Hadoop application cannot find Reducer
I am trying to make a mapreduce application that reads from an Hbase table and writes the job results to a text file. My driver code looks like this:
Configuration conf = HBaseConfiguration.create();
Job job = Job.getInstance (conf, "mr test");
job.setJarByClass(Driverclass.class);
job.setCombinerClass(reducername.class);
job.setReducerClass(reducername.class);
Scan scan = new Scan();
scan.setCaching(500);
scan.setCacheBlocks(false);
String qualifier = "qualifname"; // comma seperated
String family= "familyname";
scan.addColumn(Bytes.toBytes(family), Bytes.toBytes(qualifier));
TableMapReduceUtil.initTableMapperJob("tablename",
scan,
mappername.class,
Text.class, Text.class,
job);
when initTableMapperJob is called I get ClassNotFoundException: class reducecername not found.
The class is defined in another java file in the same package. I used almost the same configuration to try a regular wordcount example and worked great. Then I changed the type of the mapping and the way I set it up and I get this error. Can anyone help me?
Edit: code for the reducer class:
package mr.roadlevelmr;
import java.io.IOException;
import java.util.ArrayList;
import java.util.StringTokenizer;
import org.apache.hadoop.io.*;
import org.apache.hadoop.mapreduce.Reducer;
public class reducername extends Reducer <Text, Text, Text, Text>{
private Text result= new Text();
public void reduce (Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException{
ArrayList<String> means = new ArrayList<String>();
for (Text val : values){
means.add(String.valueOf(val.getBytes()));
}
result.set(newMean(means));
context.write(key, result);
}
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1 answer
you have to use Map reduce utility like below:
TableMapReduceUtil.initTableMapperJob("tablename",
scan,
mappername.class,
Text.class, Text.class,
job);Ok think I found the issue!
than add a reducer and an adder
job.setCombinerClass(reducername.class);
job.setReducerClass(reducername.class);
boolean b = job.waitForCompletion(true);
Instead of adding a reducer to a table mapping job
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