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From "Eric Payne (JIRA)" <j...@apache.org>
Subject [jira] [Created] (YARN-2592) Preemption can kill containers to fulfil need of already over-capacity queue.
Date Tue, 23 Sep 2014 22:20:33 GMT
Eric Payne created YARN-2592:
--------------------------------

             Summary: Preemption can kill containers to fulfil need of already over-capacity
queue.
                 Key: YARN-2592
                 URL: https://issues.apache.org/jira/browse/YARN-2592
             Project: Hadoop YARN
          Issue Type: Bug
    Affects Versions: 2.5.1, 3.0.0
            Reporter: Eric Payne


There are scenarios in which one over-capacity queue can cause preemption of another over-capacity
queue. However, since killing containers may lose work, it doesn't make sense to me to kill
containers to feed an already over-capacity queue.

Consider the following:

{code}
root has A,B,C, total capacity = 90
A.guaranteed = 30, A.pending = 5, A.current = 40
B.guaranteed = 30, B.pending = 0, B.current = 50
C.guaranteed = 30, C.pending = 0, C.current = 0
{code}

In this case, the queue preemption monitor will kill 5 resources from queue B so that queue
A can pick them up, even though queue A is already over its capacity. This could lose any
work that those containers in B had already done.

Is there a use case for this behavior? It seems to me that if a queue is already over its
capacity, it shouldn't destroy the work of other queues. If the over-capacity queue needs
more resources, that seems to be a problem that should be solved by increasing its guarantee.



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