** Get up and running in less than 5 minutes **

Tis program demonstrates using Hadoop's Map-Reduce concept in Java. The input is a raw data file listing earthquakes by region, magnitude and other information. The goal is to find the maximum magnitude of earthquake for a given region.

1. Download Hadoop 1.1.1 binary [http://mirror.csclub.uwaterloo.ca/apache/hadoop/common/hadoop-1.1.1/hadoop-1.1.1.tar.gz]
2. Extract it to a folder on your computer [tar xvfz hadoop-1.1.1.tar.gz].
3. Setup the JAVA_HOME environment variable to point to the directory where Java is installed. For my Mac OSX, I did the following: $ export JAVA_HOME=/System/Library/Frameworks/JavaVM.framework/Versions/1.6.0/Home
4. Setup the HADOOP_INSTALL environment variable to point the directory where you extracted hadoop binary in step 2: $ export HADOOP_INSTALL=/Users/umermansoor/Documents/hadoop-1.1.1
5. Edit the PATH environment variable: $ export PATH=$PATH:$HADOOP_INSTALL/bin

1. Clone the project: $ git clone [email protected]:umermansoor/hadoop-java-example.git
2. Setup the HADOOP_CLASSPATH environment variable to tell Hadoop where to find the java classes for the sample: $ export HADOOP_CLASSPATH=target/classes/
3. Change to the project directory: $ cd hadoop-java-example
4. Build the project: $ mvn clean install
5. Run the sample: $ hadoop com.umermansoor.App input/input.csv output Note: the output will go to the output/ folder which Hadoop will create when run.

1. Exception: java.lang.NoClassDefFoundError Cause: You didn't setup the HADOOP_CLASSPATH environment variable. Resolution: Setup the variable: $ export HADOOP_CLASSPATH=target/classes/

2. Exception: org.apache.hadoop.mapred.FileAlreadyExistsException or 'Output directory output already exists'. Cause: Output directory already exists. Hadoop requires that the output directory doesn't exists when run. Resolution: Change the output directory or remove the existing one: $ hadoop com.umermansoor.App input/input.csv output_new -- Change the output directory Note: Hadoop failing if the output folder already exists is a good thing: it ensures that you don't accidentally overwrite your previous output.