Use informer for kube watcher handling with multiple namespace support (#2594)

* changes to add informer for kube watcher
* code refactor and fix cli issue for deleting watch

pkg/kubewatcher/watchSync.go

@@ -21,16 +21,19 @@ import (
 	"time"
 
 	"go.uber.org/zap"
-	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	k8sCache "k8s.io/client-go/tools/cache"
 
+	fv1 "github.com/fission/fission/pkg/apis/core/v1"
 	"github.com/fission/fission/pkg/generated/clientset/versioned"
+	"github.com/fission/fission/pkg/utils"
 )
 
 type (
 	WatchSync struct {
-		logger      *zap.Logger
-		client      versioned.Interface
-		kubeWatcher *KubeWatcher
+		logger              *zap.Logger
+		client              versioned.Interface
+		kubeWatcher         *KubeWatcher
+		kubeWatcherInformer map[string]k8sCache.SharedIndexInformer
 	}
 )
 
@@ -40,22 +43,28 @@ func MakeWatchSync(ctx context.Context, logger *zap.Logger, client versioned.Int
 		client:      client,
 		kubeWatcher: kubeWatcher,
 	}
-	go ws.syncSvc(ctx)
+	ws.kubeWatcherInformer = utils.GetInformersForNamespaces(client, time.Minute*30, fv1.KubernetesWatchResource)
+	ws.KubeWatcherEventHandlers(ctx)
 	return ws
 }
 
-func (ws *WatchSync) syncSvc(ctx context.Context) {
-	// TODO watch instead of polling
-	for {
-		watches, err := ws.client.CoreV1().KubernetesWatchTriggers(metav1.NamespaceAll).List(ctx, metav1.ListOptions{})
-		if err != nil {
-			ws.logger.Fatal("failed to get Kubernetes watch trigger list", zap.Error(err))
-		}
-
-		err = ws.kubeWatcher.Sync(watches.Items)
-		if err != nil {
-			ws.logger.Fatal("failed to sync watches", zap.Error(err))
-		}
-		time.Sleep(3 * time.Second)
+func (ws *WatchSync) Run(ctx context.Context) {
+	for _, informer := range ws.kubeWatcherInformer {
+		go informer.Run(ctx.Done())
+	}
+}
+
+func (ws *WatchSync) KubeWatcherEventHandlers(ctx context.Context) {
+	for _, informer := range ws.kubeWatcherInformer {
+		informer.AddEventHandler(k8sCache.ResourceEventHandlerFuncs{
+			AddFunc: func(obj interface{}) {
+				objKubeWatcher := obj.(*fv1.KubernetesWatchTrigger)
+				ws.kubeWatcher.addWatch(ctx, objKubeWatcher) //nolint: errCheck
+			},
+			DeleteFunc: func(obj interface{}) {
+				objKubeWatcher := obj.(*fv1.KubernetesWatchTrigger)
+				ws.kubeWatcher.removeWatch(objKubeWatcher) //nolint: errCheck
+			},
+		})
 	}
 }