[jira] Commented: (MAPREDUCE-1347) Missing synchronization in MultipleOutputFormat

["Hadoop QA (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAPREDUCE-1347?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13000855#comment-13000855 ] 

Hadoop QA commented on MAPREDUCE-1347:
--------------------------------------

-1 overall.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12471975/mapreduce.1347.r1.diff
  against trunk revision 1075670.

    +1 @author.  The patch does not contain any @author tags.

    -1 tests included.  The patch doesn't appear to include any new or modified tests.
                        Please justify why no new tests are needed for this patch.
                        Also please list what manual steps were performed to verify this patch.

    +1 javadoc.  The javadoc tool did not generate any warning messages.

    +1 javac.  The applied patch does not increase the total number of javac compiler warnings.

    +1 findbugs.  The patch does not introduce any new Findbugs (version 1.3.9) warnings.

    +1 release audit.  The applied patch does not increase the total number of release audit warnings.

    +1 core tests.  The patch passed core unit tests.

    -1 contrib tests.  The patch failed contrib unit tests.

    +1 system test framework.  The patch passed system test framework compile.

Test results: https://hudson.apache.org/hudson/job/PreCommit-MAPREDUCE-Build/106//testReport/
Findbugs warnings: https://hudson.apache.org/hudson/job/PreCommit-MAPREDUCE-Build/106//artifact/trunk/build/test/findbugs/newPatchFindbugsWarnings.html
Console output: https://hudson.apache.org/hudson/job/PreCommit-MAPREDUCE-Build/106//console

This message is automatically generated.

> 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: 0.20.2, 0.21.0, 0.22.0
>            Reporter: Todd Lipcon
>            Assignee: Harsh J Chouraria
>         Attachments: 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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