MapReduce Map Value Mismatch error

Question

Code:

package com.vijaybigdata;


import java.io.IOException;


import org.apache.hadoop.conf.Configuration;

import org.apache.hadoop.fs.Path;

import org.apache.hadoop.io.Text;

import org.apache.hadoop.mapreduce.Job;

import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;

import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;

import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;


public class Driver {

public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {

Configuration conf=new Configuration();

Job job=Job.getInstance(conf);

job.setJarByClass(Driver.class);

job.setMapperClass(MyMapper.class);

job.setReducerClass(MyReducer.class);

job.setOutputKeyClass(Text.class);

job.setOutputValueClass(Text.class);

job.setInputFormatClass(TextInputFormat.class);

job.setOutputFormatClass(TextOutputFormat.class);

FileInputFormat.addInputPath(job, new Path(args[0]));

FileOutputFormat.setOutputPath(job, new Path(args[1]));

System.exit(job.waitForCompletion(true)?0:1);

}


}

Error:

Error:Error: java.io.IOException: Type mismatch in value from map: expected org.apache.hadoop.io.Text, received org.apache.hadoop.io.DoubleWritable
at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.collect(MapTask.java:1084)
at org.apache.hadoop.mapred.MapTask$NewOutputCollector.write(MapTask.java:721)
at org.apache.hadoop.mapreduce.task.TaskInputOutputContextImpl.write(TaskInputOutputContextImpl.java:89)
at org.apache.hadoop.mapreduce.lib.map.WrappedMapper$Context.write(WrappedMapper.java:112)
at com.vijaybigdata.MyMapper.map(MyMapper.java:26)
at com.vijaybigdata.MyMapper.map(MyMapper.java:1)
at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:145)
at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:793)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:341)
at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:164)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:422)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation

Answer 1

Seems like you have not specified few properties in the driver class for MapOutputKey and MapOutputValue. Please add the below properties to your driver class and try the code again.

job.setMapOutputKeyClass(Text.class);

job.setMapOutputValueClass(DoubleWritable.class);