[jira] [Commented] (YARN-4606) CapacityScheduler: applications could get starved because computation of #activeUsers considers pending apps

["Wangda Tan (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/YARN-4606?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16286883#comment-16286883 ] 

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

[~jlowe], as we discussed offline, this is a (known) potential issue of fair ordering policy. Please let me know if you have any thoughts on this.

> 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
>         Attachments: YARN-4606.1.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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