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Alejandro Abdelnur commented on MAPREDUCE-4842: ----------------------------------------------- Jason, thanks for the detailed explanation. On the degradation, maybe it would be a point to look at Asokan's approach to see if it is correct and if does not impact the performance, what do you think? > 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: Jason Lowe > Priority: Blocker > Attachments: 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