[
https://issues.apache.org/jira/browse/HADOOP-3940?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Chris Douglas updated HADOOP-3940:
----------------------------------
Attachment: 3940-0.patch
Simplest fix, waiting on numRequiredMapOutputs == 0.
Initializing numRequiredMapOutputs to Integer.MAX_VALUE would require a
different check at the end; this should handle both.
> Reduce often attempts in memory merge with no work
> --------------------------------------------------
>
> Key: HADOOP-3940
> URL: https://issues.apache.org/jira/browse/HADOOP-3940
> Project: Hadoop Core
> Issue Type: Bug
> Components: mapred
> Reporter: Chris Douglas
> Priority: Minor
> Attachments: 3940-0.patch
>
>
> ReduceTask.ReduceCopier.ShuffleRamManager initializes numRequiredMapOutputs
> to 0, so one of the predicates in ShuffleRamManager::waitForDataToMerge,
> {{numPendingRequests < numRequiredMapOutputs}}, is false until the first map
> output is fetched and false again after the last map output is fetched. The
> InMemFSMergeThread thread will loop busily in this state.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
