Hadoop Beginner's Guide

Time for action – examining the output data with Ruby

Now that we have the output data from the job, let's examine it again using Ruby.

1. Create the following as read.rb:

   require 'rubygems'
   require 'avro'
   
   file = File.open('res.avro', 'rb')
   reader = Avro::IO::DatumReader.new()
   dr = Avro::DataFile::Reader.new(file, reader)
   
   dr.each {|record|  
   print record["shape"]," ",record["count"],"\n"
   }
   dr.close

2. Examine the created result file.

   $ ruby read.rb
   blur 1
   cylinder 1
   diamond 2
   formation 1
   light 3
   saucer 1
   

What just happened?

As before, we'll not analyze the Ruby Avro API. The example created a Ruby script that opens an Avro datafile, iterates through each datum, and displays it based on explicitly named fields. Note that the script does not have access to ...