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From "Arun C Murthy (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-785) Divide the server and client configurations
Date Thu, 06 Sep 2007 06:36:32 GMT

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

Arun C Murthy updated HADOOP-785:

    Status: Open  (was: Patch Available)

Ok, looks like we have a reasonable consensus... +1.

W.r.t add{Default|Final}Resources it's a little tricky... clearly we'll deprecate them for
now and here is the interim plan:
a) Keep the 2 separate default/final lists
b) Load default resources first (front-to-back as is)
c) Load final resources next (front-to-back, not back-to-front as today)
d) Remove all this code in the next release and have a single list of resouces thus doing
away with the notion of default/final resources. I'll file a follow-on jira for this task.

Clearly, process parameters marked as 'force' from all configs, but once a param is marked
as 'force' then subsequent ones from other configs will not be parsed. Thus a 'force' config-param
fron hadoop-default.xml essentially is a 'constant'.

> 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
> 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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