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https://issues.apache.org/jira/browse/YARN-2919?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16077190#comment-16077190
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Jian He commented on YARN-2919:
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bq. assume RenewalTimerTask. run is invoked by the timer task and it has passed
through the if (!dttr.isTimerCancelled()) but before
renewToken(DelegationTokenToRenew) or in between renewToken &
setTimerForTokenRenewal is invoked, removeApplicationFromRenewal gets
triggered. In which case unnecessary renew or timer task scheduling happens
I think there's always such situation regardless whether the flag is inside the
method (done by this patch) or outside the method ( the cancelled flag which
exists today). e.g. In current patch, if the renew Method has passed the {{if
(!cancelling.get()) {}} check, and before renew invokes, the cancel is
executed, then the renewToken will also be executed ? 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.
On the other hand, it is possible, but rare, for the mentioned scenario to
occur because {{dttr.cancelTimer();}} will cancel the timer and the followup
cancelToken(dttr) doesnot cancel the token immediately, but rather enqueues the
cancel the task which should have more room for the other parallel executing
renewal thread to run into completion.
Anyway, we could try to synchronize both operations completely to avoid this
rare scenario but at the cost of more overhead, or we have a good fallback
code to handle this failed scenario as it does today. (btw, do you know if this
issue occur in reality or it's a observation by code?) IMHO, the current
existing way maybe fine..
> 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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