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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-785) Divide the server and client configurations
Date Mon, 30 Apr 2007 22:48:15 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-785?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12492807
] 

Doug Cutting commented on HADOOP-785:
-------------------------------------

> I think it's also important not to try to overprotect users [ ... ]

I agree.  Especially when doing so adds code that will need to be maintained.  I think marking
things that should not normally be used as "Expert" should be sufficient.  The biggest problem
with dangerous knobs in my experience is that they generate spurious bug reports from folks
who don't understand what they're really for and abuse them.  I think this is primarily a
documentation problem.  We should advise reasonable values, and folks who ignore that and
provide ridiculous values deserve ridiculous behavior.


> 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
>         Assigned To: Milind Bhandarkar
>
> 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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