fix(eventbus): block drainer start after shutdown begins

Author: WyRainBow

pkg/core/events/component.go

@@ -92,6 +92,9 @@ func (b *eventBus) Start(_ runtime.Runtime, _ <-chan struct{}) error {
 func (b *eventBus) Subscribe(subscriber Subscriber) error {
 	b.rwMutex.Lock()
 	defer b.rwMutex.Unlock()
+	if b.stopped.Load() {
+		return fmt.Errorf("eventBus already stopped")
+	}
 	rk := subscriber.ResourceKind()
 	states, exists := b.subscriberDir[rk]
 	if !exists {
@@ -216,6 +219,9 @@ func (b *eventBus) WaitForDone() {
 }
 
 func (b *eventBus) launchDrainer(st *subscriberState) {
+	if b.stopped.Load() {
+		return
+	}
 	if !st.drainerStarted.CompareAndSwap(false, true) {
 		return
 	}