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https://issues.apache.org/jira/browse/YARN-3639?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14544235#comment-14544235
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Allen Wittenauer commented on YARN-3639:
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OK, just making sure there wasn't some weird thing going on where the problem 
really did exist because they happened to be on the same node.  That'd be very 
very bad. :D

> It takes too long time for RM to recover all apps if the original active RM 
> and NN go down at the same time.
> ------------------------------------------------------------------------------------------------------------
>
>                 Key: YARN-3639
>                 URL: https://issues.apache.org/jira/browse/YARN-3639
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: resourcemanager
>            Reporter: Xianyin Xin
>         Attachments: YARN-3639-recovery_log_1_app.txt
>
>
> If the active RM and NN go down at the same time, the new RM will take long 
> time to recover all apps. After analysis, we found the root cause is renewing 
> HDFS tokens in the recovering process. The HDFS client created by the renewer 
> would firstly try to connect to the original NN, the result of which is 
> time-out after 10~20s, and then the client tries to connect to the new NN. 
> The entire recovery cost 15*#apps seconds according our test.



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