Account for possible errors returned from `AddEventHandler`

In v0.26.0 client-go's `AddEventHandler` method for informers started
returning a registration handle (that we ignore) and an error that we
now surface up.

controller/api/destination/server.go

@@ -80,10 +80,22 @@ func NewServer(
 		return nil, err
 	}
 
-	endpoints := watcher.NewEndpointsWatcher(k8sAPI, log, enableEndpointSlices)
-	opaquePorts := watcher.NewOpaquePortsWatcher(k8sAPI, log, defaultOpaquePorts)
-	profiles := watcher.NewProfileWatcher(k8sAPI, log)
-	servers := watcher.NewServerWatcher(k8sAPI, log)
+	endpoints, err := watcher.NewEndpointsWatcher(k8sAPI, log, enableEndpointSlices)
+	if err != nil {
+		return nil, err
+	}
+	opaquePorts, err := watcher.NewOpaquePortsWatcher(k8sAPI, log, defaultOpaquePorts)
+	if err != nil {
+		return nil, err
+	}
+	profiles, err := watcher.NewProfileWatcher(k8sAPI, log)
+	if err != nil {
+		return nil, err
+	}
+	servers, err := watcher.NewServerWatcher(k8sAPI, log)
+	if err != nil {
+		return nil, err
+	}
 
 	srv := server{
 		pb.UnimplementedDestinationServer{},

controller/api/destination/test_util.go

@@ -381,10 +381,22 @@ spec:
 		t.Fatalf("initializeIndexers returned an error: %s", err)
 	}
 
-	endpoints := watcher.NewEndpointsWatcher(k8sAPI, log, false)
-	opaquePorts := watcher.NewOpaquePortsWatcher(k8sAPI, log, defaultOpaquePorts)
-	profiles := watcher.NewProfileWatcher(k8sAPI, log)
-	servers := watcher.NewServerWatcher(k8sAPI, log)
+	endpoints, err := watcher.NewEndpointsWatcher(k8sAPI, log, false)
+	if err != nil {
+		t.Fatalf("can't create Endpoints watcher: %s", err)
+	}
+	opaquePorts, err := watcher.NewOpaquePortsWatcher(k8sAPI, log, defaultOpaquePorts)
+	if err != nil {
+		t.Fatalf("can't create opaque ports watcher: %s", err)
+	}
+	profiles, err := watcher.NewProfileWatcher(k8sAPI, log)
+	if err != nil {
+		t.Fatalf("can't create profile watcher: %s", err)
+	}
+	servers, err := watcher.NewServerWatcher(k8sAPI, log)
+	if err != nil {
+		t.Fatalf("can't create Server watcher: %s", err)
+	}
 
 	// Sync after creating watchers so that the the indexers added get updated
 	// properly

controller/api/destination/watcher/endpoints_watcher.go

@@ -134,7 +134,7 @@ var undefinedEndpointPort = Port(0)
 // NewEndpointsWatcher creates an EndpointsWatcher and begins watching the
 // k8sAPI for pod, service, and endpoint changes. An EndpointsWatcher will
 // watch on Endpoints or EndpointSlice resources, depending on cluster configuration.
-func NewEndpointsWatcher(k8sAPI *k8s.API, log *logging.Entry, enableEndpointSlices bool) *EndpointsWatcher {
+func NewEndpointsWatcher(k8sAPI *k8s.API, log *logging.Entry, enableEndpointSlices bool) (*EndpointsWatcher, error) {
 	ew := &EndpointsWatcher{
 		publishers:           make(map[ServiceID]*servicePublisher),
 		k8sAPI:               k8sAPI,
@@ -144,34 +144,46 @@ func NewEndpointsWatcher(k8sAPI *k8s.API, log *logging.Entry, enableEndpointSlic
 		}),
 	}
 
-	k8sAPI.Svc().Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
+	_, err := k8sAPI.Svc().Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
 		AddFunc:    ew.addService,
 		DeleteFunc: ew.deleteService,
 		UpdateFunc: func(_, obj interface{}) { ew.addService(obj) },
 	})
+	if err != nil {
+		return nil, err
+	}
 
