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Date: Wed, 30 Sep 2009 09:17:23 -0700 (PDT)
From: "Cosmin Lehene (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Subject: [jira] Updated: (HDFS-630) In
 DFSOutputStream.nextBlockOutputStream(), the client can exclude specific
 datanodes when locating the next block.
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     [ https://issues.apache.org/jira/browse/HDFS-630?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

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

    Attachment: HDFS-630.patch

Patch for 0.20 branch. 

Added 
public LocatedBlock addBlock(String src, String clientName, DatanodeInfo[] excludedNodes) throws IOException;

to ClientProtocol and implemented methods in both DFSClient and NameNode

Added method to FSNameSystem too 

DFSClient will 
keep track of nodes that timeout when creating a new block and pass that list when retrying.  

NameNode will pass the excludedNodes list to FSNameSystem and so on. 

Fixed /src/test/org/apache/hadoop/hdfs/TestDFSClientRetries.java to reflect changes in DFSClient

Kept the old interface as well on server side. 

We've tested on a cluster with HBase on top and it worked fine. 

> 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: 0.20.1, 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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