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https://issues.apache.org/jira/browse/MAPREDUCE-954?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12757128#action_12757128
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Tom White commented on MAPREDUCE-954:
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Thanks for the new patch, Arun. Can we mark the interfaces as "Public
Evolving"? This would overcome the problems with API evolvability.
Some other feedback:
* I'm not sure that WrappedMapper and WrappedReducer belong in a "lib" package,
since the classes in "lib" are user-facing, and these are framework classes.
(People might see them and wonder how they can use a WrappedMapper in their
application, for example.) They would be better in the task package I think.
* Can we move org.apache.hadoop.mapreduce.task to
org.apache.hadoop.mapreduce.server.task to better emphasise that this is
non-user code. This reflects the packaging of HDFS more, where things that run
on the cluster are under a "server" package. We should have another JIRA to
move org.apache.hadoop.mapreduce.task.reduce to
org.apache.hadoop.mapreduce.server.task.reduce.
* It's a shame JobContextImpl is public and in org.apache.hadoop.mapreduce
since users shouldn't be exposed to it. Can we move it to another package?
* Since Job extends JobContextImpl you don't need the changes that change the
{{\*_ATTR}} constants (e.g. {{OUTPUT_FORMAT_CLASS_ATTR}}) to
{{JobContextImpl.\*_ATTR}} - they can be referred to directly.
* What's the compatibility story for previous releases? Would a 0.20 MR program
written to the new ("mapreduce" package) API work with the new interfaces
unchanged? What about a 0.20 program using the old MR API - will it continue to
work with the old MR API with these changes?
> The new interface's Context objects should be interfaces
> --------------------------------------------------------
>
> Key: MAPREDUCE-954
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-954
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: client
> Reporter: Owen O'Malley
> Assignee: Arun C Murthy
> Fix For: 0.21.0
>
> Attachments: MAPREDUCE-954.patch, MAPREDUCE-954.patch,
> MAPREDUCE-954.patch, MAPREDUCE-954.patch, MAPREDUCE-954.patch
>
>
> When I was doing HADOOP-1230, I was persuaded to make the Context objects as
> classes. I think that was a serious mistake. It caused a lot of information
> leakage into the public classes.
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