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From "Cosmin Lehene (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HDFS-630) In DFSOutputStream.nextBlockOutputStream(), the client can exclude specific datanodes when locating the next block.
Date Thu, 15 Oct 2009 15:40:31 GMT

     [ https://issues.apache.org/jira/browse/HDFS-630?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Cosmin Lehene updated HDFS-630:
-------------------------------

    Affects Version/s:     (was: 0.20.1)
               Status: Patch Available  (was: Open)

Adapted for 0.21 branch. 

Added excludedNodes back to BlockPlacementPolicy. 
Adapted to use HashMap<Node, Node> instead of List<Node> since BlockPlacementPolicyDefault
was changed to use HashMap. However I'm not sure if it's supposed to be a HashMap... 
Luckily, Dhruba didn't removed the code that dealt with excludedNodes from BlockPlacementPolicyDefault
so I only had to wire up the methods.


I also added a "unit" test - it's practically a functional test that spins up a DFSMiniCluster
with 3 DataNodes and kills one before creating the file. 

> In DFSOutputStream.nextBlockOutputStream(), the client can exclude specific datanodes
when locating the next block.
> -------------------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-630
>                 URL: https://issues.apache.org/jira/browse/HDFS-630
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>          Components: hdfs client
>    Affects Versions: 0.21.0
>            Reporter: Ruyue Ma
>            Assignee: Ruyue Ma
>            Priority: Minor
>             Fix For: 0.21.0
>
>         Attachments: HDFS-630.patch
>
>
> created from hdfs-200.
> If during a write, the dfsclient sees that a block replica location for a newly allocated
block is not-connectable, it re-requests the NN to get a fresh set of replica locations of
the block. It tries this dfs.client.block.write.retries times (default 3), sleeping 6 seconds
between each retry ( see DFSClient.nextBlockOutputStream).
> This setting works well when you have a reasonable size cluster; if u have few datanodes
in the cluster, every retry maybe pick the dead-datanode and the above logic bails out.
> Our solution: when getting block location from namenode, we give nn the excluded datanodes.
The list of dead datanodes is only for one block allocation.

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