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https://issues.apache.org/jira/browse/YARN-4041?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14966552#comment-14966552
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Sunil G commented on YARN-4041:
-------------------------------

Thank you [~jlowe] for the comments.
Yes, I was also planning to move this logic inside the waitForTokensToBeRenewed 
method, but the test failure occurred only for one test case, hence placed 
outside. I think its better we place that logic inside waitForTokensToBeRenewed 
itself as suggested. I also was not much liking the solution of sleep, however 
a better checkpoint was not raised explicitly from DelegationTokenRenewer. I 
also thought of checking the event queue size there. Now I feel we can verify 
that whether any Token renewal event is raised or not. It can be a good 
checkpoint. I will attach a patch for this with other comment fix.

> Slow delegation token renewal can severely prolong RM recovery
> --------------------------------------------------------------
>
>                 Key: YARN-4041
>                 URL: https://issues.apache.org/jira/browse/YARN-4041
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: resourcemanager
>    Affects Versions: 2.6.0
>            Reporter: Jason Lowe
>            Assignee: Sunil G
>         Attachments: 0001-YARN-4041.patch, 0002-YARN-4041.patch, 
> 0003-YARN-4041.patch
>
>
> When the RM does a work-preserving restart it synchronously tries to renew 
> delegation tokens for every active application.  If a token server happens to 
> be down or is running slow and a lot of the active apps were using tokens 
> from that server then it can have a huge impact on the time it takes the RM 
> to process the restart.



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