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From "Hemanth Yamijala (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3479) Implement configuration items useful for Hadoop resource manager (v1)
Date Wed, 02 Jul 2008 15:51:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3479?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12609958#action_12609958
] 

Hemanth Yamijala commented on HADOOP-3479:
------------------------------------------

It appears we need the overlay feature, after all. A failed test case in TestConfiguration
when I made the change highlighted its use. 

Consider the following sequence of operations:

{code}
conf.addResource(someResource);
conf.set("somekey", "somevalue");
conf.addResource(someOtherResource);
{code}

At step 3, the properties object is cleared. If the overlay is not present, then it basically
means that the value of "somekey" is lost at this point. The presence of the overlay makes
the set values to come back when the resources are reloaded. Also, the reason it is called
overlay seems to be because the values set via the setter methods override everything else.
This is because they are added at the last step in the getProps method.

Thinking about this, it seemed to make sense to retain this behavior in reloadConfiguration,
as in some way it is identical to addResource of all resources again in order.

So, in summary, the changes I made based on Doug's comments are:
- Modified the behavior of reloadConfiguration to not clear the overlaid properties
- Enhanced the test case of reload to make sure the overlay behavior is retained. This makes
the testcase similar to the testOverlay method in TestConfiguration, which, very usefully,
highlighted the need for the overlay feature.
- Calling reloadConfiguration from addResource
- Removed the first parameter of addResource, and since now the names would clash, renamed
that method to addResourceObject.

> Implement configuration items useful for Hadoop resource manager (v1)
> ---------------------------------------------------------------------
>
>                 Key: HADOOP-3479
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3479
>             Project: Hadoop Core
>          Issue Type: New Feature
>            Reporter: Hemanth Yamijala
>            Assignee: Hemanth Yamijala
>         Attachments: 3479.1.patch, 3479.2.patch, 3479.3.patch, 3479.patch
>
>
> HADOOP-3421 lists requirements for a new resource manager for Hadoop. Implementation
for these will require support for new configuration items in Hadoop. This JIRA is to define
such configuration, and track it's implementation.

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