Use of isConnected() in DataXceiver is invalid
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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().
{code}
- } while (s.isConnected() && socketKeepaliveTimeout > 0);
+ } while (!s.isClosed() && socketKeepaliveTimeout > 0);
{code}
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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