layer1: share managed namespace watcher startup

pkg/utils/namespace_manager.go

@@ -9,7 +9,12 @@ import (
 
 	"go.uber.org/zap"
 	corev1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	k8sInformers "k8s.io/client-go/informers"
+	"k8s.io/client-go/kubernetes"
 	k8sCache "k8s.io/client-go/tools/cache"
+
+	managerPkg "github.com/fission/fission/pkg/utils/manager"
 )
 
 type NamespaceSubscriber interface {
@@ -207,6 +212,28 @@ func NewNamespaceWatcherEventHandlers(ctx context.Context, logger *zap.Logger, c
 	}
 }
 
+func StartManagedNamespaceWatcher(ctx context.Context, logger *zap.Logger, component string, kubeClient kubernetes.Interface, mgr managerPkg.Interface, handlers k8sCache.ResourceEventHandlerFuncs) {
+	factory := k8sInformers.NewSharedInformerFactoryWithOptions(
+		kubeClient,
+		30*time.Minute,
+		k8sInformers.WithTweakListOptions(func(opts *metav1.ListOptions) {
+			opts.LabelSelector = ManagedNamespaceLabelSelector()
+		}),
+	)
+
+	nsInformer := factory.Core().V1().Namespaces().Informer()
+	_, _ = nsInformer.AddEventHandler(handlers)
+
+	mgr.Add(ctx, func(ctx context.Context) {
+		logger.Info(component+": started", zap.String("label", ManagedNamespaceLabelSelector()))
+		factory.Start(ctx.Done())
+		factory.WaitForCacheSync(ctx.Done())
+		logger.Info(component + ": cache synced — watching for new namespaces")
+		<-ctx.Done()
+		logger.Info(component + ": stopped")
+	})
+}
+
 func (m *inMemoryNamespaceManager) Subscribe(subscriber NamespaceSubscriber) {
 	m.mu.Lock()
 	defer m.mu.Unlock()