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From "Konstantin Boudnik (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-630) In DFSOutputStream.nextBlockOutputStream(), the client can exclude specific datanodes when locating the next block.
Date Tue, 24 Nov 2009 18:22:39 GMT

    [ https://issues.apache.org/jira/browse/HDFS-630?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12782068#action_12782068
] 

Konstantin Boudnik commented on HDFS-630:
-----------------------------------------

I have missed this JIRA in the doing, but am going to comment on anyway. The comment is about
the newly added test which is developed for JUnit v.3
{noformat}
+public class TestDFSClientExcludedNodes extends TestCase {
{noformat}
I'd like to ask all reviewers to pay attention to the fact that new tests are suppose to be
written for JUnit v.4.
Here's a [short instruction|http://wiki.apache.org/hadoop/HowToDevelopUnitTests] on how it
should be done.

Also, the commit message has wrong JIRA number in it. It says HBASE-630 instead of HDFS-630

> 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: Cosmin Lehene
>            Priority: Minor
>         Attachments: 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, 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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