leader.  But the /controller node is created by current session s2 will not remove. So the controller is gone



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