Java – Unable to access counters in MapReduce’s reducer class

I incremented the counter of the mapper by

public static class TokenizerMapper
extends Mapper<Object, Text, Text, FloatWritable>{  
public static enum MyCounters { TOTAL };  
context.getCounter(MyCounters.TOTAL).increment(1);  

.

I’m trying to get the value of this counter in the reducer class in the following way.

@Override
public void setup(Context context) throws IOException     ,InterruptedException{  
Configuration conf = context.getConfiguration();  
Cluster cluster = new Cluster(conf);  
Job currentJob = cluster.getJob(context.getJobID());  
Counters counters = currentJob.getCounters();  
Counter counter =          counters.findCounter(TokenizerMapper.MyCounters.TOTAL); 

But when I run the code,
It always gives a

java.lang.NullPointerException at the last line
cluster.getJob(context.getJobID())

It always returns null.

I tried other methods to access the counter incremented in the mapper of the reducer, but without success.

Can someone explain to me what exactly the problem is and how I can access the counter from reducer. I need the value of the total count to calculate the percentage of words.

Here is my driver code.

Configuration conf = new Configuration();
Job job = Job.getInstance(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(FloatWritable.class);
job.setNumReduceTasks(1);
FileInputFormat.addInputPath(job, new Path(args[0]));
FileOutputFormat.setOutputPath(job, new Path(args[1]));
System.exit(job.waitForCompletion(true) ? 0 : 1);

I’m using Hadoop 2.7.0.

You do not need to instantiate the cluster to access counters in the reducer.

In my mapper I have the following code:

// Define a enum in the Mapper class 
enum CustomCounter {Total};

 In the map() method, increment the counter for each record
context.getCounter(CustomCounter.Total).increment(1);

In my reducer, I access the counter as follows:

Counter counter = context.getCounter(CustomCounter.Total);

It suits me perfectly.

Here are my maven dependencies:

<dependencies>
    <dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-common</artifactId>
        <version>2.7.1</version>
    </dependency>
    <dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-mapreduce-client-core</artifactId>
        <version>2.7.1</version>
    </dependency>
    <dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-core</artifactId>
        <version>1.2.1</version>
    </dependency>
</dependencies>