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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

Running the WordCount program in a distributed cluster environment

This recipe describes how to run a MapReduce computation in a distributed Hadoop v2 cluster.

Getting ready

Start the Hadoop cluster by following the Setting up HDFS recipe or the Setting up Hadoop ecosystem in a distributed cluster environment using a Hadoop distribution recipe.

How to do it...

Now let's run the WordCount sample in the distributed Hadoop v2 setup:

  1. Upload the wc-input directory in the source repository to the HDFS filesystem. Alternatively, you can upload any other set of text documents as well.
    $ hdfs dfs -copyFromLocal wc-input .
    
  2. Execute the WordCount example from the HADOOP_HOME directory:
    $ hadoop jar hcb-c1-samples.jar \
    chapter1.WordCount \
    wc-input wc-output
    
  3. Run the following commands to list the output directory and then look at the results:
    $hdfs dfs -ls wc-output
    Found 3 items
    -rw-r--r--   1 joesupergroup0 2013-11-09 09:04 /data/output1/_SUCCESS
    drwxr-xr-x   - joesupergroup0 2013-11-09 09:04 /data/output1/_logs
    -rw-r--r--   1 joesupergroup1306 2013-11-09 09:04 /data/output1/part-r-00000
    
    $ hdfs dfs -cat wc-output/part*
    

How it works...

When we submit a job, YARN would schedule a MapReduce ApplicationMaster to coordinate and execute the computation. ApplicationMaster requests the necessary resources from the ResourceManager and executes the MapReduce computation using the containers it received from the resource request.

There's more...

You can also see the results of the WordCount application through the HDFS monitoring UI by visiting http://NAMANODE:50070.

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