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https://issues.apache.org/jira/browse/HDFS-12703?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16882323#comment-16882323
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Íñigo Goiri commented on HDFS-12703:
------------------------------------

Thanks [~hexiaoqiao] and [~xuel1] for working on this and [~sodonnell] for the 
review.
Committed to trunk and branch-3.2.

> Exceptions are fatal to decommissioning monitor
> -----------------------------------------------
>
>                 Key: HDFS-12703
>                 URL: https://issues.apache.org/jira/browse/HDFS-12703
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>    Affects Versions: 2.7.0
>            Reporter: Daryn Sharp
>            Assignee: He Xiaoqiao
>            Priority: Critical
>             Fix For: 3.3.0, 3.2.1
>
>         Attachments: HDFS-12703.001.patch, HDFS-12703.002.patch, 
> HDFS-12703.003.patch, HDFS-12703.004.patch, HDFS-12703.005.patch, 
> HDFS-12703.006.patch, HDFS-12703.007.patch, HDFS-12703.008.patch, 
> HDFS-12703.009.patch, HDFS-12703.010.patch, HDFS-12703.011.patch, 
> HDFS-12703.012.patch, HDFS-12703.013.patch
>
>
> The {{DecommissionManager.Monitor}} runs as an executor scheduled task.  If 
> an exception occurs, all decommissioning ceases until the NN is restarted.  
> Per javadoc for {{executor#scheduleAtFixedRate}}: *If any execution of the 
> task encounters an exception, subsequent executions are suppressed*.  The 
> monitor thread is alive but blocked waiting for an executor task that will 
> never come.  The code currently disposes of the future so the actual 
> exception that aborted the task is gone.
> Failover is insufficient since the task is also likely dead on the standby.  
> Replication queue init after the transition to active will fix the under 
> replication of blocks on currently decommissioning nodes but future nodes 
> never decommission.  The standby must be bounced prior to failover – and 
> hopefully the error condition does not reoccur.



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