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From "Naganarasimha G R (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-2919) Potential race between renew and cancel in DelegationTokenRenwer
Date Thu, 13 Jul 2017 15:14:00 GMT

    [ https://issues.apache.org/jira/browse/YARN-2919?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16085850#comment-16085850
] 

Naganarasimha G R commented on YARN-2919:
-----------------------------------------

Thanks [~jianhe] for the feeback.

bq. Unless we completely synchronize the cancel and renew at client side which will bring
more overhead, it is possible for a renew happen immediately after a cancel.
Agree that patch works currently on the best effort and does not completely ensure race is
avoided. But instead if we synchronize the {{Token.renew(Configuration)}} & {{Token.cancel(configuration)}},
and also have a simple boolean in {{Token}} to signify the cancelling flow should ensure that
the race is fully avoided.
And in terms of cost *renew* is called not very frequently and *cancel* only once, and if
use read write locks if really required then should be pretty fast. Thoughts ?

bq.In the context of DelegationTokenRenewal, RenewalTimerTask#cancel() only cancels that TimerTask
instance. However, it has no effect on any other TimerTasks created for that token. 
 [~jianhe] could there be chances for this ? IIUC there is only one Dttr per Token  and hence
only one timer task right?

Also would like to know the feedback from [~kasha] as the issue was raised by him.


> Potential race between renew and cancel in DelegationTokenRenwer 
> -----------------------------------------------------------------
>
>                 Key: YARN-2919
>                 URL: https://issues.apache.org/jira/browse/YARN-2919
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: security
>    Affects Versions: 2.6.0
>            Reporter: Karthik Kambatla
>            Assignee: Naganarasimha G R
>            Priority: Critical
>         Attachments: YARN-2919.002.patch, YARN-2919.003.patch, YARN-2919.004.patch, YARN-2919.005.patch,
YARN-2919.20141209-1.patch
>
>
> YARN-2874 fixes a deadlock in DelegationTokenRenewer, but there is still a race because
of which a renewal in flight isn't interrupted by a cancel. 



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