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From "Daryn Sharp (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HADOOP-14032) Reduce fair call queue priority inversion
Date Fri, 27 Jan 2017 21:26:24 GMT
Daryn Sharp created HADOOP-14032:

             Summary: Reduce fair call queue priority inversion
                 Key: HADOOP-14032
                 URL: https://issues.apache.org/jira/browse/HADOOP-14032
             Project: Hadoop Common
          Issue Type: Sub-task
          Components: ipc
    Affects Versions: 2.7.0
            Reporter: Daryn Sharp
            Assignee: Daryn Sharp

The fcq's round robin multiplexer actually rewards abusive users.  Queue consumers scan for
a call from the roving multiplexer index to the lowest prio ring before wrapping around to
the higher prio rings.

Let's take a fcq with 4 priority rings.  Multiplexer shares per index are 8, 4, 2, 1.  
All well behaved clients are operating in ring 0.  Bad client floods the server and drops
to the lowest prio.  Unfortunately the service order gives 8 shares to the good clients, followed
by 4+2+1=7 shares to the bad client.

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