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From "Carlo Curino (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-2022) Preempting an Application Master container can be kept as least priority when multiple applications are marked for preemption by ProportionalCapacityPreemptionPolicy
Date Mon, 12 May 2014 09:25:16 GMT

    [ https://issues.apache.org/jira/browse/YARN-2022?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13994957#comment-13994957
] 

Carlo Curino commented on YARN-2022:
------------------------------------

Sunil, I am travelling abroad till 26th (please forgive delays)... I could only skim the patch
from a mobile device. It looks reasonable, a concern I have is that we rely on a user set
Priority to choose whether to preempt or not. Unless there are check in place preventing the
user from abusing this value, this is egregiously gameable (set my containers all to AM priority
and get away with murder).

Also I thought more about the possible corner cases, after conversation with Chris Douglas,
and Mayank: we should keep an eye out for max percentage of resources dedicated to AMs...
we should "save" the AMs from earlier (higher-pri) applications up till the max % of AM we
can allocate in the Queue, and at the very least not "protect" the AMs past that point. Similar
check should be in place for userLimitFactor. Without this it is entirely possible that a
queue is wedged with 100% AMs or that a user has in its AM more resources than he deserve
(and it is systematically skipped, even if the cluster is empty). We have seen some of this
in particular extreme test cases (espilon-size queues, many apps "moved" to a queue etc...).
Please share your thoughts on this... 

> Preempting an Application Master container can be kept as least priority when multiple
applications are marked for preemption by ProportionalCapacityPreemptionPolicy
> ---------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: YARN-2022
>                 URL: https://issues.apache.org/jira/browse/YARN-2022
>             Project: Hadoop YARN
>          Issue Type: Improvement
>          Components: resourcemanager
>    Affects Versions: 2.4.0
>            Reporter: Sunil G
>            Assignee: Sunil G
>         Attachments: Yarn-2022.1.patch
>
>
> Cluster Size = 16GB [2NM's]
> Queue A Capacity = 50%
> Queue B Capacity = 50%
> Consider there are 3 applications running in Queue A which has taken the full cluster
capacity. 
> J1 = 2GB AM + 1GB * 4 Maps
> J2 = 2GB AM + 1GB * 4 Maps
> J3 = 2GB AM + 1GB * 2 Maps
> Another Job J4 is submitted in Queue B [J4 needs a 2GB AM + 1GB * 2 Maps ].
> Currently in this scenario, Jobs J3 will get killed including its AM.
> It is better if AM can be given least priority among multiple applications. In this same
scenario, map tasks from J3 and J2 can be preempted.
> Later when cluster is free, maps can be allocated to these Jobs.



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