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https://issues.apache.org/jira/browse/HADOOP-785?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12520606
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Doug Cutting commented on HADOOP-785:
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bq. My last comment means that we have two config files hadoop-site.xml and
hadoop-site-final.xml. Arun's hadoop-initial and hadoop-final serve the same
purpose i guess.
>From a back-compatibility standpoint it might be simpler to keep the name
>hadoop-site.xml. But, is that name so misleading that we should change it
>anyway? If its semantics are changed (as proposed), to no longer override
>job-specified parameters, then its name may no longer be so misleading, and we
>might not need to use a new name after all. And it would be nice to not force
>folks to rename all their configuration files when they upgrade.
On the other hand, if we change the the semantics of hadoop-site, will that
silently break folks whose configurations depended on the old semantics? That
would argue for new names, so that folks are forced to address the incompatible
change. Thoughts?
> 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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