Replace calls to time.After with time.NewTimer for explicit stopping

pkg/client/cache/reflector.go

@@ -106,17 +106,24 @@ var (
 	errorStopRequested = errors.New("Stop requested")
 )
 
-// resyncChan returns a channel which will receive something when a resync is required.
-func (r *Reflector) resyncChan() <-chan time.Time {
+// resyncChan returns a channel which will receive something when a resync is
+// required, and a cleanup function.
+func (r *Reflector) resyncChan() (<-chan time.Time, func() bool) {
 	if r.resyncPeriod == 0 {
-		return neverExitWatch
+		return neverExitWatch, func() bool { return false }
 	}
-	return time.After(r.resyncPeriod)
+	// The cleanup function is required: imagine the scenario where watches
+	// always fail so we end up listing frequently. Then, if we don't
+	// manually stop the timer, we could end up with many timers active
+	// concurrently.
+	t := time.NewTimer(r.resyncPeriod)
+	return t.C, t.Stop
 }
 
 func (r *Reflector) listAndWatch(stopCh <-chan struct{}) {
 	var resourceVersion string
-	resyncCh := r.resyncChan()
+	resyncCh, cleanup := r.resyncChan()
+	defer cleanup()
 
 	list, err := r.listerWatcher.List()
 	if err != nil {

pkg/client/cache/reflector_test.go

@@ -18,6 +18,7 @@ package cache
 
 import (
 	"fmt"
+	"math/rand"
 	"strconv"
 	"testing"
 	"time"
@@ -95,7 +96,8 @@ func TestRunUntil(t *testing.T) {
 func TestReflector_resyncChan(t *testing.T) {
 	s := NewStore(MetaNamespaceKeyFunc)
 	g := NewReflector(&testLW{}, &api.Pod{}, s, time.Millisecond)
-	a, b := g.resyncChan(), time.After(100*time.Millisecond)
+	a, _ := g.resyncChan()
+	b := time.After(100 * time.Millisecond)
 	select {
 	case <-a:
 		t.Logf("got timeout as expected")
@@ -104,6 +106,18 @@ func TestReflector_resyncChan(t *testing.T) {
 	}
 }
 
+func BenchmarkReflector_resyncChanMany(b *testing.B) {
+	s := NewStore(MetaNamespaceKeyFunc)
+	g := NewReflector(&testLW{}, &api.Pod{}, s, 25*time.Millisecond)
+	// The improvement to this (calling the timer's Stop() method) makes
+	// this benchmark about 40% faster.
+	for i := 0; i < b.N; i++ {
+		g.resyncPeriod = time.Duration(rand.Float64() * float64(time.Millisecond) * 25)
+		_, stop := g.resyncChan()
+		stop()
+	}
+}
+
 func TestReflector_watchHandlerError(t *testing.T) {
 	s := NewStore(MetaNamespaceKeyFunc)
 	g := NewReflector(&testLW{}, &api.Pod{}, s, 0)