fix an error when karmada-controller-manager restart

Signed-off-by: changzhen <changzhen5@huawei.com>

pkg/controllers/mcs/service_export_controller.go

@@ -285,11 +285,6 @@ func (c *ServiceExportController) handleEndpointSliceEvent(endpointSliceKey keys
 		return err
 	}
 
-	if endpointSliceObj == nil {
-		klog.V(2).Infof("Ignore the event key %s which not listened by karmada.", endpointSliceKey)
-		return nil
-	}
-
 	if err = c.reportEndpointSliceWithEndpointSliceCreateOrUpdate(endpointSliceKey.Cluster, endpointSliceObj); err != nil {
 		klog.Errorf("Failed to handle endpointSlice(%s) event, Error: %v",
 			endpointSliceKey.NamespaceKey(), err)

pkg/controllers/status/workstatus_controller.go

@@ -159,12 +159,6 @@ func (c *WorkStatusController) syncWorkStatus(key util.QueueKey) error {
 		return err
 	}
 
-	if obj == nil {
-		// Ignore the object which not managed by current karmada.
-		klog.V(2).Infof("Ignore the event key %s which not managed by karmada.", key)
-		return nil
-	}
-
 	workNamespace := util.GetLabelValue(obj.GetLabels(), workv1alpha1.WorkNamespaceLabel)
 	workName := util.GetLabelValue(obj.GetLabels(), workv1alpha1.WorkNameLabel)
 	if len(workNamespace) == 0 || len(workName) == 0 {

pkg/util/helper/cache.go

@@ -1,6 +1,8 @@
 package helper
 
 import (
+	"fmt"
+
 	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	"k8s.io/apimachinery/pkg/api/meta"
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
@@ -23,7 +25,11 @@ func GetObjectFromCache(restMapper meta.RESTMapper, manager informermanager.Mult
 
 	singleClusterManager := manager.GetSingleClusterManager(fedKey.Cluster)
 	if singleClusterManager == nil {
-		return nil, nil
+		// That may happen in case of multi-controllers sharing one informer. For example:
+		// controller-A takes responsibility of initialize informer for clusters, but controller-B consumes
+		// the informer before the initialization.
+		// Usually this error will be eliminated during the controller reconciling loop.
+		return nil, fmt.Errorf("the informer of cluster(%s) has not been initialized", fedKey.Cluster)
 	}
 	var obj runtime.Object
 	lister := singleClusterManager.Lister(gvr)