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From "Zian Chen (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (YARN-7274) Ability to disable elasticity at leaf queue level
Date Wed, 15 Nov 2017 00:40:00 GMT

    [ https://issues.apache.org/jira/browse/YARN-7274?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16252759#comment-16252759
] 

Zian Chen edited comment on YARN-7274 at 11/15/17 12:39 AM:
------------------------------------------------------------

I investigated this issue and figured out how we could solve this issue. Basically, we have
sanity check within capacitiesSanityCheck which require capacity must be smaller than or equal
to maxCapacity.  Actually, we don't need this constraint since we want to let absolute capacity
can be equal to absolute max capacity in the extreme situation, but if we restrict the capacity
cannot be bigger than maxCapacity, we will never able to achieve absCapacity equal to absMaxCapacity
since the way to calculate absCapacity is absCap of queue x is multiple of capacity of x 
* capacity of the parent of x * ... which will make absCap of queue x always smaller than
absolute Max capacity of x. So, when we release the constriction that capacity should be smaller
than or equal to maxCapacity, we will solve this problem.  Opinions [~leftnoteasy] 


was (Author: zian chen):
I investigated this issue and figured out how we could solve this issue. Basically, we have
sanity check within capacitiesSanityCheck which require capacity must be smaller than or equal
to maxCapacity.  Actually, we don't need this constraint since we want to let absolute capacity
can be equal to absolute max capacity in the extreme situation, but if we restrict the capacity
cannot be bigger than maxCapacity, we will never able to achieve absCapacity equal to absMaxCapacity
since the way to calculate absCapacity is abs(x) = cap(x) * cap(x.parent) * ... which will
make abs(x) always smaller than absMax(x). So, when we release the constriction that capacity
should be smaller than or equal to maxCapacity, we will solve this problem.  Opinions [~leftnoteasy]


> Ability to disable elasticity at leaf queue level
> -------------------------------------------------
>
>                 Key: YARN-7274
>                 URL: https://issues.apache.org/jira/browse/YARN-7274
>             Project: Hadoop YARN
>          Issue Type: Improvement
>          Components: capacityscheduler
>            Reporter: Scott Brokaw
>            Assignee: Zian Chen
>
> The [documentation|https://hadoop.apache.org/docs/current/hadoop-yarn/hadoop-yarn-site/CapacityScheduler.html]
defines yarn.scheduler.capacity.<queue-path>.maximum-capacity as "Maximum queue capacity
in percentage (%) as a float. This limits the elasticity for applications in the queue. Defaults
to -1 which disables it."
> However, setting this value to -1 sets maximum capacity to 100% but I thought (perhaps
incorrectly) that the intention of the -1 setting is that it would disable elasticity.  This
is confirmed looking at the code:
> {code:java}
> public static final float MAXIMUM_CAPACITY_VALUE = 100;
> public static final float DEFAULT_MAXIMUM_CAPACITY_VALUE = -1.0f;
> ......
> maxCapacity = (maxCapacity == DEFAULT_MAXIMUM_CAPACITY_VALUE) ? 
> MAXIMUM_CAPACITY_VALUE : maxCapacity;
> {code}
> The sum of yarn.scheduler.capacity.<queue-path>.capacity for all queues, at each
level, must be equal to 100 but for yarn.scheduler.capacity.<queue-path>.maximum-capacity
this value is actually a percentage of the entire cluster not just the parent queue.  Yet
it can not be set lower then the leaf queue's capacity setting. This seems to make it impossible
to disable elasticity at a leaf queue level.
> This improvement is proposing that YARN have the ability to have elasticity disabled
at a leaf queue level even if a parent queue permits elasticity by having a yarn.scheduler.capacity.<queue-path>.maximum-capacity
greater then it's yarn.scheduler.capacity.<queue-path>.capacity



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