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From "Szilard Nemeth (JIRA)" <j...@apache.org>
Subject [jira] [Created] (YARN-8951) Defining default queue placement rule in allocations file with create="false" throws an NPE
Date Mon, 29 Oct 2018 12:34:07 GMT
Szilard Nemeth created YARN-8951:

             Summary: 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
         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:
<?xml version="1.0"?>
	<queue name="parentq" type="parent">
		<rule name="default" create="false"/>
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’

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....
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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