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From "Szilard Nemeth (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-8951) Defining default queue placement rule in allocations file with create="false" throws an NPE
Date Mon, 29 Oct 2018 12:34:08 GMT

    [ https://issues.apache.org/jira/browse/YARN-8951?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16667131#comment-16667131
] 

Szilard Nemeth commented on YARN-8951:
--------------------------------------

See the attached patch for a testcase that reproduces the issue.

> Defining default queue placement rule in allocations file with create="false" throws
an NPE
> -------------------------------------------------------------------------------------------
>
>                 Key: YARN-8951
>                 URL: https://issues.apache.org/jira/browse/YARN-8951
>             Project: Hadoop YARN
>          Issue Type: Bug
>            Reporter: Szilard Nemeth
>            Assignee: Szilard Nemeth
>            Priority: Major
>         Attachments: default-placement-rule-with-create-false.patch
>
>
> If the default queue placement rule is defined with {{create="false"}} and a scheduling
request is created for queue {{"root.default"}}, then {{FairScheduler#assignToQueue}} throws
an NPE, while trying to construct an error message in the catch block of {{IllegalStateException}},
relying on the fact that the {{rmApp}} is not null but it is.
> Example of such a config file:
> {code:java}
> <?xml version="1.0"?>
> <allocations>
> 	<queue name="parentq" type="parent">
> 		<minResources>1024mb,0vcores</minResources>
> 	</queue>
> 	<queuePlacementPolicy>
> 		<rule name="default" create="false"/>
> 	</queuePlacementPolicy>
> </allocations>
> {code}
> This is suspicious, as there are some null checks for {{rmApp}} in the same method.
>  Not sure if this is a special case for the tests or it is reproducable in a cluster,
this needs further investigation.
> In any case, it's not good that we try to dereference the {{rmApp}} that is null.
> On the other hand, I'm not sure if the default queue placement rule with {{create="false"}} makes
sense at all. Looking at the documentation ([https://hadoop.apache.org/docs/r3.1.0/hadoop-yarn/hadoop-yarn-site/FairScheduler.html):]
> {quote}default: the app is placed into the queue specified in the ‘queue’ attribute
of the default rule. *If ‘queue’ attribute is not specified, the app is placed into ‘root.default’
queue.*
> A queuePlacementPolicy element: which contains a list of rule elements that tell the
scheduler how to place incoming apps into queues. Rules are applied in the order that they
are listed. Rules may take arguments. *All rules accept the “create” argument, which indicates
whether the rule can create a new queue. “Create” defaults to true; if set to false and
the rule would place the app in a queue that is not configured in the allocations file, we
continue on to the next rule.* The last rule must be one that can never issue a continue....
> {quote}
> In this case, the rule has the queue property suppressed so the apps should be placed
to the {{root.default}} queue (which is an undefined queue according to the config file),
and create is false, meaning that the queue {{root.default}} cannot be created at all.
> *This seems to be a case of an invalid queue configuration file for me.*
> [~jlowe], [~leftnoteasy]: What is your take on this?
>  



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