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From "Owen O'Malley (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-785) Divide the server and client configurations
Date Fri, 17 Aug 2007 20:24:31 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-785?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12520658
] 

Owen O'Malley commented on HADOOP-785:
--------------------------------------

I'm pretty confused about why you want a second file that contains a list of attribute names.

It absolutely can not be a list of attribute name/value pairs, because that would put us back
in the current mess of two places to set things.

Having a single attribute that just lists the attribute names that need to be set will be
simple and direct. It is very unlikely to be misconfigured. Furthermore, it is addressing
the user delegation/switching that is pretty unique to map/reduce and other batch systems.
I can't imagine what Nutch or  Hbase would want to add to the list.

> 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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