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https://issues.apache.org/jira/browse/MAPREDUCE-5384?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13729714#comment-13729714
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Karthik Kambatla commented on MAPREDUCE-5384:
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[~sseth], good point. I thought about it, and think it should be okay for the
following reasons. Please advise if you think otherwise:
# The patch moves all the renewal/cancellation to DelegationTokenToRenew. So,
any synchronization is only on operations on one token.
# To address the issue in MAPREDUCE-4860, we should serialize the renew() and
cancel() calls for a DTTR.
# The token cancellation (RPC) is not synchronized, only the renewal is.
> Races in DelegationTokenRenewal
> -------------------------------
>
> Key: MAPREDUCE-5384
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-5384
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Affects Versions: 1.2.0, 1.1.2, 1.2.1
> Reporter: Karthik Kambatla
> Assignee: Karthik Kambatla
> Attachments: mr-5384-0.patch, mr-5384-1.patch
>
>
> There are a couple of races in DelegationTokenRenewal.
> One of them was addressed by MAPREDUCE-4860, which introduced a deadlock
> while fixing this race. Opening a new JIRA per discussion in MAPREDUCE-5364,
> since MAPREDUCE-4860 is already shipped in a release.
> Races to fix:
> # TimerTask#cancel() disallows future invocations of run(), but doesn't abort
> an already scheduled/started run().
> # 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.
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