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Posted to mapreduce-dev@hadoop.apache.org by "David Rosenstrauch (JIRA)" <ji...@apache.org> on 2010/08/11 04:45:16 UTC
[jira] Created: (MAPREDUCE-2002) MRUnit driver classes should
provide ability to set a configuration object to be passed into the
mapper/reducer
MRUnit driver classes should provide ability to set a configuration object to be passed into the mapper/reducer
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Key: MAPREDUCE-2002
URL: https://issues.apache.org/jira/browse/MAPREDUCE-2002
Project: Hadoop Map/Reduce
Issue Type: Bug
Components: contrib/mrunit
Affects Versions: 0.20.2
Reporter: David Rosenstrauch
Priority: Minor
Short description:
Enhance the org.apache.hadoop.mrunit.mapreduce.MapDriver, ReduceDriver, and MapReduceDriver unit test driver classes to contain "setConfiguration" and "withConfiguration" methods for passing in user-supplied org.apache.hadoop.conf.Configuration objects, and have those configuration objects eventually get passed on to the Context objects that are passed in to the mapper/reducer "setup" methods. (Rather than passing in an empty Configuration object, as is being done now.)
Long description:
The MRUnit driver classes (i.e., MapDriver, ReduceDriver, and MapReduceDriver) ought to be enhanced to contain methods for setting a Configuration object to be used by the mapper/reducer being tested - i.e., setConfiguration() and withConfiguration().
The only way to effectively pass parameters into a mapper or reducer is by setting properties on a configuration object, which the mapper/reducer can then retrieve in their "setup" step, and use to customize its operation. As a result, specific mappers/reducers may require the presence of specific configuration properties/parameters in order to function correctly (or at all). (I am currently coding such a reducer right now.)
Testing such a mapper/reducer thus requires that the unit testing framework used provide the ability to pass in user-supplied Configuration objects to them so that they can be tested with appropriate parameter values. However, MRUnit currently does not provide this ability. (All mappers/reducers are always passed an empty configuration object.) And there is not even currently any (easy) way for the end-user to fix this problem by creating a simple sub-class that supplies this functionality, as such subclasses would require a substantial reimplementation/override of several MRUnit framework classes.
I believe this something that is not too difficult to fix in the MRUnit framework code, however, and would greatly help the usability of MRUnit.
Although I don't have time to code this enhancement right now, if needed/preferred I could squeeze out some time to code up a patch for this. If that's needed, please let me know.
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