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https://issues.apache.org/jira/browse/HDFS-814?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12793818#action_12793818
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Tsz Wo (Nicholas), SZE commented on HDFS-814:
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> an we also enhance DFSClient.getFileInfo() to return the current length of a
> file (for a file that is being written into)...
I think it may be a good idea to change DFSClient.getFileInfo(). But we cannot
easily update stat.length since there is no api to update the length in
FileStatus.
> 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.
There is no such method called DfsClient.getFileLength(). Do you mean
DfsClient.DFSInputStream.getFileLength()? This method is not visible since
DfsClient.DFSInputStream is package private (and I change it to private in my
patch).
For the performance, it is hard to estimate since there are two additional
round trips (one to the NN and one to a DN) for DFSClient.open(..).
> 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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