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https://issues.apache.org/jira/browse/MAPREDUCE-1347?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Harsh J updated MAPREDUCE-1347:
-------------------------------
Attachment: MAPREDUCE-1347.r9.diff
Updated (rebased) patch that just fixes the issue and uses the right test
location.
Removed ivy markers as those are irrelevant today (for guava is already
available).
For moving the tests, since there seem to be lots of tests lying split like
that, lets discuss/investigate it over at MAPREDUCE-4253 instead.
> Missing synchronization in MultipleOutputFormat
> -----------------------------------------------
>
> Key: MAPREDUCE-1347
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-1347
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Affects Versions: 1.0.0
> Reporter: Todd Lipcon
> Assignee: Harsh J
> Attachments: MAPREDUCE-1347.r2.diff, MAPREDUCE-1347.r3.diff,
> MAPREDUCE-1347.r4.diff, MAPREDUCE-1347.r5.diff, MAPREDUCE-1347.r6.diff,
> MAPREDUCE-1347.r7.diff, MAPREDUCE-1347.r8.diff, MAPREDUCE-1347.r9.diff,
> mapreduce.1347.r1.diff
>
>
> MultipleOutputFormat's RecordWriter implementation doesn't use
> synchronization when accessing the recordWriters member. When using
> multithreaded mappers or reducers, this can result in problems where two
> threads will both try to create the same file, causing
> AlreadyBeingCreatedException. Doing this more fine-grained than just
> synchronizing the whole method is probably a good idea, so that multithreaded
> mappers can actually achieve parallelism writing into separate output streams.
> From what I can tell, the new API's MultipleOutputs seems not to have this
> issue.
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