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From "Allen Wittenauer (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-785) Divide the server and client configurations
Date Tue, 21 Aug 2007 20:36:31 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-785?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12521577
] 

Allen Wittenauer commented on HADOOP-785:
-----------------------------------------

I'll openly admit that I'm still processing the contents of this thread, but that isn't going
to stop me from throwing this into the ring:

If I think about a heterogeneous cluster, the thought of having to have multiple copies of
the same config file/directories with just slight differences because one machine is a dual
core opteron and this other one over here is a 32-thread capable ultrasparc t1 doesn't really
fill me with glee.  I see significant admin headaches keeping track of which values need to
get modified for what architectures.

Also:

I think it is fair to say that in our experiences, most of our configuration headaches actually
come from hadoop-env.sh. I realize that doesn't appear to be the topic du jour, but... I'm
just sayin'.... 


> 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
>
>
> 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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