Don't spawn a goroutine for every event recording

staging/src/k8s.io/apimachinery/pkg/watch/mux.go

@@ -74,6 +74,22 @@ func NewBroadcaster(queueLength int, fullChannelBehavior FullChannelBehavior) *B
 	return m
 }
 
+// NewLongQueueBroadcaster functions nearly identically to NewBroadcaster,
+// except that the incoming queue is the same size as the outgoing queues
+// (specified by queueLength).
+func NewLongQueueBroadcaster(queueLength int, fullChannelBehavior FullChannelBehavior) *Broadcaster {
+	m := &Broadcaster{
+		watchers:            map[int64]*broadcasterWatcher{},
+		incoming:            make(chan Event, queueLength),
+		stopped:             make(chan struct{}),
+		watchQueueLength:    queueLength,
+		fullChannelBehavior: fullChannelBehavior,
+	}
+	m.distributing.Add(1)
+	go m.loop()
+	return m
+}
+
 const internalRunFunctionMarker = "internal-do-function"
 
 // a function type we can shoehorn into the queue.
@@ -198,6 +214,18 @@ func (m *Broadcaster) Action(action EventType, obj runtime.Object) {
 	m.incoming <- Event{action, obj}
 }
 
+// Action distributes the given event among all watchers, or drops it on the floor
+// if too many incoming actions are queued up.  Returns true if the action was sent,
+// false if dropped.
+func (m *Broadcaster) ActionOrDrop(action EventType, obj runtime.Object) bool {
+	select {
+	case m.incoming <- Event{action, obj}:
+		return true
+	default:
+		return false
+	}
+}
+
 // Shutdown disconnects all watchers (but any queued events will still be distributed).
 // You must not call Action or Watch* after calling Shutdown. This call blocks
 // until all events have been distributed through the outbound channels. Note

staging/src/k8s.io/client-go/tools/record/event.go

@@ -155,21 +155,21 @@ func (a *EventRecorderAdapter) Eventf(regarding, _ runtime.Object, eventtype, re
 // Creates a new event broadcaster.
 func NewBroadcaster() EventBroadcaster {
 	return &eventBroadcasterImpl{
-		Broadcaster:   watch.NewBroadcaster(maxQueuedEvents, watch.DropIfChannelFull),
+		Broadcaster:   watch.NewLongQueueBroadcaster(maxQueuedEvents, watch.DropIfChannelFull),
 		sleepDuration: defaultSleepDuration,
 	}
 }
 
 func NewBroadcasterForTests(sleepDuration time.Duration) EventBroadcaster {
 	return &eventBroadcasterImpl{
-		Broadcaster:   watch.NewBroadcaster(maxQueuedEvents, watch.DropIfChannelFull),
+		Broadcaster:   watch.NewLongQueueBroadcaster(maxQueuedEvents, watch.DropIfChannelFull),
 		sleepDuration: sleepDuration,
 	}
 }
 
 func NewBroadcasterWithCorrelatorOptions(options CorrelatorOptions) EventBroadcaster {
 	return &eventBroadcasterImpl{
-		Broadcaster:   watch.NewBroadcaster(maxQueuedEvents, watch.DropIfChannelFull),
+		Broadcaster:   watch.NewLongQueueBroadcaster(maxQueuedEvents, watch.DropIfChannelFull),
 		sleepDuration: defaultSleepDuration,
 		options:       options,
 	}
@@ -338,11 +338,14 @@ func (recorder *recorderImpl) generateEvent(object runtime.Object, annotations m
 	event := recorder.makeEvent(ref, annotations, eventtype, reason, message)
 	event.Source = recorder.source
 
-	go func() {
-		// NOTE: events should be a non-blocking operation
-		defer utilruntime.HandleCrash()
-		recorder.Action(watch.Added, event)
-	}()
+	// NOTE: events should be a non-blocking operation, but we also need to not
+	// put this in a goroutine, otherwise we'll race to write to a closed channel
+	// when we go to shut down this broadcaster.  Just drop events if we get overloaded,
+	// and log an error if that happens (we've configured the broadcaster to drop
+	// outgoing events anyway).
+	if sent := recorder.ActionOrDrop(watch.Added, event); !sent {
+		klog.Errorf("unable to record event: too many queued events, dropped event %#v", event)
+	}
 }
 
 func (recorder *recorderImpl) Event(object runtime.Object, eventtype, reason, message string) {

staging/src/k8s.io/client-go/tools/record/event_test.go

@@ -21,6 +21,7 @@ import (
 	"fmt"
 	"net/http"
 	"strconv"
+	"sync"
 	"testing"
 	"time"
 
@@ -101,6 +102,29 @@ func OnPatchFactory(testCache map[string]*v1.Event, patchEvent chan<- *v1.Event)
 	}
 }
 
+func TestNonRacyShutdown(t *testing.T) {
+	// Attempt to simulate previously racy conditions, and ensure that no race
+	// occurs: Nominally, calling "Eventf" *followed by* shutdown from the same
+	// thread should be a safe operation, but it's not if we launch recorder.Action
+	// in a goroutine.
+
+	caster := NewBroadcasterForTests(0)
+	clock := clock.NewFakeClock(time.Now())
+	recorder := recorderWithFakeClock(v1.EventSource{Component: "eventTest"}, caster, clock)
+
+	var wg sync.WaitGroup
+	wg.Add(100)
+	for i := 0; i < 100; i++ {
+		go func() {
+			defer wg.Done()
+			recorder.Eventf(&v1.ObjectReference{}, v1.EventTypeNormal, "Started", "blah")
+		}()
+	}
+
+	wg.Wait()
+	caster.Shutdown()
+}
+
 func TestEventf(t *testing.T) {
 	testPod := &v1.Pod{
 		ObjectMeta: metav1.ObjectMeta{