[jira] Commented: (MAPREDUCE-1859) maxConcurrentMapTask & maxConcurrentReduceTask per job

["Owen O'Malley (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAPREDUCE-1859?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12877863#action_12877863 ] 

Owen O'Malley commented on MAPREDUCE-1859:
------------------------------------------

Putting in per-job limits on number of tasks is relatively fraught with errors and only works if you have exactly one job that *ever* pulls from the database. In the Capacity scheduler, you can set a max size for a given queue. That is at least closer to the right semantics so that you can say that any job using the database needs to use the DB queue.

> maxConcurrentMapTask & maxConcurrentReduceTask per job
> ------------------------------------------------------
>
>                 Key: MAPREDUCE-1859
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1859
>             Project: Hadoop Map/Reduce
>          Issue Type: New Feature
>          Components: job submission
>    Affects Versions: 0.20.2
>            Reporter: Johannes Zillmann
>
> It would be valuable if one could specify the max number of map/reduce slots which should be used for a given job. An example would be an map-reduce job importing from a database where you don't want 50 map tasks querying one db at a time but also you don't want to shrink the overall map task count.
> Also this is probably already possible through Fair/Capacity-Scheduler or an own Extension i think it would be a good addition for the default TaskScheduler since this seems to be more then a rare used feature.
> This would have the benefit in situations where you don't have control/ownership over the cluster as well. 
> And its more job-centric whereas the existing scheduler extensions seems to be more job-type-centric.
> Implementing this feature should be relatively straightforward. Adding something like jobConf.setMaxConcurrentMapTask(int) and respecting this configuration in JobQueueTaskScheduler.
> Not sure if this feature would be harmonical with the existing Fair/Capacity-Schedulers.

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.