code: public Counters getCounters() {
      Counters result = new Counters();
      synchronized (this) {
        result.incrAllCounters(getJobCounters());
      }
  
      incrementTaskCounters(result, maps);
      return incrementTaskCounters(result, reduces);
    }
docs: Returns the total job counters, by adding together the job,
  the map and the reduce counters.