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https://issues.apache.org/jira/browse/YARN-4606?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16459882#comment-16459882
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Manikandan R commented on YARN-4606:
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Attaching .001 patch containing test case for CS and changes required to fix
the problem (activeUsersOfPendingApps being-ve issue) mentioned in my previous
comment. Also, tested the patch in my pseudo setup for CS. I am planning to run
all junits after the review.
{quote}AppSchedulingInfo is supports to cache status for pending resource, it
might be better to avoid invoking SchedulerAppAttempt's method from
AppSchedulingInfo.{quote}
[~leftnoteasy] As of now, {{AppSchedulingInfo}} calls only
{{SchedulerAppAttempt#isWaitingForAMContainer}} to take some decision, for
which I don't see any cache. Can you please explain?
> 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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