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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3579) Support property groups in Hadoop configuration
Date Wed, 18 Jun 2008 17:06:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3579?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12606011#action_12606011
] 

Steve Loughran commented on HADOOP-3579:
----------------------------------------

First, I do work on Configuration Management, so I have clear goal of plugging in my own back
end to the hadoop config system. I have that already, I just want to do it more cleanly. And
yes, we are hierarchical because it scales well.  

One thing to consider here is the option of arbitrary nesting, so a group can have a subgroup

<group name="queues">
 <group name="queue1" >
  <property><name>timeout<name><value>30000</value></property>
 </group>
 <group name="queue2" >
  <property><name>timeout<name><value>30000</value></property>
  <group name="users" >
   <property><name>user1<name><value>stevel</value></property>
   <property><name>user2<name><value>julio</value></property>
  </group>
 </group>
<group>

You get the idea. Now, this immediately blurs with arrays. What is the difference between
a one-level array of values and a child group? not much.

In SmartFrog we have both cross referencing and inheritance; in XML form that would be something
like:
<group name="queue2" extends="queue1" >

This is the kind of thing that different back ends should be allowed to do, but it doesnt
have to be pushed into the standard XML format, as for a wire representation (which the XML
format is), you can have all this preresolved. 

We can give a presentation on what we have if people are interested; something online with
demos of working code -a precursor of what we'll show in the UK user group meet



> Support property groups in Hadoop configuration
> -----------------------------------------------
>
>                 Key: HADOOP-3579
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3579
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: conf
>            Reporter: Hemanth Yamijala
>
> Hadoop configuration is currently a list of key and value pairs. There are some use-cases
to support configuring groups of related properties. There could also be multiple instances
of such groups. The issue is for adding support for such configuration.

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