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From "Wangda Tan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-3243) CapacityScheduler should pass headroom from parent to children to make sure ParentQueue obey its capacity limits.
Date Thu, 30 Apr 2015 20:55:07 GMT

    [ https://issues.apache.org/jira/browse/YARN-3243?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14522241#comment-14522241

Wangda Tan commented on YARN-3243:

[~tgraves], I just merged this to branch-2.7.

> CapacityScheduler should pass headroom from parent to children to make sure ParentQueue
obey its capacity limits.
> -----------------------------------------------------------------------------------------------------------------
>                 Key: YARN-3243
>                 URL: https://issues.apache.org/jira/browse/YARN-3243
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: capacityscheduler, resourcemanager
>            Reporter: Wangda Tan
>            Assignee: Wangda Tan
>             Fix For: 2.8.0
>         Attachments: YARN-3243.1.patch, YARN-3243.2.patch, YARN-3243.3.patch, YARN-3243.4.patch,
> Now CapacityScheduler has some issues to make sure ParentQueue always obeys its capacity
limits, for example:
> 1) When allocating container of a parent queue, it will only check parentQueue.usage
< parentQueue.max. If leaf queue allocated a container.size > (parentQueue.max - parentQueue.usage),
parent queue can excess its max resource limit, as following example:
> {code}
>         A  (usage=54, max=55)
>        /     \
>       A1     A2 (usage=1, max=55)
> (usage=53, max=53)
> {code}
> Queue-A2 is able to allocate container since its usage < max, but if we do that, A's
usage can excess A.max.
> 2) When doing continous reservation check, parent queue will only tell children "you
need unreserve *some* resource, so that I will less than my maximum resource", but it will
not tell how many resource need to be unreserved. This may lead to parent queue excesses configured
maximum capacity as well.
> With YARN-3099/YARN-3124, now we have {{ResourceUsage}} class in each class, *here is
my proposal*:
> - ParentQueue will set its children's ResourceUsage.headroom, which means, *maximum resource
its children can allocate*.
> - ParentQueue will set its children's headroom to be (saying parent's name is "qA"):
min(qA.headroom, qA.max - qA.used). This will make sure qA's ancestors' capacity will be enforced
as well (qA.headroom is set by qA's parent).
> - {{needToUnReserve}} is not necessary, instead, children can get how much resource need
to be unreserved to keep its parent's resource limit.
> - More over, with this, YARN-3026 will make a clear boundary between LeafQueue and FiCaSchedulerApp,
headroom will consider user-limit, etc.

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