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From "Kihwal Lee (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2071) Use of isConnected() in DataXceiver is invalid
Date Wed, 15 Jun 2011 18:36:48 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2071?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13049946#comment-13049946
] 

Kihwal Lee commented on HDFS-2071:
----------------------------------

The system functions without patch with almost no noticeable timing difference.
No test is added since the correctness cannot be checked by running tests.

> 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
>            Assignee: Kihwal Lee
>            Priority: Minor
>             Fix For: 0.20.3
>
>         Attachments: HDFS-2071.patch
>
>
> 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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