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https://issues.apache.org/jira/browse/MAPREDUCE-954?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12757525#action_12757525
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Arun C Murthy commented on MAPREDUCE-954:
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bq. 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.
Owen & I went back forth on this - finally Owen convinced me it's better to put
it lib.
bq. 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.
We already have the new shuffle in org.apache.hadoop.mapreduce.task.reduce,
thus org.apache.hadoop.mapreduce.task seemed logical.
bq. 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?
Done.
bq. 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.
Done.
* 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?
Yes to both.
> 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,
> 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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