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Hadoop QA commented on MAPREDUCE-4842: -------------------------------------- {color:green}+1 overall{color}. Here are the results of testing the latest attachment http://issues.apache.org/jira/secure/attachment/12561957/mapreduce-4842.patch against trunk revision . {color:green}+1 @author{color}. The patch does not contain any @author tags. {color:green}+1 tests included{color}. The patch appears to include 1 new or modified test files. {color:green}+1 javac{color}. The applied patch does not increase the total number of javac compiler warnings. {color:green}+1 javadoc{color}. The javadoc tool did not generate any warning messages. {color:green}+1 eclipse:eclipse{color}. The patch built with eclipse:eclipse. {color:green}+1 findbugs{color}. The patch does not introduce any new Findbugs (version 1.3.9) warnings. {color:green}+1 release audit{color}. The applied patch does not increase the total number of release audit warnings. {color:green}+1 core tests{color}. The patch passed unit tests in hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core. {color:green}+1 contrib tests{color}. The patch passed contrib unit tests. Test results: https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/3149//testReport/ Console output: https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/3149//console This message is automatically generated. > Shuffle race can hang reducer > ----------------------------- > > Key: MAPREDUCE-4842 > URL: https://issues.apache.org/jira/browse/MAPREDUCE-4842 > Project: Hadoop Map/Reduce > Issue Type: Bug > Components: mrv2 > Affects Versions: 2.0.2-alpha, 0.23.5 > Reporter: Jason Lowe > Assignee: Mariappan Asokan > Priority: Blocker > Attachments: MAPREDUCE-4842-2.patch, mapreduce-4842.patch, > mapreduce-4842.patch, mapreduce-4842.patch, mapreduce-4842.patch, > MAPREDUCE-4842.patch, MAPREDUCE-4842.patch, MAPREDUCE-4842.patch, > MAPREDUCE-4842.patch > > > Saw an instance where the shuffle caused multiple reducers in a job to hang. > It looked similar to the problem described in MAPREDUCE-3721, where the > fetchers were all being told to WAIT by the MergeManager but no merge was > taking place. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira