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From "Karthik Kambatla (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-5384) Races in DelegationTokenRenewal
Date Mon, 05 Aug 2013 17:52:48 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-5384?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13729714#comment-13729714
] 

Karthik Kambatla commented on MAPREDUCE-5384:
---------------------------------------------

[~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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