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https://issues.apache.org/jira/browse/HADOOP-894?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12494580
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Konstantin Shvachko commented on HADOOP-894:
--------------------------------------------

Summarizing:
- LocatedBlocks open(String src);
- LocatedBlocks getBlockLocations(String file, long start, long length);
- open() always returns first 10 blocks as decided by the name-node.

Does that work for everybody?

> dfs client protocol should allow asking for parts of the block map
> ------------------------------------------------------------------
>
>                 Key: HADOOP-894
>                 URL: https://issues.apache.org/jira/browse/HADOOP-894
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: dfs
>            Reporter: Owen O'Malley
>         Assigned To: Konstantin Shvachko
>         Attachments: partialBlockList.patch, partialBlockList2.patch
>
>
> I think that the HDFS client protocol should change like:
> /** The meta-data about a file that was opened. */
> class OpenFileInfo {
>   /** the info for the first block */
>   public LocatedBlockInfo getBlockInfo();
>   public long getBlockSize();
>   public long getLength();
> }
> interface ClientProtocol extends VersionedProtocol {
>   public OpenFileInfo open(String name) throws IOException;
>   /** get block info for any range of blocks */
>   public LocatedBlockInfo[] getBlockInfo(String name, int blockOffset, int 
> blockLength) throws IOException;
> }
> so that the client can decide how much block info to request and when. 
> Currently, when the file is opened or an error occurs, the entire block list 
> is requested and sent.

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