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From "Naganarasimha G R (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-6749) MR AM should reuse containers for Map/Reduce Tasks
Date Thu, 13 Oct 2016 20:45:20 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-6749?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15573131#comment-15573131
] 

Naganarasimha G R commented on MAPREDUCE-6749:
----------------------------------------------

Hi [~devaraj.k],
Thanks for the detailed explanation As it would involve considerable modifications and changes
in core code, hope we can create a new branch and get the things in there so that its easier
for others to have a look before it gets into the trunk or main stream branches

bq. I think the limit configuration for no of map/reduce reuse containers would allow other
applications to start running without waiting for the Job to be finished when reuse is enabled.
If there is a big Job running which could occupy the entire cluster, and then any high priority
application gets submitted this limit for maps/reduce container would probably give a room
for high priority application to start running without preempting the containers of the previous
Job. By default there is no limit for number of containers to be reused and if any user/Job
wanted to have this constraint they can configure it.
Yes i understand it thanks for the explanation, but issue would be how the application knows
whats the right configuration for these, in application per se they would think it would be
always right to run all the tasks in the given container than launching more containers. If
there was a way for admin to enforce it it would be usefull. If its just client level configuration
it just adds into already long list of configurations and users will not be clear what to
configure for it. And besides would it be better to have just how many tasks can reuse a given
container and try to avoid for Map and Reduce seperately ?

Btw it could be also good to introduce a metric for number of Map Tasks or Reduce tasks which
has reused the containers

bq. If you want to have a try this feature, you can apply MAPREDUCE-6773, MAPREDUCE-6781,
MAPREDUCE-6784, MAPREDUCE-6785, MAPREDUCE-6786 and then try this feature. 
Sure Deva will try it over the weekend and update you, anyway started to take look at them

bq. Here we should note that the whole container log which is displaying for TaskAttempt is
not applicable to the TaskAttempt and the log can be identified easily which part applicable
to it.
This was the problem which we generally faced and difficult for the customers to understand
that entire log is not for the task attempt, so was wondering to have any better approach
to this. 








> MR AM should reuse containers for Map/Reduce Tasks
> --------------------------------------------------
>
>                 Key: MAPREDUCE-6749
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-6749
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: applicationmaster, mrv2
>            Reporter: Devaraj K
>            Assignee: Devaraj K
>         Attachments: MAPREDUCE-6749-Container Reuse-v0.pdf
>
>
> It is with the continuation of MAPREDUCE-3902, MR AM should reuse containers for Map/Reduce
Tasks similar to the JVM Reuse feature we had in MRv1.



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