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From "Michael Bieniosek (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-785) Divide the server and client configurations
Date Mon, 30 Apr 2007 22:27:16 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-785?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12492802
] 

Michael Bieniosek commented on HADOOP-785:
------------------------------------------

> I'd also like to see a set of hard rules for config parameter (whereever they make sense)which
override all parameters so as to ensure a reasonably consistent configuration.

> For e.g. MAX_TASK_FAILURES in HADOOP-1304 - it doesn't make sense to allow a TIP to fail
thousands of times, so even if the user mis-configures it would make sense to check it against
the hard-rule and over-ride the user supplied config value.

I think it's also important not to try to overprotect users -- I don't think people are capriciously
or randomly changing hadoop configuration parameters.  It is frustrating to try to change
a parameter, only to have hadoop ignore me.  In the case where the user submits a truly ridiculous
configuration, perhaps it might be better to error out or print a very loud warning visible
to the job submitter?


> 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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