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https://issues.apache.org/jira/browse/HADOOP-6105?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12731560#action_12731560
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Philip Zeyliger commented on HADOOP-6105:
-----------------------------------------

Owen,

Apologies for missing this e-mail for so long.  I'm behind on the "all-jira" 
bucket, and I failed to set a watch.

Hemanth, you should definitely forge ahead with the simple, expedient solution. 
 

I'd like to convince you and Owen that the more complicated proposal is a net 
win (and I've used a similar system in the past), but I think the best way to 
do that is to actually write the code and transform a few usages.  I've been 
busy with some other deadlines, so when I get there, I'll file a JIRA and 
bother you all again.

(To answer Owen's questions: the couple of classes for ConfigVariable go into 
the configuration package; users are welcome to use the same classes to set 
their variables, or they can set them manually; the documentation for the 
variables themselves is generated, the documentation for the system lives in 
JavaDoc on the individual classes and the package.)

-- Philip



> Provide a way to automatically handle backward compatibility of deprecated 
> keys
> -------------------------------------------------------------------------------
>
>                 Key: HADOOP-6105
>                 URL: https://issues.apache.org/jira/browse/HADOOP-6105
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: conf
>            Reporter: Hemanth Yamijala
>
> There are cases when we have had to deprecate configuration keys. Use cases 
> include, changing the names of variables to better match intent, splitting a 
> single parameter into two - for maps, reduces etc.
> In such cases, we typically provide a backwards compatible option for the old 
> keys. The handling of such cases might typically be common enough to actually 
> add support for it in a generic fashion in the Configuration class. Some 
> initial discussion around this started in HADOOP-5919, but since the project 
> split happened in between we decided to open this issue to fix it in common.

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