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From "Craig Welch (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-2008) CapacityScheduler may report incorrect queueMaxCap if there is hierarchy queue structure
Date Tue, 22 Jul 2014 20:48:39 GMT

    [ https://issues.apache.org/jira/browse/YARN-2008?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14070875#comment-14070875
] 

Craig Welch commented on YARN-2008:
-----------------------------------

[~airbots], -re

{quote}
and if the application gets the low baseline headroom it will not be able to effectively use
that greater capacity. 
{quote}

right, that's what the patch is intended to do, but the approach here is to only drop that
when needed based on utilization - when utilization is not an issue, allow the maxcapacity
logic to continue as today and let the AM use the additional available headroom 

> CapacityScheduler may report incorrect queueMaxCap if there is hierarchy queue structure

> -----------------------------------------------------------------------------------------
>
>                 Key: YARN-2008
>                 URL: https://issues.apache.org/jira/browse/YARN-2008
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>    Affects Versions: 2.3.0
>            Reporter: Chen He
>            Assignee: Craig Welch
>         Attachments: YARN-2008.1.patch, YARN-2008.2.patch
>
>
> If there are two queues, both allowed to use 100% of the actual resources in the cluster.
Q1 and Q2 currently use 50% of actual cluster's resources and there is not actual space available.
If we use current method to get headroom, CapacityScheduler thinks there are still available
resources for users in Q1 but they have been used by Q2. 
> If the CapacityScheduelr has a hierarchy queue structure, it may report incorrect queueMaxCap.
Here is a example
>                              ||                    ||rootQueue||     ||
> |  |                               /                               |                
   \                     |
> |      L1ParentQueue1                      |          |            L1ParentQueue2   
|
> |  (allowed to use up 80% of its parent)    |  |         (allowed to use 20% in minimum
of its parent)|
> |                    /   |     \ |                            |  
> |  L2LeafQueue1 |    L2LeafQueue2 |  |     
> |(50% of its parent) |  (50% of its parent in minimum) |   |
> When we calculate headroom of a user in L2LeafQueue2, current method will think L2LeafQueue2
can use 40% (80%*50%) of actual rootQueue resources. However, without checking L1ParentQueue1,
we are not sure. It is possible that L1ParentQueue2 have used 40% of rootQueue resources right
now. Actually, L2LeafQueue2 can only use 30% (60%*50%). 



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