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Hadoop MapReduce v2 Cookbook - Second Edition: RAW

Hadoop MapReduce v2 Cookbook - Second Edition: RAW - Second Edition

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Hadoop MapReduce v2 Cookbook - Second Edition: RAW

Hadoop MapReduce v2 Cookbook - Second Edition: RAW

4.4 (7)

Overview of this book

If you are a Big Data enthusiast and wish to use Hadoop v2 to solve your problems, then this book is for you. This book is for Java programmers with little to moderate knowledge of Hadoop MapReduce. This is also a one-stop reference for developers and system admins who want to quickly get up to speed with using Hadoop v2. It would be helpful to have a basic knowledge of software development using Java and a basic working knowledge of Linux.
Table of Contents (12 chapters)
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11
Index

Implementing a custom Hadoop key type


The instances of Hadoop MapReduce key types should have the ability to compare against each other for sorting purposes. In order to be used as a key type in a MapReduce computation, a Hadoop Writable data type should implement the org.apache.hadoop.io.WritableComparable<T> interface. The WritableComparable interface extends the org.apache.hadoop.io.Writable interface and adds the compareTo() method to perform the comparisons.

In this recipe, we modify the LogWritable data type of the Implementing a custom Hadoop Writable data type recipe to implement the WritableComparable interface.

How to do it...

The following are the steps to implement a custom Hadoop WritableComparable data type for the HTTP server log entries, which uses the request hostname and timestamp for comparison.

  1. Modify the LogWritable class to implement the org.apache.hadoop.io.WritableComparable interface:

    public class LogWritable implements
      WritableComparable<LogWritable> {...
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Hadoop MapReduce v2 Cookbook - Second Edition: RAW
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