[ http://issues.apache.org/jira/browse/HADOOP-170?page=all ]
Konstantin Shvachko updated HADOOP-170:
---------------------------------------
Attachment: setReplication.patch
Java documentation is added for new public methods.
> setReplication and related bug fixes
> ------------------------------------
>
> Key: HADOOP-170
> URL: http://issues.apache.org/jira/browse/HADOOP-170
> Project: Hadoop
> Type: Improvement
> Components: fs, dfs
> Versions: 0.1.1
> Reporter: Konstantin Shvachko
> Assignee: Konstantin Shvachko
> Attachments: setReplication.patch
>
> Having variable replication (HADOOP-51) it is natural to be able to
> change replication for existing files. This patch introduces the
> functionality.
> Here is a detailed list of issues addressed by the patch.
> 1) setReplication() and getReplication() methods are implemented.
> 2) DFSShell prints file replication for any listed file.
> 3) Bug fix. FSDirectory.delete() logs delete operation even if it is not
> successful.
> 4) Bug fix. This is a distributed bug.
> Suppose that file replication is 3, and a client reduces it to 1.
> Two data nodes will be chosen to remove their copies, and will do that.
> After a while they will report to the name node that the copies have been
> actually deleted.
> Until they report the name node assumes the copies still exist.
> Now the client decides to increase replication back to 3 BEFORE the data nodes
> reported the copies are deleted. Then the name node can choose one of the
> data nodes,
> which it thinks have a block copy, to replicate the block to new data nodes.
> This setting is quite unusual but possible even without variable replications.
> 5) Logging for name and data nodes is improved in several cases.
> E.g. data nodes never logged that they deleted a block.
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