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From "Nicolas Liochon (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-11492) The servers do not honnor the tcpNoDelay option
Date Thu, 10 Jul 2014 15:27:05 GMT
Nicolas Liochon created HBASE-11492:
---------------------------------------

             Summary: The servers do not honnor the tcpNoDelay option
                 Key: HBASE-11492
                 URL: https://issues.apache.org/jira/browse/HBASE-11492
             Project: HBase
          Issue Type: Bug
          Components: regionserver
    Affects Versions: 0.96.0, 0.98.0, 0.99.0
            Reporter: Nicolas Liochon
            Priority: Critical
             Fix For: 0.99.0, 0.98.5


There is an option to set tcpNoDelay, defaulted to true, but the socket channel is actually
not changed. As a consequence, the server works with nagle enabled. This leads to very degraded
behavior when a single connection is shared between threads. We enter into conflicts with
nagle and tcp delayed ack. 

Here is an example of performance with the PE tool plus HBASE-11491:
{noformat}
oneCon     #client       sleep          exeTime (seconds)                             avg
latency, sleep excluded (microseconds)
true           1               0                31                                       
             310
false          1               0                31                                       
             310
true           2               0                50                                       
              500
false          2               0               31                                        
             310
true           2                5               488 (including 200s sleeping)            
  2880 
false          2               5               246  (including 200s sleeping)            
  460
{noformat}

The latency is divided by 5 when the connection is shared. This is the delayed ack kicking
in. This can be fixed by really using tcp no delay.





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