JRuby on Hadoop¶ ↑

JRuby on Hadoop is a thin wrapper for Hadoop Mapper / Reducer by JRuby. We recommend to use this with hadoop-papyrus on the github / gemcutter.

Required gems are all on GemCutter.

1. Upgrade your rubygem to 1.3.5

2. Install gems

$ gem install jruby-on-hadoop

1. Run Hadoop cluster on your machines and set HADOOP_HOME env variable.

2. put files into your hdfs. ex) test/inputs/file1

3. Now you can run ‘joh’ like below:

$ joh examples/wordcount.rb test/inputs test/outputs

You can get Hadoop job results in your hdfs test/outputs/part-*

see also examples/wordcount.rb

def setup(conf)
  # setup jobconf
end

def map(key, value, output, reporter)
  # mapper process
  # (wordcount example)
  value.split.each do |word|
    output.collect(word, 1)
  end
end

def reduce(key, values, output, reporter)
  # reducer process
  # (wordcount example)
  sum = 0
  values.each {|v| sum += v }
  output.collect(key, sum)
end

You can build hadoop-ruby.jar by “ant”.

ant

Required to set env HADOOP_HOME for your system. Assumed Hadoop version is 0.19.2.

Koichi Fujikawa <fujibee@gmail.com>

License: Apache License