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From "Naganarasimha G R (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-4606) CapacityScheduler: applications could get starved because computation of #activeUsers considers pending apps
Date Wed, 20 Jan 2016 09:22:39 GMT

    [ https://issues.apache.org/jira/browse/YARN-4606?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15108267#comment-15108267
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Naganarasimha G R commented on YARN-4606:
-----------------------------------------

Hi [~wangda],
Thanks for sharing the proposal, Just to clarify whether my understanding is correct : 
* While calculating user limit for assigning containers to a app we take the #activeusers
= #users who have apps in activated stage and has outstanding requests. 
* And while calculating userAMlimit for activating a app we take #activeusers = #unique users
who are having apps in the pending order policy?
 

> CapacityScheduler: applications could get starved because computation of #activeUsers
considers pending apps 
> -------------------------------------------------------------------------------------------------------------
>
>                 Key: YARN-4606
>                 URL: https://issues.apache.org/jira/browse/YARN-4606
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: capacity scheduler, capacityscheduler
>    Affects Versions: 2.8.0, 2.7.1
>            Reporter: Karam Singh
>            Assignee: Wangda Tan
>            Priority: Critical
>
> Currently, if all applications belong to same user in LeafQueue are pending (caused by
max-am-percent, etc.), ActiveUsersManager still considers the user is an active user. This
could lead to starvation of active applications, for example:
> - App1(belongs to user1)/app2(belongs to user2) are active, app3(belongs to user3)/app4(belongs
to user4) are pending
> - ActiveUsersManager returns #active-users=4
> - However, there're only two users (user1/user2) are able to allocate new resources.
So computed user-limit-resource could be lower than expected.



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