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https://issues.apache.org/jira/browse/MAPREDUCE-4228?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13402155#comment-13402155
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Hudson commented on MAPREDUCE-4228:
-----------------------------------
Integrated in Hadoop-Hdfs-trunk #1089 (See
[https://builds.apache.org/job/Hadoop-Hdfs-trunk/1089/])
MAPREDUCE-4228. mapreduce.job.reduce.slowstart.completedmaps is not working
properly (Jason Lowe via bobby) (Revision 1354181)
Result = FAILURE
bobby : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1354181
Files :
* /hadoop/common/trunk/hadoop-mapreduce-project/CHANGES.txt
*
/hadoop/common/trunk/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/rm/RMContainerAllocator.java
*
/hadoop/common/trunk/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/TestRMContainerAllocator.java
> mapreduce.job.reduce.slowstart.completedmaps is not working properly to delay
> the scheduling of the reduce tasks
> ----------------------------------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-4228
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4228
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: applicationmaster, mrv2
> Affects Versions: 0.23.1
> Reporter: Jason Lowe
> Assignee: Jason Lowe
> Fix For: 0.23.3, 2.0.1-alpha, 3.0.0
>
> Attachments: MAPREDUCE-4228.patch, MAPREDUCE-4228.patch,
> MAPREDUCE-4228.patch
>
>
> If no more map tasks need to be scheduled but not all have completed, the
> ApplicationMaster will start scheduling reducers even if the number of
> completed maps has not met the mapreduce.job.reduce.slowstart.completedmaps
> threshold. For example, if the property is set to 1.0 all maps should
> complete before any reducers are scheduled. However the reducers are
> scheduled as soon as the last map task is assigned to a container. For a job
> with very long-running maps, a cluster with enough capacity to launch all map
> tasks could cause reducers to launch prematurely and waste cluster resources.
> Thanks to Phil Su for discovering this issue.
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