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From "Rohit Agarwal (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-3633) With Fair Scheduler, cluster can logjam when there are too many queues
Date Wed, 13 May 2015 23:27:01 GMT

    [ https://issues.apache.org/jira/browse/YARN-3633?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14542902#comment-14542902
] 

Rohit Agarwal commented on YARN-3633:
-------------------------------------

[~sandyr] If we do that and have no cluster-wide AMShare then we may have a situation where
all queues are just running AMs - imagine lots of apps submitted at the same time to different
queues.

But yes we can use this 'max AM share applies after first AM' property instead of setting
{{maxAMShare for queue = max(0.5*fairShare, SomeMinimumSizeEnoughToRunOneContainer)}}

> 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
>
> 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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