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Hadoop Beginner's Guide

Hadoop Beginner's Guide

3.7 (13)
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Hadoop Beginner's Guide

Hadoop Beginner's Guide

3.7 (13)
Buy this Book

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)
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Hadoop Beginner's Guide
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Hadoop Beginner's Guide
Credits
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Credits
About the Author
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About the Author
About the Reviewers
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About the Reviewers
www.PacktPub.com
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www.PacktPub.com
Preface
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Preface
Free Chapter
1
What It's All About
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What It's All About
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Big data processing
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Cloud computing with Amazon Web Services
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Summary
2
Getting Hadoop Up and Running
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Getting Hadoop Up and Running
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Hadoop on a local Ubuntu host
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Time for action – checking the prerequisites
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Time for action – downloading Hadoop
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Time for action – setting up SSH
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Time for action – using Hadoop to calculate Pi
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Time for action – configuring the pseudo-distributed mode
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Time for action – changing the base HDFS directory
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Time for action – formatting the NameNode
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Time for action – starting Hadoop
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Time for action – using HDFS
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Time for action – WordCount, the Hello World of MapReduce
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Using Elastic MapReduce
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Time for action – WordCount on EMR using the management console
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Comparison of local versus EMR Hadoop
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Summary
3
Understanding MapReduce
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Understanding MapReduce
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Key/value pairs
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The Hadoop Java API for MapReduce
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Writing MapReduce programs
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Time for action – setting up the classpath
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Time for action – implementing WordCount
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Time for action – building a JAR file
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Time for action – running WordCount on a local Hadoop cluster
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Time for action – running WordCount on EMR
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Time for action – WordCount the easy way
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Walking through a run of WordCount
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Time for action – WordCount with a combiner
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Time for action – fixing WordCount to work with a combiner
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Hadoop-specific data types
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Time for action – using the Writable wrapper classes
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Input/output
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Summary
4
Developing MapReduce Programs
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Developing MapReduce Programs
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Using languages other than Java with Hadoop
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Time for action – implementing WordCount using Streaming
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Analyzing a large dataset
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Time for action – summarizing the UFO data
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Time for action – summarizing the shape data
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Time for action – correlating of sighting duration to UFO shape
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Time for action – performing the shape/time analysis from the command line
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Time for action – using ChainMapper for field validation/analysis
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Time for action – using the Distributed Cache to improve location output
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Counters, status, and other output
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Time for action – creating counters, task states, and writing log output
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Summary
5
Advanced MapReduce Techniques
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Advanced MapReduce Techniques
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Simple, advanced, and in-between
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Joins
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Time for action – reduce-side join using MultipleInputs
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Graph algorithms
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Time for action – representing the graph
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Time for action – creating the source code
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Time for action – the first run
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Time for action – the second run
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Time for action – the third run
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Time for action – the fourth and last run
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Using language-independent data structures
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Time for action – getting and installing Avro
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Time for action – defining the schema
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Time for action – creating the source Avro data with Ruby
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Time for action – consuming the Avro data with Java
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Time for action – generating shape summaries in MapReduce
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Time for action – examining the output data with Ruby
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Time for action – examining the output data with Java
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Summary
6
When Things Break
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When Things Break
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Failure
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Time for action – killing a DataNode process
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Time for action – the replication factor in action
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Time for action – intentionally causing missing blocks
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Time for action – killing a TaskTracker process
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Time for action – killing the JobTracker
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Time for action – killing the NameNode process
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Time for action – causing task failure
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Time for action – handling dirty data by using skip mode
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Summary
7
Keeping Things Running
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Keeping Things Running
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A note on EMR
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Hadoop configuration properties
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Time for action – browsing default properties
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Setting up a cluster
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Time for action – examining the default rack configuration
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Time for action – adding a rack awareness script
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Cluster access control
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Time for action – demonstrating the default security
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Managing the NameNode
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Time for action – adding an additional fsimage location
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Time for action – swapping to a new NameNode host
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Managing HDFS
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MapReduce management
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Time for action – changing job priorities and killing a job
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Scaling
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Summary
8
A Relational View on Data with Hive
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A Relational View on Data with Hive
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Overview of Hive
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Setting up Hive
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Time for action – installing Hive
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Using Hive
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Time for action – creating a table for the UFO data
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Time for action – inserting the UFO data
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Time for action – validating the table
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Time for action – redefining the table with the correct column separator
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Time for action – creating a table from an existing file
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Time for action – performing a join
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Time for action – using views
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Time for action – exporting query output
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Time for action – making a partitioned UFO sighting table
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Time for action – adding a new User Defined Function (UDF)
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Hive on Amazon Web Services
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Time for action – running UFO analysis on EMR
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Summary
9
Working with Relational Databases
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Working with Relational Databases
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Common data paths
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Setting up MySQL
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Time for action – installing and setting up MySQL
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Time for action – configuring MySQL to allow remote connections
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Time for action – setting up the employee database
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Getting data into Hadoop
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Time for action – downloading and configuring Sqoop
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Time for action – exporting data from MySQL to HDFS
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Time for action – exporting data from MySQL into Hive
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Time for action – a more selective import
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Time for action – using a type mapping
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Time for action – importing data from a raw query
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Getting data out of Hadoop
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Time for action – importing data from Hadoop into MySQL
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Time for action – importing Hive data into MySQL
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Time for action – fixing the mapping and re-running the export
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AWS considerations
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Summary
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Data Collection with Flume
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Data Collection with Flume
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A note about AWS
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Data data everywhere...
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Time for action – getting web server data into Hadoop
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Introducing Apache Flume
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Time for action – installing and configuring Flume
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Time for action – capturing network traffic in a log file
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Time for action – logging to the console
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Time for action – capturing the output of a command to a flat file
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Time for action – capturing a remote file in a local flat file
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Time for action – writing network traffic onto HDFS
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Time for action – adding timestamps
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Time for action – multi level Flume networks
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Time for action – writing to multiple sinks
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The bigger picture
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Summary
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Where to Go Next
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Where to Go Next
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What we did and didn't cover in this book
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Upcoming Hadoop changes
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Alternative distributions
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Other Apache projects
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Other programming abstractions
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AWS resources
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Sources of information
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Summary
Pop Quiz Answers
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Pop Quiz Answers
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Chapter 3, Understanding MapReduce
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Chapter 7, Keeping Things Running
Index
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Index

Time for action – fixing WordCount to work with a combiner

Let's make the necessary modifications to WordCount to correctly use a combiner.

Copy WordCount2.java to a new file called WordCount3.java and change the reduce method as follows:

public void reduce(Text key, Iterable<IntWritable> values,            
Context context) throws IOException, InterruptedException 
{
int total = 0 ;
for (IntWritable val : values))
{
total+= val.get() ;
}
            context.write(key, new IntWritable(total));
}

Remember to also change the class name to WordCount3 and then compile, create the JAR file, and run the job as before.

What just happened?

The output is now as expected. Any map-side invocations of the combiner performs successfully and the reducer correctly produces the overall output value.

Tip

Would this have worked if the original reducer was used as the combiner and the new reduce implementation as the reducer? The answer is no, though our test example would not have demonstrated it. Because...

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