code: public Counters readCounters(JobID jobId) {
      Counters counters = null;
      if (active) {
        try {
          FSDataInputStream dataIn = getJobInfoFile(jobId);
          if (dataIn != null) {
            readJobStatus(dataIn);
            readJobProfile(dataIn);
            counters = readCounters(dataIn);
            dataIn.close();
          }
        } catch (IOException ex) {
          LOG.warn("Could not read [" + jobId + "] job counters : " + ex, ex);
        }
      }
      return counters;
    }
docs: This method retrieves Counters information from DFS stored using
  store method.
  
  @param jobId the jobId for which Counters is queried
  @return Counters object, null if not able to retrieve