adding clear function to histogram

z/histogram.go

@@ -153,11 +153,14 @@ func (histogram *HistogramData) String() string {
 // Percentile returns the percentile value for the histogram.
 // value of p should be between [0.0-1.0]
 func (histogram *HistogramData) Percentile(p float64) float64 {
+	if histogram == nil {
+		return 0
+	}
+
 	if histogram.Count == 0 {
 		// if no data return the minimum range
 		return histogram.Bounds[0]
 	}
-
 	pval := int64(float64(histogram.Count) * p)
 	for i, v := range histogram.CountPerBucket {
 		pval = pval - v
@@ -169,5 +172,18 @@ func (histogram *HistogramData) Percentile(p float64) float64 {
 		}
 	}
 	// default return should be the max range
-	return histogram.Bounds[len(histogram.Bounds) - 1]
-}
+	return histogram.Bounds[len(histogram.Bounds)-1]
+}
+
+// Clear reset the histogram. Helpful in situations where we need to reset the metrics
+func (histogram *HistogramData) Clear() {
+	if histogram == nil {
+		return
+	}
+
+	histogram.Count = 0
+	histogram.CountPerBucket = make([]int64, len(histogram.Bounds)+1)
+	histogram.Sum = 0
+	histogram.Max = 0
+	histogram.Min = math.MaxInt64
+}

z/histogram_test.go

@@ -1,14 +1,15 @@
 package z
 
 import (
-	"github.com/stretchr/testify/require"
 	"math"
 	"testing"
+
+	"github.com/stretchr/testify/require"
 )
 
 func TestPercentile00(t *testing.T) {
 	size := int(math.Ceil((float64(514) - float64(32)) / float64(4)))
-	bounds := make([]float64, size + 1)
+	bounds := make([]float64, size+1)
 	for i := range bounds {
 		if i == 0 {
 			bounds[0] = 32
@@ -22,8 +23,8 @@ func TestPercentile00(t *testing.T) {
 	}
 
 	h := NewHistogramData(bounds)
-	for v := 16; v <= 1024; v= v+4 {
-		for i:=0; i < 1000; i++ {
+	for v := 16; v <= 1024; v = v + 4 {
+		for i := 0; i < 1000; i++ {
 			h.Update(int64(v))
 		}
 	}
@@ -33,7 +34,7 @@ func TestPercentile00(t *testing.T) {
 
 func TestPercentile99(t *testing.T) {
 	size := int(math.Ceil((float64(514) - float64(32)) / float64(4)))
-	bounds := make([]float64, size + 1)
+	bounds := make([]float64, size+1)
 	for i := range bounds {
 		if i == 0 {
 			bounds[0] = 32
@@ -46,18 +47,18 @@ func TestPercentile99(t *testing.T) {
 		bounds[i] = bounds[i-1] + 4
 	}
 	h := NewHistogramData(bounds)
-	for v := 16; v <= 1024; v= v+4 {
-		for i:=0; i < 1000; i++ {
+	for v := 16; v <= 512; v = v + 4 {
+		for i := 0; i < 1000; i++ {
 			h.Update(int64(v))
 		}
 	}
 
-	require.Equal(t, h.Percentile(0.99), 514.0)
+	require.Equal(t, h.Percentile(0.99), 512.0)
 }
 
 func TestPercentile100(t *testing.T) {
 	size := int(math.Ceil((float64(514) - float64(32)) / float64(4)))
-	bounds := make([]float64, size + 1)
+	bounds := make([]float64, size+1)
 	for i := range bounds {
 		if i == 0 {
 			bounds[0] = 32
@@ -70,11 +71,10 @@ func TestPercentile100(t *testing.T) {
 		bounds[i] = bounds[i-1] + 4
 	}
 	h := NewHistogramData(bounds)
-	for v := 16; v <= 1024; v= v+4 {
-		for i:=0; i < 1000; i++ {
+	for v := 16; v <= 1024; v = v + 4 {
+		for i := 0; i < 1000; i++ {
 			h.Update(int64(v))
 		}
 	}
 	require.Equal(t, h.Percentile(1.0), 514.0)
 }
-