code: function tock() {
      var tockPeriod = process.hrtime(tickTime);
      var tockPeriodMs = hrtimeAsMs(tockPeriod);
      process.send({
          cmd: 'CLUSTER_PULSE',
          load: tockPeriodMs - pulse,
          memoryUsage: process.memoryUsage()
      });
      tick();
  }
docs: Measures the actual duration of the pulse and transmits health metrics to the supervisor. The load measures the average amount of time that the event loop blocked the scheduled pulse.