Run your Mapreduce programme in standlone Mode and PseudoDistributed mode

 

  hadoop.tmp.dir
  /app/hadoop/tmp
  A base for other temporary directories.


  fs.default.name
  hdfs://hostname:9000
  The name of the default file system. A URI whose
  scheme and authority determine the FileSystem implementation.
  

mapred.job.tracker
    hostname:8021

 package org.apache.hadoop.examples;
import java.io.IOException;
import java.util.StringTokenizer;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;

public class WordCount {

public static class TokenizerMapper 
   extends Mapper{

private final static IntWritable one = new IntWritable(1);
private Text word = new Text();

public void map(Object key, Text value, Context context
                ) throws IOException, InterruptedException {
  StringTokenizer itr = new StringTokenizer(value.toString());
  while (itr.hasMoreTokens()) {
    word.set(itr.nextToken());
    context.write(word, one);
    }
  }
}

public static class IntSumReducer 
   extends Reducer {
private IntWritable result = new IntWritable();

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

public static void main(String[] args) throws Exception {
Configuration conf = new Configuration();

// Add below lines , to create pseudo distributed mode

Job job = new Job(conf, "word count");
job.setJarByClass(WordCount.class);
job.setMapperClass(TokenizerMapper.class);
job.setCombinerClass(IntSumReducer.class);
job.setReducerClass(IntSumReducer.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
FileInputFormat.addInputPath(job, new Path(“/home/user/input/”));
FileOutputFormat.setOutputPath(job, new Path(“/home/user/output/”));
System.exit(job.waitForCompletion(true) ? 0 : 1);
}
}
 

 conf.set("fs.default.name","hdfs://hostname:9000");
    conf.set("mapred.job.tracker","hostname:8021");