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From "Kihwal Lee (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-2071) Use of isConnected() in DataXceiver is invalid
Date Mon, 13 Jun 2011 14:37:51 GMT
Use of isConnected() in DataXceiver is invalid

                 Key: HDFS-2071
                 URL: https://issues.apache.org/jira/browse/HDFS-2071
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: data-node
    Affects Versions: 0.23.0
            Reporter: Kihwal Lee
            Priority: Minor

The use of Socket.isConnected() in DataXceiver.run() is not valid. It returns false until
the connection is made and then always returns true after that. It will never return false
after the initial connection is successfully made. Socket.isClosed() or SocketChannel.isOpen()
should be used instead, assuming someone is handling SocketException and does Socket.close()
or SocketChannel.close(). It seems the op handlers in DataXceiver are diligently using IOUtils.closeStream(),
which will invoke SocketChannel.close().

- } while (s.isConnected() && socketKeepaliveTimeout > 0);
+ } while (!s.isClosed() && socketKeepaliveTimeout > 0);

The effect of this bug is very minor, as the socket is read again right after. If the connection
was closed, the readOp() will throw an EOFException, which is caught and dealt with properly.
 The system still functions normally with probably only few microseconds of extra overhead
in the premature connection closure cases.

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