Fix memory leak in fleet autoscaler webhook HTTP client

- Change fasThread.state from fasState (value) to *fasState (pointer) so
  the cached http.Client persists across sync cycles instead of being
  recreated on every iteration.
- Drain HTTP response body before closing to allow http.Transport to
  reuse connections, preventing unbounded connection growth.

Author: markmandel

pkg/fleetautoscalers/controller.go

@@ -72,7 +72,7 @@ type fasState struct {
 // fasThread is used for tracking each Fleet's autoscaling jobs
 type fasThread struct {
 	cancel     context.CancelFunc
-	state      fasState
+	state      *fasState
 	generation int64
 }
 
@@ -360,7 +360,7 @@ func (c *Controller) syncFleetAutoscaler(ctx context.Context, key string) error
 
 	currentReplicas := fleet.Status.Replicas
 	gameServerNamespacedLister := c.gameServerLister.GameServers(fleet.ObjectMeta.Namespace)
-	desiredReplicas, scalingLimited, err := computeDesiredFleetSize(ctx, &thread.state, fas.Spec.Policy, fleet, gameServerNamespacedLister, c.counter.Counts(), &fasLog)
+	desiredReplicas, scalingLimited, err := computeDesiredFleetSize(ctx, thread.state, fas.Spec.Policy, fleet, gameServerNamespacedLister, c.counter.Counts(), &fasLog)
 
 	// If the err is not nil and not an inactive schedule error (ignorable in this case), then record the event
 	if err != nil {
@@ -498,7 +498,7 @@ func (c *Controller) addFasThread(fas *autoscalingv1.FleetAutoscaler, lock bool)
 	thread := fasThread{
 		cancel:     cancel,
 		generation: fas.Generation,
-		state:      fasState{},
+		state:      &fasState{},
 	}
 
 	if lock {

pkg/fleetautoscalers/controller_test.go

@@ -1178,9 +1178,9 @@ func TestControllerCleanFasThreads(t *testing.T) {
 
 	c.fasThreadMutex.Lock()
 	c.fasThreads = map[types.UID]fasThread{
-		"1":                {func() {}, fasState{}, 1},
-		"2":                {func() {}, fasState{}, 2},
-		fas.ObjectMeta.UID: {func() {}, fasState{}, 3},
+		"1":                {func() {}, &fasState{}, 1},
+		"2":                {func() {}, &fasState{}, 2},
+		fas.ObjectMeta.UID: {func() {}, &fasState{}, 3},
 	}
 	c.fasThreadMutex.Unlock()
 

pkg/fleetautoscalers/fleetautoscalers.go

@@ -319,6 +319,8 @@ func applyWebhookPolicy(state *fasState, w *autoscalingv1.URLConfiguration, f *a
 		return 0, false, err
 	}
 	defer func() {
+		// Drain any unread body so the underlying connection can be reused by http.Transport.
+		_, _ = io.Copy(io.Discard, res.Body)
 		if cerr := res.Body.Close(); cerr != nil {
 			if err != nil {
 				err = errors.Wrap(err, cerr.Error())