code: private void incrementAttemptUnprotected() {
      attempt++;
      currentAttemptId = new TaskAttemptID(new TaskID(attemptJobId,
          currentAttemptId.isMap(), currentAttemptId.getTaskID().getId()),
          attempt);
    }
docs: Increment the attempt number for launching a remote corona job tracker.
  Must be called only when holding the object lock.