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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-25) a new map/reduce example and moving the examples from src/java to src/examples
Date Tue, 07 Feb 2006 00:02:58 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-25?page=comments#action_12365365 ] 

Doug Cutting commented on HADOOP-25:
------------------------------------

A few comments:

I prefer 'ant compile' to do the minimum required for development, so it shouldn't build examples.
 Similarly, I prefer 'ant jar' to build only the primary jar.  Examples, test code, javadoc,
etc. should be out of the compile-debug loop.

This should probably go in org.apache.hadoop.examples rather than org.apache.hadoop.mapred.demo,
no?

The mapper is missing a javadoc comment.

The usage string in the javadoc should probably instead propose something like: bin/hadoop
org.apache.hadoop.examples.WordCount, and we should make sure that the examples jar goes on
the classpath.

I also wonder whether we should encourage folks to explicitly set the number of map and reduce
tasks for each job.  I prefer to think of this as normally a site configuration and/or automatic
process.

Finally, since I'm already nitpicking, doesn't the 'try' block in your main() do the same
thing as just permitting main() to throw IOException?  The JVM prints a stack trace, no?


> a new map/reduce example and moving the examples from src/java to src/examples
> ------------------------------------------------------------------------------
>
>          Key: HADOOP-25
>          URL: http://issues.apache.org/jira/browse/HADOOP-25
>      Project: Hadoop
>         Type: Improvement
>   Components: mapred
>     Reporter: Owen O'Malley
>     Priority: Minor
>  Attachments: examples.patch
>
> The new example is the word count example from Google's paper. I moved the examples into
a separate jar file to demonstrate how to run stand-alone application code.

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