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Date: Wed, 15 Jun 2011 19:24:47 +0000 (UTC)
From: "Harsh J (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Commented] (HDFS-2071) Use of isConnected() in DataXceiver
 is invalid
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    [ https://issues.apache.org/jira/browse/HDFS-2071?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13049968#comment-13049968 ] 

Harsh J commented on HDFS-2071:
-------------------------------

Gah, missed that, and the comments there. I take back my suggestion :-)

> 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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