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https://issues.apache.org/jira/browse/YARN-3633?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14609278#comment-14609278
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Arun Suresh commented on YARN-3633:
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I guess the line that was introduced needs to be synchronized (guess we need to
do the same for {{removeApp}} where we are subtracting).. given that you are
adding/subtracting from "totalAmResourceUsage" defined in the
{{FairScheduler}}.. and considering that the {{Resources#addTo/subtractFrom}}
actually performs a get and set (and the value can change in between if some
other AM is added/removed.. possibly during a concurrently running continuous
scheduling attempt)
> 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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