code: func (s *volumeStatCalculator) StartOnce() *volumeStatCalculator {
  	s.startO.Do(func() {
  		go wait.JitterUntil(func() {
  			s.calcAndStoreStats()
  		}, s.jitterPeriod, 1.0, true, s.stopChannel)
  	})
  	return s
  }
docs: // StartOnce starts pod volume calc that will occur periodically in the background until s.StopOnce is called