metrics: use slices package for sorting (#27493)

Co-authored-by: Felix Lange <fjl@twurst.com>

metrics/resetting_timer.go

@@ -2,9 +2,10 @@ package metrics
 
 import (
 	"math"
-	"sort"
 	"sync"
 	"time"
+
+	"golang.org/x/exp/slices"
 )
 
 // Initial slice capacity for the values stored in a ResettingTimer
@@ -186,7 +187,7 @@ func (t *ResettingTimerSnapshot) Mean() float64 {
 }
 
 func (t *ResettingTimerSnapshot) calc(percentiles []float64) {
-	sort.Sort(Int64Slice(t.values))
+	slices.Sort(t.values)
 
 	count := len(t.values)
 	if count > 0 {
@@ -232,10 +233,3 @@ func (t *ResettingTimerSnapshot) calc(percentiles []float64) {
 
 	t.calculated = true
 }
-
-// Int64Slice attaches the methods of sort.Interface to []int64, sorting in increasing order.
-type Int64Slice []int64
-
-func (s Int64Slice) Len() int           { return len(s) }
-func (s Int64Slice) Less(i, j int) bool { return s[i] < s[j] }
-func (s Int64Slice) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }

metrics/sample.go

@@ -3,9 +3,10 @@ package metrics
 import (
 	"math"
 	"math/rand"
-	"sort"
 	"sync"
 	"time"
+
+	"golang.org/x/exp/slices"
 )
 
 const rescaleThreshold = time.Hour
@@ -282,17 +283,17 @@ func SampleMin(values []int64) int64 {
 }
 
 // SamplePercentiles returns an arbitrary percentile of the slice of int64.
-func SamplePercentile(values int64Slice, p float64) float64 {
+func SamplePercentile(values []int64, p float64) float64 {
 	return SamplePercentiles(values, []float64{p})[0]
 }
 
 // SamplePercentiles returns a slice of arbitrary percentiles of the slice of
 // int64.
-func SamplePercentiles(values int64Slice, ps []float64) []float64 {
+func SamplePercentiles(values []int64, ps []float64) []float64 {
 	scores := make([]float64, len(ps))
 	size := len(values)
 	if size > 0 {
-		sort.Sort(values)
+		slices.Sort(values)
 		for i, p := range ps {
 			pos := p * float64(size+1)
 			if pos < 1.0 {
@@ -633,9 +634,3 @@ func (h *expDecaySampleHeap) down(i, n int) {
 		i = j
 	}
 }
-
-type int64Slice []int64
-
-func (p int64Slice) Len() int           { return len(p) }
-func (p int64Slice) Less(i, j int) bool { return p[i] < p[j] }
-func (p int64Slice) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }

metrics/writer.go

@@ -3,8 +3,9 @@ package metrics
 import (
 	"fmt"
 	"io"
-	"sort"
 	"time"
+
+	"golang.org/x/exp/slices"
 )
 
 // Write sorts writes each metric in the given registry periodically to the
@@ -18,12 +19,12 @@ func Write(r Registry, d time.Duration, w io.Writer) {
 // WriteOnce sorts and writes metrics in the given registry to the given
 // io.Writer.
 func WriteOnce(r Registry, w io.Writer) {
-	var namedMetrics namedMetricSlice
+	var namedMetrics []namedMetric
 	r.Each(func(name string, i interface{}) {
 		namedMetrics = append(namedMetrics, namedMetric{name, i})
 	})
 
-	sort.Sort(namedMetrics)
+	slices.SortFunc(namedMetrics, namedMetric.less)
 	for _, namedMetric := range namedMetrics {
 		switch metric := namedMetric.m.(type) {
 		case Counter:
@@ -91,13 +92,6 @@ type namedMetric struct {
 	m    interface{}
 }
 
-// namedMetricSlice is a slice of namedMetrics that implements sort.Interface.
-type namedMetricSlice []namedMetric
-
-func (nms namedMetricSlice) Len() int { return len(nms) }
-
-func (nms namedMetricSlice) Swap(i, j int) { nms[i], nms[j] = nms[j], nms[i] }
-
-func (nms namedMetricSlice) Less(i, j int) bool {
-	return nms[i].name < nms[j].name
+func (m namedMetric) less(other namedMetric) bool {
+	return m.name < other.name
 }

metrics/writer_test.go

@@ -1,19 +1,20 @@
 package metrics
 
 import (
-	"sort"
 	"testing"
+
+	"golang.org/x/exp/slices"
 )
 
 func TestMetricsSorting(t *testing.T) {
-	var namedMetrics = namedMetricSlice{
+	var namedMetrics = []namedMetric{
 		{name: "zzz"},
 		{name: "bbb"},
 		{name: "fff"},
 		{name: "ggg"},
 	}
 
-	sort.Sort(namedMetrics)
+	slices.SortFunc(namedMetrics, namedMetric.less)
 	for i, name := range []string{"bbb", "fff", "ggg", "zzz"} {
 		if namedMetrics[i].name != name {
 			t.Fail()