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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-814) Add an api to get the visible length of a DFSDataInputStream.
Date Tue, 22 Dec 2009 18:52:29 GMT

    [ https://issues.apache.org/jira/browse/HDFS-814?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12793728#action_12793728
] 

dhruba borthakur commented on HDFS-814:
---------------------------------------

Code looks good. Can we also enhance DFSClient.getFileInfo() to return the current length
of a file (for a file that is being written into)... something like this:

{quote}
 
  public FileStatus getFileInfo(String src) throws IOException {
    checkOpen();
    try {
      FileStatus stat = namenode.getFileInfo(src);
      if (stat.isUnderConstruction()) {
        stat.length = DFSClient.open(src).getFileLength();
      }
    } catch(RemoteException re) {
      throw re.unwrapRemoteException(AccessControlException.class);
    }
  }

{quote}

The benefit of this approach might reduce confusion to users...especially if DFSClient.getFileInfo()
and DfsClient.getFileLength() returns different file sizes for the same file. Also, I am guessing
that this will not introduce any new performance impact.

> Add an api to get the visible length of a DFSDataInputStream.
> -------------------------------------------------------------
>
>                 Key: HDFS-814
>                 URL: https://issues.apache.org/jira/browse/HDFS-814
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>          Components: hdfs client
>            Reporter: Tsz Wo (Nicholas), SZE
>            Assignee: Tsz Wo (Nicholas), SZE
>             Fix For: 0.21.0, 0.22.0
>
>         Attachments: h814_20091221.patch
>
>
> Hflush guarantees that the bytes written before are visible to the new readers.  However,
there is no way to get the length of the visible bytes.  The visible length is useful in some
applications like SequenceFile.

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