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https://issues.apache.org/jira/browse/HADOOP-6105?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12727615#action_12727615
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Philip Zeyliger commented on HADOOP-6105:
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Hemanth,
This JIRA is about backwards-compatibility of deprecated keys, which is
something my comment addresses, so I thought it fit in well here. Think of it
as an alternative solution to the problem you're trying to solve by keeping the
map of deprecated keys in Configuration.java. Keeping a deprecation map is
expedient and simple, but I think it may hamper a better, longer-term solution.
The design goals above are "out of thin air" (in the sense that they haven't
been discussed on JIRA outside of the JIRAs mentioned above and MAPREDUCE-475),
though I hope they're reasonable. They were discussed a bit at
http://wiki.apache.org/hadoop/DeveloperOffsite20090612, too. That said, I hope
they help to frame the conversation a bit
I very very much want there to be a path to be able to rename configuration
keys, but I want to make sure that the solution that comes out of this JIRA is
compatible with some future work.
-- 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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