Add warmup counter to EWMA rate

Author: slimjim777

pkg/util/math/rate.go

@@ -12,6 +12,10 @@ import (
 	"go.uber.org/atomic"
 )
 
+const (
+	warmupSamples uint8 = 10
+)
+
 // EwmaRate tracks an exponentially weighted moving average of a per-second rate.
 type EwmaRate struct {
 	newEvents atomic.Int64
@@ -22,6 +26,7 @@ type EwmaRate struct {
 	mutex    sync.RWMutex
 	lastRate float64
 	init     bool
+	count    uint8
 }
 
 func NewEWMARate(alpha float64, interval time.Duration) *EwmaRate {
@@ -35,6 +40,12 @@ func NewEWMARate(alpha float64, interval time.Duration) *EwmaRate {
 func (r *EwmaRate) Rate() float64 {
 	r.mutex.RLock()
 	defer r.mutex.RUnlock()
+
+	// until the first `warmupSamples` have been seen, the moving average is "not ready" to be queried
+	if r.count < warmupSamples {
+		return 0.0
+	}
+
 	return r.lastRate
 }
 
@@ -46,6 +57,10 @@ func (r *EwmaRate) Tick() {
 	r.mutex.Lock()
 	defer r.mutex.Unlock()
 
+	if r.count < warmupSamples {
+		r.count++
+	}
+
 	if r.init {
 		r.lastRate += r.alpha * (instantRate - r.lastRate)
 	} else {

pkg/util/math/rate_test.go

@@ -17,6 +17,17 @@ func TestRate(t *testing.T) {
 		events int
 		want   float64
 	}{
+		// warm-up samples
+		{60, 0},
+		{60, 0},
+		{60, 0},
+		{60, 0},
+		{60, 0},
+		{60, 0},
+		{60, 0},
+		{60, 0},
+		{60, 0},
+
 		{60, 1},
 		{30, 0.9},
 		{0, 0.72},