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https://issues.apache.org/jira/browse/MAPREDUCE-2541?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Binglin Chang updated MAPREDUCE-2541:
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Status: Patch Available (was: Open)
patch to 0.21 branch. Make IndexCache.removeMap() do nothing
> Race Condition in IndexCache(readIndexFileToCache,removeMap) causes value of
> totalMemoryUsed corrupt, which may cause TaskTracker continue throw Exception
> ----------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-2541
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-2541
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: tasktracker
> Affects Versions: 0.21.0, 0.20.1, 0.22.0, 0.23.0
> Environment: all
> Reporter: Binglin Chang
> Priority: Critical
>
> The race condition goes like this:
> Thread1: readIndexFileToCache() totalMemoryUsed.addAndGet(newInd.getSize())
> Thread2: removeMap() totalMemoryUsed.addAndGet(-info.getSize());
> When SpillRecord is being read from fileSystem, client kills the job,
> info.getSize() equals 0, so in fact totalMemoryUsed is not reduced, but after
> thread1 finished reading SpillRecord, it adds the real index size to
> totalMemoryUsed, which makes the value of totalMemoryUsed wrong(larger).
> When this value(totalMemoryUsed) exceeds totalMemoryAllowed (this usually
> happens when a vary large job with vary large reduce number is killed by the
> user, probably because the user sets a wrong reduce number by mistake), and
> actually indexCache has not cache anything, freeIndexInformation() will throw
> exception constantly.
> A quick fix for this issue is to make removeMap() do nothing, let
> freeIndexInformation() do this job only.
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