storage/remote/ewma.go
func (r *ewmaRate) rate() float64 {
	r.mutex.Lock()
	defer r.mutex.Unlock()
	return r.lastRate
}
func (r *ewmaRate) rate() float64 {
	r.mutex.Lock()
	defer r.mutex.Unlock()
	return r.lastRate
}
// rate returns the per-second rate.