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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HDFS-570) When opening a file for read, make the file length avaliable to client.
Date Fri, 28 Aug 2009 21:53:32 GMT

     [ https://issues.apache.org/jira/browse/HDFS-570?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Tsz Wo (Nicholas), SZE updated HDFS-570:
----------------------------------------

    Description: 
In order to support read consistency, DFSClient needs the file length at the file opening
time.  In the current implmentation, DFSClient obtains the file length at the file opening
time but the length is inaccurate if the file is being written.

For more details, see Section 4 in the [append design doc|https://issues.apache.org/jira/secure/attachment/12415768/appendDesign2.pdf].

  was:
In order to support read consistency, DFSClient needs the file length at the file opening
time.

For more details, see Section 4 in the [append design doc|https://issues.apache.org/jira/secure/attachment/12415768/appendDesign2.pdf].


In order to support reading a file when it is being written.  I suggest to have the following
changes:
- DFSClient obtains all the block lengths from the namenode for the blocks is not under construction.
 Note that only the last block is possibly under construction.  Other blocks must be finalized.
- For the last block, if it is under construction, DFSClient obtains the block length from
one of the datanode.

> When opening a file for read, make the file length avaliable to client.
> -----------------------------------------------------------------------
>
>                 Key: HDFS-570
>                 URL: https://issues.apache.org/jira/browse/HDFS-570
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: hdfs client
>    Affects Versions: Append Branch
>            Reporter: Tsz Wo (Nicholas), SZE
>            Assignee: Tsz Wo (Nicholas), SZE
>             Fix For: Append Branch
>
>
> In order to support read consistency, DFSClient needs the file length at the file opening
time.  In the current implmentation, DFSClient obtains the file length at the file opening
time but the length is inaccurate if the file is being written.
> For more details, see Section 4 in the [append design doc|https://issues.apache.org/jira/secure/attachment/12415768/appendDesign2.pdf].

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