Book Image

Hadoop Beginner's Guide

Book Image

Hadoop Beginner's Guide

Overview of this book

Data is arriving faster than you can process it and the overall volumes keep growing at a rate that keeps you awake at night. Hadoop can help you tame the data beast. Effective use of Hadoop however requires a mixture of programming, design, and system administration skills."Hadoop Beginner's Guide" removes the mystery from Hadoop, presenting Hadoop and related technologies with a focus on building working systems and getting the job done, using cloud services to do so when it makes sense. From basic concepts and initial setup through developing applications and keeping the system running as the data grows, the book gives the understanding needed to effectively use Hadoop to solve real world problems.Starting with the basics of installing and configuring Hadoop, the book explains how to develop applications, maintain the system, and how to use additional products to integrate with other systems.While learning different ways to develop applications to run on Hadoop the book also covers tools such as Hive, Sqoop, and Flume that show how Hadoop can be integrated with relational databases and log collection.In addition to examples on Hadoop clusters on Ubuntu uses of cloud services such as Amazon, EC2 and Elastic MapReduce are covered.
Table of Contents (19 chapters)
Hadoop Beginner's Guide
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

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 the schema for the datafile; the information in the header provides enough data to allow each field to be retrieved.