NAME

Hadoop::Streaming::Mapper - Simplify writing Hadoop Streaming jobs. Write a map() and reduce() function and let this role handle the Stream interface.

VERSION

version 0.100060

SYNOPSIS

  #!/usr/bin/env perl
  
  package Wordcount::Mapper;
  use Moose;
  with 'Hadoop::Streaming::Mapper';
  
  sub map {
      my ($self, $key, $value) = @_;
  
      for (split /\s+/, $value) {
          $self->emit( $_ => 1 );
      }
  }
  
  package main;
  Wordcount::Mapper->run;

Your mapper class must implement map($key,$value) and your reducer must implement reduce($key,$value). Your classes will have emit() and run() methods added via role.

METHODS

run

    Package->run();

This method starts the Hadoop::Streaming::Mapper instance.

After creating a new object instance, it reads from STDIN and calls $object->map() on each line of input. Subclasses need only implement map() to produce a complete Hadoop Streaming compatible mapper.

emit

    $object->emit( $key, $value )

This method emits a key,value pair in the format expected by Hadoop::Streaming. It does this by calling $self->put(). This catches errors from put and turns them into warnings.

put

    $object->put( $key, $value )

This method emits a key,value pair to STDOUT in the format expected by Hadoop::Streaming: ( key \t value \n )

AUTHORS

  andrew grangaard <spazm@cpan.org>
  Naoya Ito <naoya@hatena.ne.jp>

COPYRIGHT AND LICENSE

This software is copyright (c) 2010 by Naoya Ito <naoya@hatena.ne.jp>.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.