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https://issues.apache.org/jira/browse/HADOOP-785?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12517938
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Enis Soztutar commented on HADOOP-785:
--------------------------------------
BTW, a related issue about configuration parameters is that the names of the
parameters are used in different contexts(in hadoop-*.xml files and in the
code), sometimes resulting in misspelling and confusion. How about the
following *slightly ugly* way to programaticaly access parameter names.
{code}
public class ParameterNames {
private static final int prefixLength
= ParameterNames.class.getCanonicalName().length() + 1;
public static final class fs {
public static final class trash {
public static final class root { }
public static final class interval { }
}
public static final class file {
public static final class impl { }
}
}
public static String getName(Class<?> clazz) {
return clazz.getCanonicalName().substring(prefixLength);
}
}
{code}
and the code to use the name would be :
{code}
String trashPath =
conf.get(ParameterNames.getName(ParameterNames.fs.trash.root.class))
{code}
> 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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