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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2576) Namenode should have a favored nodes hint to enable clients to have control over block placement.
Date Thu, 25 Apr 2013 20:44:16 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2576?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13642189#comment-13642189

Tsz Wo (Nicholas), SZE commented on HDFS-2576:

- In BlockPlacementPolicyDefault, it should use the oldExcludedNodes when choosing the remaining
nodes.  Also, what should happen if a node is in both favoredNodes and excludedNodes?

- In BlockPlacementPolicy and BlockPlacementPolicyDefault, use Collections.<DatanodeDescriptor>emptyList()
instead of new ArrayList<DatanodeDescriptor>().

- Change void resolveNetworkLocation(DatanodeDescriptor) to String resolveNetworkLocation(DatanodeID).
 Then, we only need to create DatanodeID but not DatanodeDescriptor in the new resolveNetworkLocation(String)

- Move getDatanodeDescriptor(String address) from BlockManager to DatanodeManager.
> Namenode should have a favored nodes hint to enable clients to have control over block
> -------------------------------------------------------------------------------------------------
>                 Key: HDFS-2576
>                 URL: https://issues.apache.org/jira/browse/HDFS-2576
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>            Reporter: Pritam Damania
>            Assignee: Devaraj Das
>             Fix For: 2.0.5-beta
>         Attachments: hdfs-2576-1.txt, hdfs-2576-trunk-1.patch, hdfs-2576-trunk-2.patch,
hdfs-2576-trunk-7.1.patch, hdfs-2576-trunk-7.patch, hdfs-2576-trunk-8.1.patch, hdfs-2576-trunk-8.patch
> Sometimes Clients like HBase are required to dynamically compute the datanodes it wishes
to place the blocks for a file for higher level of locality. For this purpose there is a need
of a way to give the Namenode a hint in terms of a favoredNodes parameter about the locations
where the client wants to put each block. The proposed solution is a favored nodes parameter
in the addBlock() method and in the create() file method to enable the clients to give the
hints to the NameNode about the locations of each replica of the block. Note that this would
be just a hint and finally the NameNode would look at disk usage, datanode load etc. and decide
whether it can respect the hints or not.

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