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https://issues.apache.org/jira/browse/HDFS-814?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Hairong Kuang updated HDFS-814:
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    Attachment: getLength-yahoo-0.20.patch

This patch allows a user to get a file's length from DFSOutputStream in 0.20. 
If a user needs to open a file and fetch its length, it could do it in one RPC 
with this patch so reducing one getFileStatus call. Different from the same API 
in 0.20, The return value of getVisibleLength() always the same as the meta 
info stored in NameNode's memory while the file is opened.

> 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: getLength-yahoo-0.20.patch, h814_20091221.patch, 
> h814_20091221_0.21.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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