Jason Lowe created MAPREDUCE-4852:
-------------------------------------
Summary: Reducer should not signal fetch failures for disk errors
on the reducer's side
Key: MAPREDUCE-4852
URL: https://issues.apache.org/jira/browse/MAPREDUCE-4852
Project: Hadoop Map/Reduce
Issue Type: Bug
Components: mrv2
Reporter: Jason Lowe
Ran across a case where a reducer ran on a node where the disks were full,
leading to an exception like this during the shuffle fetch:
{noformat}
2012-12-05 09:07:28,749 INFO [fetcher#25]
org.apache.hadoop.mapreduce.task.reduce.MergeManager:
attempt_1352354913026_138167_m_000654_0: Shuffling to disk since 235056188 is
greater than maxSingleShuffleLimit (155104064)
2012-12-05 09:07:28,755 INFO [fetcher#25]
org.apache.hadoop.mapreduce.task.reduce.Fetcher: fetcher#25 failed to read map
headerattempt_1352354913026_138167_m_000654_0 decomp: 235056188, 101587629
org.apache.hadoop.util.DiskChecker$DiskErrorException: Could not find any valid
local directory for output/attempt_1352354913026_138167_r_000189_0/map_654.out
at
org.apache.hadoop.fs.LocalDirAllocator$AllocatorPerContext.getLocalPathForWrite(LocalDirAllocator.java:398)
at
org.apache.hadoop.fs.LocalDirAllocator.getLocalPathForWrite(LocalDirAllocator.java:150)
at
org.apache.hadoop.fs.LocalDirAllocator.getLocalPathForWrite(LocalDirAllocator.java:131)
at
org.apache.hadoop.mapred.YarnOutputFiles.getInputFileForWrite(YarnOutputFiles.java:213)
at
org.apache.hadoop.mapreduce.task.reduce.MapOutput.<init>(MapOutput.java:81)
at
org.apache.hadoop.mapreduce.task.reduce.MergeManager.reserve(MergeManager.java:245)
at
org.apache.hadoop.mapreduce.task.reduce.Fetcher.copyMapOutput(Fetcher.java:348)
at
org.apache.hadoop.mapreduce.task.reduce.Fetcher.copyFromHost(Fetcher.java:283)
at org.apache.hadoop.mapreduce.task.reduce.Fetcher.run(Fetcher.java:155)
2012-12-05 09:07:28,755 WARN [fetcher#25]
org.apache.hadoop.mapreduce.task.reduce.Fetcher: copyMapOutput failed for tasks
[attempt_1352354913026_138167_m_000654_0]
2012-12-05 09:07:28,756 INFO [fetcher#25]
org.apache.hadoop.mapreduce.task.reduce.ShuffleScheduler: Reporting fetch
failure for attempt_1352354913026_138167_m_000654_0 to jobtracker.
{noformat}
Even though the error was local to the reducer, it reported the error as a
fetch failure to the AM than failing the reducer itself. It then proceeded to
run into the same error for many other maps, causing them to relaunch from
reported fetch failures. In this case it would have been better to fail the
reducer and try another node rather than blame the mapper for what is an error
on the reducer's side.
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