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From "Arun Suresh (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-3633) With Fair Scheduler, cluster can logjam when there are too many queues
Date Tue, 30 Jun 2015 22:24:05 GMT

    [ https://issues.apache.org/jira/browse/YARN-3633?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14609175#comment-14609175
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Arun Suresh commented on YARN-3633:
-----------------------------------

Agreed..
So just so that Im on the same page, the {{clusterMaxAMShare}} is essentially acting as an
upper limit.. right ? Can we have the default as negative, to preserve current behavior by
default ?

Otherwise, the patch looks good.. although I feel in the {{addAMResourceUsage}}, I think we
should synchronize the part where we add the {{amResource}} to the scheduler's total am resource
usage field.
+1 after that.

> With Fair Scheduler, cluster can logjam when there are too many queues
> ----------------------------------------------------------------------
>
>                 Key: YARN-3633
>                 URL: https://issues.apache.org/jira/browse/YARN-3633
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: fairscheduler
>    Affects Versions: 2.6.0
>            Reporter: Rohit Agarwal
>            Assignee: Rohit Agarwal
>            Priority: Critical
>         Attachments: YARN-3633-1.patch, YARN-3633.patch
>
>
> It's possible to logjam a cluster by submitting many applications at once in different
queues.
> For example, let's say there is a cluster with 20GB of total memory. Let's say 4 users
submit applications at the same time. The fair share of each queue is 5GB. Let's say that
maxAMShare is 0.5. So, each queue has at most 2.5GB memory for AMs. If all the users requested
AMs of size 3GB - the cluster logjams. Nothing gets scheduled even when 20GB of resources
are available.



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