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From "Craig Welch (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-1198) Capacity Scheduler headroom calculation does not work as expected
Date Wed, 01 Oct 2014 23:18:35 GMT

    [ https://issues.apache.org/jira/browse/YARN-1198?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14155764#comment-14155764

Craig Welch commented on YARN-1198:

[~john.jian.fang] I look a look at implementing the change with the tweaked .7 approach per
your suggestion above and it seemed to just be trading some complexities for others, so I
set it aside and I think the current .7 approach is as good as any.  I uploaded a .10 patch
which is the .7 fixed to apply cleanly to current trunk (.7 no longer quite does for me).
 I took a look at incorporating [YARN-1857] into this change but chose not to, as I think
they should be committed independently.  The .10 (.7) patch factors the change for [YARN-1857]
up into a different method, getHeadroom(), if you replace it with the below:

private Resource getHeadroom(User user, Resource queueMaxCap,
      Resource clusterResource, Resource userLimit) {
    Resource headroom = 
      Resources.min(resourceCalculator, clusterResource,
            Resources.min(resourceCalculator, clusterResource, 
                userLimit, queueMaxCap), 
        Resources.subtract(queueMaxCap, usedResources));
    return headroom;
then you should have the combined logic.  Note, the LeafQueue tests will then not all pass,
I believe because results changed when that patch was applied - I've not before tried the
two in combination, assuming we would apply one at a time, and then address the impact on
the other.

> Capacity Scheduler headroom calculation does not work as expected
> -----------------------------------------------------------------
>                 Key: YARN-1198
>                 URL: https://issues.apache.org/jira/browse/YARN-1198
>             Project: Hadoop YARN
>          Issue Type: Bug
>            Reporter: Omkar Vinit Joshi
>            Assignee: Craig Welch
>         Attachments: YARN-1198.1.patch, YARN-1198.10.patch, YARN-1198.2.patch, YARN-1198.3.patch,
YARN-1198.4.patch, YARN-1198.5.patch, YARN-1198.6.patch, YARN-1198.7.patch, YARN-1198.8.patch,
> Today headroom calculation (for the app) takes place only when
> * New node is added/removed from the cluster
> * New container is getting assigned to the application.
> However there are potentially lot of situations which are not considered for this calculation
> * If a container finishes then headroom for that application will change and should be
notified to the AM accordingly.
> * If a single user has submitted multiple applications (app1 and app2) to the same queue
> ** If app1's container finishes then not only app1's but also app2's AM should be notified
about the change in headroom.
> ** Similarly if a container is assigned to any applications app1/app2 then both AM should
be notified about their headroom.
> ** To simplify the whole communication process it is ideal to keep headroom per User
per LeafQueue so that everyone gets the same picture (apps belonging to same user and submitted
in same queue).
> * If a new user submits an application to the queue then all applications submitted by
all users in that queue should be notified of the headroom change.
> * Also today headroom is an absolute number ( I think it should be normalized but then
this is going to be not backward compatible..)
> * Also  when admin user refreshes queue headroom has to be updated.
> These all are the potential bugs in headroom calculations

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