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From Harsh J <qwertyman...@gmail.com>
Subject Re: Printing Debug Messages and Setting up Mapper Classes Programmatically
Date Wed, 09 Feb 2011 03:00:23 GMT

On Wed, Feb 9, 2011 at 6:33 AM, Adam Pridgen
<adam.pridgen@thecoverofnight.com> wrote:
> Hello,
> I am trying to setup my Mapper class before it is set-up to run as a
> task.  Specifically, I am trying to override the method
> Mapper.setup(Mapper.Context).  When I run the MapReduce program I am
> expecting an output to stdout of about about 6 lines along with the
> configuration information read out of the Context.  I have two
> questions:
> --- Am I correctly setting up the mapper set task?

Yes, @Overriding the setup method is the right way to do this with the
new Mapper API.

> --- Do I need to print/debug messages through an API of some sort, or
> is printing output to stdout OK?

While stdout is okay to use, and the outputs of that do get stored in
stdout/stderr files of the Task on the TaskTracker machine, it makes
more sense to use a logger API instead for debugging purposes for
automatic time-stamps, levels of severity, classnames, etc.. Much more
easier to replay logger outputs in mind than stdouts while debugging.

Hadoop comes with commons-logging and log4j libraries for use out-of-the-box.

Harsh J

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