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https://issues.apache.org/jira/browse/YARN-807?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14090447#comment-14090447
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Sandy Ryza commented on YARN-807:
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I just remembered a couple reasons why it's important that we go through the
scheduler:
* *Getting all the apps underneath a parent queue* - the scheduler holds queue
hierarchy information that allows us to return applications in all leaf queues
underneath a parent queue.
* *Alisases* - In the Fair Scheduler, "default" is shorthand for
"root.default", so querying on either of these names should return applications
in that queue.
I'm open to approaches that don't require going through the scheduler, but I
think we should make sure they keep supporting these capabilities.
> When querying apps by queue, iterating over all apps is inefficient and
> limiting
> ---------------------------------------------------------------------------------
>
> Key: YARN-807
> URL: https://issues.apache.org/jira/browse/YARN-807
> Project: Hadoop YARN
> Issue Type: Improvement
> Affects Versions: 2.0.4-alpha
> Reporter: Sandy Ryza
> Assignee: Sandy Ryza
> Fix For: 2.3.0
>
> Attachments: YARN-807-1.patch, YARN-807-2.patch, YARN-807-3.patch,
> YARN-807-4.patch, YARN-807.patch
>
>
> The question "which apps are in queue x" can be asked via the RM REST APIs,
> through the ClientRMService, and through the command line. In all these
> cases, the question is answered by scanning through every RMApp and filtering
> by the app's queue name.
> All schedulers maintain a mapping of queues to applications. I think it
> would make more sense to ask the schedulers which applications are in a given
> queue. This is what was done in MR1. This would also have the advantage of
> allowing a parent queue to return all the applications on leaf queues under
> it, and allow queue name aliases, as in the way that "root.default" and
> "default" refer to the same queue in the fair scheduler.
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