Unable to access counter in MapReduce gear class

Question

I am increasing the counter from mappers as follows

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

.

I am trying to get the value of this counter in the gearbox class as follows.

@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

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

which always returns null.

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

Can someone please explain to me what the problem is and how I can access the meters from the gearbox. I need a total score value to calculate the percentage of words.

This 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);

Answer 1

I am using Hadoop 2.7.0.

, .

:

// 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);

, :

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

.

maven:

<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>

Answer 2

JobClient.getJob(conf).getcounters() .