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https://issues.apache.org/jira/browse/MAPREDUCE-1347?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13054631#comment-13054631
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jirapos...@reviews.apache.org commented on MAPREDUCE-1347:
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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/953/
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Review request for hadoop-mapreduce and Todd Lipcon.
Summary
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Used the makeComputingMap from Guava's MapMaker to provide a thread safe way of
creating a RecordWriter cache.
For some reason, the map is not really caching it and is instead trying to
apply() over and over again for the same key-value pairs.
This addresses bug MAPREDUCE-1347.
http://issues.apache.org/jira/browse/MAPREDUCE-1347
Diffs
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mapreduce/ivy.xml 85ee014
mapreduce/ivy/libraries.properties 9d40aaa
mapreduce/src/java/org/apache/hadoop/mapred/lib/MultipleOutputFormat.java
b8944f1
mapreduce/src/test/mapred/org/apache/hadoop/mapred/TestMultipleTextOutputFormat.java
14c097d
Diff: https://reviews.apache.org/r/953/diff
Testing
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Added a test case, but it fails with the current behavior of MapMaker's
makeComputingMap() (would pass if its alright)
Thanks,
Harsh
> 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
> Attachments: MAPREDUCE-1347.r2.diff, MAPREDUCE-1347.r3.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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