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From "Alejandro Abdelnur (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-5946) Webhdfs DN choosing code is flawed
Date Thu, 13 Feb 2014 19:41:23 GMT

    [ https://issues.apache.org/jira/browse/HDFS-5946?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13900645#comment-13900645

Alejandro Abdelnur commented on HDFS-5946:

How about the following to provide some level of load balancing we should get the DNs of the
first block, filter out decommissioned ones and choose randomly among the avail ones. 

> Webhdfs DN choosing code is flawed
> ----------------------------------
>                 Key: HDFS-5946
>                 URL: https://issues.apache.org/jira/browse/HDFS-5946
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode, webhdfs
>    Affects Versions: 3.0.0, 2.4.0
>            Reporter: Daryn Sharp
>            Priority: Critical
> HDFS-5891 improved the performance of redirecting webhdfs clients to a DN.  Instead of
attempting a connection with a 1-minute timeout, the NN skips decommissioned nodes.
> The logic appears flawed.  It finds the index of the first decommissioned node, if any,
> * Throws an exception if index = 0, even if other nodes later in the list are not decommissioned.
> * Else picks a random node prior to the index.  Let's say there are 10 replicas, 2nd
location is decommissioned.  All clients will be redirected to the first location even though
there are 8 other valid locations.

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