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https://issues.apache.org/jira/browse/HADOOP-4178?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12634755#action_12634755
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Sreekanth Ramakrishnan commented on HADOOP-4178:
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The check we are doing should exist, for one reason which I see, capacity for
queue is configured and user specifies it as negative. In that case user has
specified a wrong capacity, user has option of specifying only positive
non-zero values. The -1 is passed by the system and it is private and internal.
I don't think it is a good idea for us to allow user to define negative
capacities.
In my opinion the checks should always be present, but the question is what
should be the fail over mechanism, should we pass on default value or should we
throw and exception and stop the JT. I think we should do checks log.warn the
negative values Log.Warn the errors and continue processing as we now have
defaults configured for these values.
With respect to computation calculation one place which I can see where
rounding errors can possibly happen is as follows : 3 queues with no GC
configured.
So values for GC would be 33, 33, 33 (this would mean 1% capacity not used).
Or case where 75% is to be allocated to 4 queues. You get 19 and 4 * 19 = 76
over allocation
With respect to testGCAllocationToQueues: the 25% is allocated to default you
have remaining 75% to be allocated to the 4 queues. So 75/4 = 18.75. Eighteen
is rounded up to 19. And not all queue can have 19 as capacity, since we are
internally balancing and computing the capacity so that it does not exceed more
than 100, One of the queues would get 18.
> The capacity scheduler's defaults for queues should be configurable.
> --------------------------------------------------------------------
>
> Key: HADOOP-4178
> URL: https://issues.apache.org/jira/browse/HADOOP-4178
> Project: Hadoop Core
> Issue Type: Improvement
> Components: contrib/capacity-sched
> Affects Versions: 0.19.0
> Reporter: Owen O'Malley
> Assignee: Sreekanth Ramakrishnan
> Priority: Blocker
> Fix For: 0.19.0
>
> Attachments: HADOOP-4178-1.patch, HADOOP-4178-2.patch,
> HADOOP-4178-3.patch, HADOOP-4178-4.patch
>
>
> The default values for the queue attributes should be configurable rather
> than hard coded.
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