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

Key/value pairs


Since Chapter 1, What It's All About, we have been talking about operations that process and provide the output in terms of key/value pairs without explaining why. It is time to address that.

What it mean

Firstly, we will clarify just what we mean by key/value pairs by highlighting similar concepts in the Java standard library. The java.util.Map interface is the parent of commonly used classes such as HashMap and (through some library backward reengineering) even the original Hashtable.

For any Java Map object, its contents are a set of mappings from a given key of a specified type to a related value of a potentially different type. A HashMap object could, for example, contain mappings from a person's name (String) to his or her birthday (Date).

In the context of Hadoop, we are referring to data that also comprises keys that relate to associated values. This data is stored in such a way that the various values in the data set can be sorted and rearranged across a set of keys...