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From "Wangda Tan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-4606) CapacityScheduler: applications could get starved because computation of #activeUsers considers pending apps
Date Fri, 04 May 2018 03:30:00 GMT

    [ https://issues.apache.org/jira/browse/YARN-4606?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16463324#comment-16463324
] 

Wangda Tan commented on YARN-4606:
----------------------------------

Thanks [~manirajv06@gmail.com], 
Some questions: 

1) Does this patch handles the case that one user has multiple pending apps? (Since it doesn't
store user to apps information).

2) 
{code}
abstractUsersManager.decrNumActiveUsersOfPendingApps(); 
{code}
Should we call this inside {{SchedulerApplicationAttempt#pullNewlyUpdatedContainers}}? 
I think we should remove active user from pending apps once AM container get allocated.

3)
{code} 
Resources.lessThan(rc, cr,
                metrics.getUsedAMResources(), metrics.getMaxAMResources())
{code} 
Instead of using metrics, it might be better to use {{SchedulerApplicationAttempt#getAppAttemptResourceUsage}}
instead. 

> 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: Manikandan R
>            Priority: Critical
>         Attachments: YARN-4606.001.patch, YARN-4606.1.poc.patch, YARN-4606.POC.2.patch,
YARN-4606.POC.patch
>
>
> 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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