Race Condition in IndexCache(readIndexFileToCache,removeMap) causes value of
totalMemoryUsed corrupt, which may cause TaskTracker continue throw Exception
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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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