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From "Arun C Murthy (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-785) Divide the server and client configurations
Date Mon, 20 Aug 2007 20:29:32 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-785?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12521222

Arun C Murthy commented on HADOOP-785:

Here is my final (final final) say on the topic, basically re-stating my preference:

If *I* was maintaining more than one large cluster, I'd prefer to have a separate hadoop-final.xml
where I'd put not only the varying paths, but also some of the hardware specific stuff (e.g.
{{mapred.tasktracker.tasks.maximum}} would depend on how beefy a node is, in a given cluster).


Personally I'd like the convenience of being able to put a small set of hard-limits in different
hadoop-final.xml files (hadoop-final-cluster{1,2,3}.xml), stick them up in subversion/cvs
and being able to quickly glean insights into the various limits. 

IMHO it's harder to do such stuff with a single, large hadoop-site.xml, especially minus the
ability to quickly diff (harder to diff on xml files via cmd-line diff) etc.

Having said that, I'd like to know what *real* admins think of course! *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
> 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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