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From "Konstantinos Karanasos (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (YARN-8034) Clarification on preferredHost request with relaxedLocality
Date Sat, 17 Mar 2018 01:23:00 GMT

    [ https://issues.apache.org/jira/browse/YARN-8034?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16403185#comment-16403185
] 

Konstantinos Karanasos edited comment on YARN-8034 at 3/17/18 1:22 AM:
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Hi [~jagadish1989@gmail.com],

As [~jlowe] mentioned, this is very related to YARN-6344 for the capacity scheduler. What you
should look at is the "yarn.scheduler.capacity.rack-locality-additional-delay" parameter.

Since you have only one (or very few) container requests, the current logic (if you let the
above parameter to its default value) will lead to relaxing locality almost immediately. If
you set that parameter to a positive value, you should achieve your desired behavior.


was (Author: kkaranasos):
Hi [~jagadish1989@gmail.com],

As [~jlowe] mentioned, this is very related to YARN-6344 for the capacity scheduler. What you
should look at is the "yarn.scheduler.capacity.rack-locality-additional-delay" parameter.

Since you have only one (or very few) container requests, the current logic (if you let the
above parameter to its default value) value will lead to relaxing locality almost immediately.
If you set that parameter to a positive value, you should achieve your desired behavior.

> Clarification on preferredHost request with relaxedLocality
> -----------------------------------------------------------
>
>                 Key: YARN-8034
>                 URL: https://issues.apache.org/jira/browse/YARN-8034
>             Project: Hadoop YARN
>          Issue Type: Bug
>            Reporter: Jagadish
>            Priority: Major
>
> I work on Apache Samza, a stateful stream-processing framework that leverages Yarn for
resource management. The Samza AM requests resources on specific hosts to schedule stateful
jobs. We set relaxLocality = true in these requests we make to Yarn. Often we have observed
that we don't get containers on the hosts that we requested them on and the Yarn RM returns
containers on arbitrary hosts. 
> Do you know what the behavior of the FairScheduler/CapacityScheduler is when setting
"relaxLocality = true".I did play around by setting a high value for yarn.scheduler.capacity.node-locality-delay
but it did not seem to matter. However, when setting relaxLocality = false, we get resources
on the exact hosts we requested on.
> The behavior I want from Yarn is "Honor locality to the best possible extent and only
return a container on an arbitrary host if the requested host is down". Is there a way to
accomplish this?
> If you can point me to the Scheduler code, I'm happy to look at it as well. For context,
we have continuous scheduling enabled in our clusters.



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