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From "Todd Lipcon (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, 14 Jan 2010 05:12:54 GMT

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

Todd Lipcon updated HDFS-630:
-----------------------------

    Attachment: hdfs-630-0.20.txt

Here's a patch against branch-0.20 that we are evaluating for inclusion in our distro, in
case anyone else is interested in applying it on their own. This is a new feature and the
patch contains a fair amount of hackery, so I don't intend this to be committed to Apache's
branch-0.20.

> 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: Improvement
>          Components: hdfs client, name-node
>    Affects Versions: 0.21.0
>            Reporter: Ruyue Ma
>            Assignee: Cosmin Lehene
>         Attachments: 0001-Fix-HDFS-630-0.21-svn-1.patch, 0001-Fix-HDFS-630-0.21-svn.patch,
0001-Fix-HDFS-630-for-0.21-and-trunk-unified.patch, 0001-Fix-HDFS-630-for-0.21.patch, 0001-Fix-HDFS-630-svn.patch,
0001-Fix-HDFS-630-svn.patch, 0001-Fix-HDFS-630-trunk-svn-1.patch, 0001-Fix-HDFS-630-trunk-svn-2.patch,
0001-Fix-HDFS-630-trunk-svn-3.patch, 0001-Fix-HDFS-630-trunk-svn-3.patch, hdfs-630-0.20.txt,
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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