[ http://issues.apache.org/jira/browse/HADOOP-723?page=all ]
Owen O'Malley updated HADOOP-723:
---------------------------------
Status: Patch Available (was: Open)
Fix Version/s: 0.9.0
Affects Version/s: 0.8.0
> Race condition exists in the method MapOutputLocation.getFile
> -------------------------------------------------------------
>
> Key: HADOOP-723
> URL: http://issues.apache.org/jira/browse/HADOOP-723
> Project: Hadoop
> Issue Type: Bug
> Components: mapred
> Affects Versions: 0.8.0
> Reporter: Devaraj Das
> Assigned To: Owen O'Malley
> Fix For: 0.9.0
>
> Attachments: map-out-lost.patch
>
>
> There seems to be a race condition in the way the Reduces copy the map output
> files from the Maps. If a copier is blocked in the connect method (in the
> beginning of the method MapOutputLocation.getFile) to a Jetty on a Map, and
> the MapCopyLeaseChecker detects that the copier was idle for too long, it
> will go ahead and issue a interrupt (read 'kill') to this thread and create a
> new Copier thread. However, the copier, currently blocked trying to connect
> to Jetty on a Map, doesn't actually get killed until the connect timeout
> expires and as soon as the connect comes out (with an IOException), it will
> delete the map output file which actually could have been (successfully)
> created by the new Copier thread. This leads to the Sort phase for that
> reducer failing with a FileNotFoundException.
> One simple way to fix this is to not delete the file if the file was not
> created within this getFile method.
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