How to Access the built-in counters in hadoop MapReduce - hadoop

Question

I have been working on to find the numbers of total records parsed by all the mappers using the MAP_INPUT_RECORDS variable.
Here is the code I am using :
Counters counters = job.getCounters();
for (CounterGroup group : counters) {
System.out.println("* Counter Group: " + group.getDisplayName() + " (" + group.getName() + ")");
System.out.println(" number of counters in this group: " + group.size());
for (Counter counter : group) {
System.out.println(" - " + counter.getDisplayName() + ": " + counter.getName() + ": "+counter.getValue());
}
}
Also, I tried using the following code snippet :
{
Counters counters = job.getCounters();
int recordCountData = (int)
//counters.getGroup("org.apache.hadoop.mapred.Task$Counter").findCounter("MAP_INPUT_RECORDS").getValue();
int recordCountData = (int) counters.findCounter(
"org.apache.hadoop.mapred.Task$Counter","MAP_INPUT_RECORDS")
.getValue();
}
But everytime it throws the following error :
Exception in thread "main" java.lang.IncompatibleClassChangeError: Found interface org.apache.hadoop.mapreduce.CounterGroup, but class was expected
at com.ssga.common.riskmeasures.validation.mr.RiskMeasuresValidationDriver.run(RiskMeasuresValidationDriver.java:169)
at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:70)
at com.ssga.common.riskmeasures.validation.mr.RiskMeasuresValidationDriver.main(RiskMeasuresValidationDriver.java:189)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.hadoop.util.RunJar.main(RunJar.java:212)
PS : I am trying to use the above mentioned approaches after job.waitForCompletion(true) in the Driver class.
Any approach on how I can resolve this issue?
Thanks in advance.
Akhilesh

Answer 1

"The new API favors abstract classes over interfaces, since these are easier to evolve. For example, you can add a method (with a default implementation) to an abstract class without breaking old implementations of the class2. For example, the Mapper and Reducer interfaces in the old API are abstract classes in the new API."
"The new API is in the org.apache.hadoop.mapreduce package (and subpackages).
The old API can still be found in org.apache.hadoop.mapred."
-Hadoop the Definitive Guide by Tom White, 3rd Edition, Page 28
Check your mapper and reducer, use them as classes.