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https://issues.apache.org/jira/browse/YARN-4606?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16347209#comment-16347209
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Eric Payne commented on YARN-4606:
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Thanks everyone for the thoughtful analysis.
I am still analyzing in more depth, but I have a couple of thoughts:
{quote}this is a (known) potential issue of fair ordering policy.
{quote}
This can happen for fifo ordering policy as well.
{quote}have {{activeUsersOfPendingApps}} along with {{activeUsers}}. Hence in
case of scheduling we can depend only on {{activeUse}}
{quote}
We need to be careful with these counts because a user can have both active and
pending apps. I think the definitions should be:
- {{activeUsers}}: users that have at least one active app
- {{activeUsersOfPendingApps}}: users that have only pending apps.
> 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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