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From "Karthik Kambatla (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (MAPREDUCE-5384) Races in DelegationTokenRenewal
Date Tue, 06 Aug 2013 21:00:48 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-5384?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Karthik Kambatla updated MAPREDUCE-5384:
----------------------------------------

    Attachment: mr-5384-2.patch

[~sseth], very good point. In my testing, I noticed the renewal RPC takes about 5 ms and could
take longer.

Uploading a patch that addresses this issue
# Call token.renew() outside of a synchronized block
# To address the potential race with cancel(), cancel() now returns a boolean - true if it
successfully cancels all renewals and false if there is a renewal currently in progress. Renewing
once after the cancel() is called is benign, but the user can be intimated about this renewal
in progress.
# TestDelegationTokenRenewal uses this intimation to allow for an extra renewal.

Testing: Ran the new TestDelegationTokenRenewal in a loop 10 times and it passed.
                
> 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, mr-5384-2.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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