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From "Wangda Tan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-4257) Move scheduler validateConf method to AbstractYarnScheduler and make it protected
Date Tue, 29 Dec 2015 23:23:49 GMT

    [ https://issues.apache.org/jira/browse/YARN-4257?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15074422#comment-15074422

Wangda Tan commented on YARN-4257:

Thanks [~kasha]/[~rhaase], 0 resource makes sense to me if container is just a pack resources
and could be delegated to other processes. (Llama or YARN-1408).

After YARN-1408, we can relax 0 resource limits for all schedulers. I agree that we can keep
validateConf as-is, each scheduler keeps own criteria about 0 resources. From my side, I still
want CS checks 0 resource, since 0 mem container will be killed immediately and 0 vcore container
doesn't sound correct in semantic (now we have to launch a process for each container, a process
cannot use 0 vcores).


> Move scheduler validateConf method to AbstractYarnScheduler and make it protected
> ---------------------------------------------------------------------------------
>                 Key: YARN-4257
>                 URL: https://issues.apache.org/jira/browse/YARN-4257
>             Project: Hadoop YARN
>          Issue Type: Improvement
>          Components: scheduler
>            Reporter: Swapnil Daingade
>            Assignee: Rich Haase
>              Labels: easyfix
>         Attachments: YARN-4257.patch
> Currently FairScheduler, CapacityScheduler and FifoScheduler each have a method private
void validateConf(Configuration conf).
> All three methods validate the minimum and maximum scheduler allocations for cpu and
memory (with minor difference). FairScheduler supports 0 as minimum allocation for cpu and
memory, while CapacityScheduler and FifoScheduler do not. We can move this code to AbstractYarnScheduler
(avoids code duplication) and make it protected for individual schedulers to override.
> Why do we care about a minimum allocation of 0 for cpu and memory?
> We contribute to a project called Apache Myriad that run yarn on mesos. Myriad supports
a feature call fine grained scaling (fgs). In fgs, a NM is launched with zero capacity (0
cpu and 0 mem). When a yarn container is to be run on the NM, a mesos offer for that node
is accepted and the NM capacity is dynamically scaled up to match the accepted mesos offer.
On completion of the yarn container, resources are returned back to Mesos and the NM capacity
is scaled down back to zero (cpu & mem). 
> In ResourceTrackerService.registerNodeManager, yarn checks if the NM capacity is at-least
as much as yarn.scheduler.minimum-allocation-mb and yarn.scheduler.minimum-allocation-vcores.
These values can be set to 0 in yarn-site.xml (so a zero capacity NM is possible). However,
the validateConf methods in CapacityScheduler and FifoScheduler do not allow for 0 values
for these properties (The FairScheduler one does allow for 0). This behaviour should be consistent
or at-least be override able.

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