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From "Benoit Sigoure (JIRA)" <j...@apache.org>
Subject [jira] Created: (HBASE-3115) HBaseClient wastes 1 TCP packet per RPC
Date Fri, 15 Oct 2010 08:25:32 GMT
HBaseClient wastes 1 TCP packet per RPC
---------------------------------------

                 Key: HBASE-3115
                 URL: https://issues.apache.org/jira/browse/HBASE-3115
             Project: HBase
          Issue Type: Improvement
          Components: client
    Affects Versions: 0.89.20100621, 0.20.6, 0.20.5, 0.20.4, 0.20.3, 0.20.2, 0.20.1
            Reporter: Benoit Sigoure
            Priority: Minor


In {{ipc/HBaseClient.java}}, the method {{sendParam}} does:
{code}
out.writeInt(dataLength);      //first put the data length
out.write(data, 0, dataLength);//write the data
{code}
While analyzing some tcpdump traces tonight, I saw that this consistently translates to 1
TCP packet with a 4 byte payload followed by another TCP packet with the RPC itself.  This
makes inefficient use of network resources and adversely affects TCP throughput.  I believe
each of those lines translates to a {{write}} system call on the socket's file descriptor
(unnecessary system calls are also bad for performance).  The code attempts to call {{out.flush();}}
but this approach is ineffective on sockets in Java (as far as I empirically noticed over
the past few months).

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