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 – killing the NameNode process


Let's now kill the NameNode process, which we should expect to directly stop us from accessing HDFS and by extension, prevent the MapReduce jobs from executing:

Note

Don't try this on an operationally important cluster. Though the impact will be short-lived, it effectively kills the entire cluster for a period of time.

  1. Log onto the NameNode host and list the running processes:

    $ jps
    2372 SecondaryNameNode
    2118 NameNode
    2434 JobTracker
    5153 Jps
    
  2. Kill the NameNode process. Don't worry about SecondaryNameNode, it can keep running.

  3. Try to access the HDFS filesystem:

    $ hadoop fs -ls /
    11/12/13 16:00:05 INFO ipc.Client: Retrying connect to server: /10.0.0.100:9000. Already tried 0 time(s).
    11/12/13 16:00:06 INFO ipc.Client: Retrying connect to server: /10.0.0.100:9000. Already tried 1 time(s).
    11/12/13 16:00:07 INFO ipc.Client: Retrying connect to server: /10.0.0.100:9000. Already tried 2 time(s).
    11/12/13 16:00:08 INFO ipc.Client: Retrying connect to...