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https://issues.apache.org/jira/browse/YARN-4606?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16443176#comment-16443176
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Eric Payne commented on YARN-4606:
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[[email protected]], I am attaching {{YARN-4606.POC.2.patch}} that 
demonstrates what I am suggesting. I have teste4d it in my pseudo cluster and 
it will only activate a new AM if the used queue AM resources are less than the 
queue max AM resources, but it also fixes the problem of starvation.

I have only tested this on Capacity Scheduler, not Fair Scheduler.

> 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, 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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