[
https://issues.apache.org/jira/browse/MAPREDUCE-4228?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13269155#comment-13269155
]
alex gemini commented on MAPREDUCE-4228:
----------------------------------------
It's a little confusing,if mapreduce.job.reduce.slowstart.completedmaps didn't
control when reduce will start scheduling,should we just remove this parameter?
or maybe change name to mapreduce.job.reduce.slowstart.startedmaps?
> 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
>
> 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.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators:
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira
