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From "Yongjun Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6289) HA failover can fail if there are pending DN messages for DNs which no longer exist
Date Sat, 26 Apr 2014 00:20:18 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6289?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13981791#comment-13981791
] 

Yongjun Zhang commented on HDFS-6289:
-------------------------------------

Thanks for answering my questions ATM, that helps!


> HA failover can fail if there are pending DN messages for DNs which no longer exist
> -----------------------------------------------------------------------------------
>
>                 Key: HDFS-6289
>                 URL: https://issues.apache.org/jira/browse/HDFS-6289
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: ha
>    Affects Versions: 2.4.0
>            Reporter: Aaron T. Myers
>            Assignee: Aaron T. Myers
>            Priority: Critical
>         Attachments: HDFS-6289.patch
>
>
> In an HA setup, the standby NN may receive messages from DNs for blocks which the standby
NN is not yet aware of. It queues up these messages and replays them when it next reads from
the edit log or fails over. On a failover, all of these pending DN messages must be processed
successfully in order for the failover to succeed. If one of these pending DN messages refers
to a DN storageId that no longer exists (because the DN with that transfer address has been
reformatted and has re-registered with the same transfer address) then on transition to active
the NN will not be able to process this DN message and will suicide with an error like the
following:
> {noformat}
> 2014-04-25 14:23:17,922 FATAL namenode.NameNode (NameNode.java:doImmediateShutdown(1525))
- Error encountered requiring NN shutdown. Shutting down immediately.
> java.io.IOException: Cannot mark blk_1073741825_900(stored=blk_1073741825_1001) as corrupt
because datanode 127.0.0.1:33324 does not exist
> {noformat}



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