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Date: Tue, 11 Sep 2007 07:40:33 -0700 (PDT)
From: "Arun C Murthy (JIRA)" <jira@apache.org>
To: hadoop-dev@lucene.apache.org
Subject: [jira] Commented: (HADOOP-785) Divide the server and client
 configurations
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    [ https://issues.apache.org/jira/browse/HADOOP-785?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12526470 ] 

Arun C Murthy commented on HADOOP-785:
--------------------------------------

Thanks for the new patch Doug! I definitely planned on on fixing documentation etc. (e.g. http://wiki.apache.org/lucene-hadoop/HowToConfigure) but appreciate your help! *smile*


> Divide the server and client configurations
> -------------------------------------------
>
>                 Key: HADOOP-785
>                 URL: https://issues.apache.org/jira/browse/HADOOP-785
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: conf
>    Affects Versions: 0.9.0
>            Reporter: Owen O'Malley
>            Assignee: Arun C Murthy
>             Fix For: 0.15.0
>
>         Attachments: HADOOP-785_1_20070903.patch, HADOOP-785_2_20070906.patch, HADOOP-785_3_20070908.patch, HADOOP-785_4.patch
>
>
> The configuration system is easy to misconfigure and I think we need to strongly divide the server from client configs. 
> An example of the problem was a configuration where the task tracker has a hadoop-site.xml that set mapred.reduce.tasks to 1. Therefore, the job tracker had the right number of reduces, but the map task thought there was a single reduce. This lead to a hard to find diagnose failure.
> Therefore, I propose separating out the configuration types as:
> class Configuration;
> // reads site-default.xml, hadoop-default.xml
> class ServerConf extends Configuration;
> // reads hadoop-server.xml, $super
> class DfsServerConf extends ServerConf;
> // reads dfs-server.xml, $super
> class MapRedServerConf extends ServerConf;
> // reads mapred-server.xml, $super
> class ClientConf extends Configuration;
> // reads hadoop-client.xml, $super
> class JobConf extends ClientConf;
> // reads job.xml, $super
> Note in particular, that nothing corresponds to hadoop-site.xml, which overrides both client and server configs. Furthermore, the properties from the *-default.xml files should never be saved into the job.xml.

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