-	k8sAPI.Srv().Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
+	_, err = k8sAPI.Srv().Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
 		AddFunc:    ew.addServer,
 		DeleteFunc: ew.deleteServer,
 		UpdateFunc: func(_, obj interface{}) { ew.addServer(obj) },
 	})
+	if err != nil {
+		return nil, err
+	}
 
 	if ew.enableEndpointSlices {
 		ew.log.Debugf("Watching EndpointSlice resources")
-		k8sAPI.ES().Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
+		_, err := k8sAPI.ES().Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
 			AddFunc:    ew.addEndpointSlice,
 			DeleteFunc: ew.deleteEndpointSlice,
 			UpdateFunc: ew.updateEndpointSlice,
 		})
+		if err != nil {
+			return nil, err
+		}
 	} else {
 		ew.log.Debugf("Watching Endpoints resources")
-		k8sAPI.Endpoint().Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
+		_, err = k8sAPI.Endpoint().Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
 			AddFunc:    ew.addEndpoints,
 			DeleteFunc: ew.deleteEndpoints,
 			UpdateFunc: func(_, obj interface{}) { ew.addEndpoints(obj) },
 		})
+		if err != nil {
+			return nil, err
 		}
-	return ew
+	}
+	return ew, nil
 }
 
 ////////////////////////

controller/api/destination/watcher/endpoints_watcher_test.go

@@ -660,7 +660,10 @@ status:
 				t.Fatalf("NewFakeAPI returned an error: %s", err)
 			}
 
-			watcher := NewEndpointsWatcher(k8sAPI, logging.WithField("test", t.Name()), false)
+			watcher, err := NewEndpointsWatcher(k8sAPI, logging.WithField("test", t.Name()), false)
+			if err != nil {
+				t.Fatalf("can't create Endpoints watcher: %s", err)
+			}
 
 			k8sAPI.Sync(nil)
 
@@ -1276,7 +1279,10 @@ status:
 				t.Fatalf("NewFakeAPI returned an error: %s", err)
 			}
 
-			watcher := NewEndpointsWatcher(k8sAPI, logging.WithField("test", t.Name()), true)
+			watcher, err := NewEndpointsWatcher(k8sAPI, logging.WithField("test", t.Name()), true)
+			if err != nil {
+				t.Fatalf("can't create Endpoints watcher: %s", err)
+			}
 
 			k8sAPI.Sync(nil)
 
@@ -1393,7 +1399,10 @@ status:
 				t.Fatalf("NewFakeAPI returned an error: %s", err)
 			}
 
-			watcher := NewEndpointsWatcher(k8sAPI, logging.WithField("test", t.Name()), false)
+			watcher, err := NewEndpointsWatcher(k8sAPI, logging.WithField("test", t.Name()), false)
+			if err != nil {
+				t.Fatalf("can't create Endpoints watcher: %s", err)
+			}
 
 			k8sAPI.Sync(nil)
 
@@ -1514,7 +1523,10 @@ status:
 				t.Fatalf("NewFakeAPI returned an error: %s", err)
 			}
 
-			watcher := NewEndpointsWatcher(k8sAPI, logging.WithField("test", t.Name()), true)
+			watcher, err := NewEndpointsWatcher(k8sAPI, logging.WithField("test", t.Name()), true)
+			if err != nil {
+				t.Fatalf("can't create Endpoints watcher: %s", err)
+			}
 
 			k8sAPI.Sync(nil)
 
@@ -1741,7 +1753,10 @@ subsets:
 				t.Fatalf("NewFakeAPI returned an error: %s", err)
 			}
 
-			watcher := NewEndpointsWatcher(k8sAPI, logging.WithField("test", t.Name()), tt.enableEndpointSlices)
+			watcher, err := NewEndpointsWatcher(k8sAPI, logging.WithField("test", t.Name()), tt.enableEndpointSlices)
+			if err != nil {
+				t.Fatalf("can't create Endpoints watcher: %s", err)
+			}
 
 			k8sAPI.Sync(nil)
 
@@ -1901,7 +1916,10 @@ subsets:
 				t.Fatalf("NewFakeAPI returned an error: %s", err)
 			}
 
-			watcher := NewEndpointsWatcher(k8sAPI, logging.WithField("test", t.Name()), false)
+			watcher, err := NewEndpointsWatcher(k8sAPI, logging.WithField("test", t.Name()), false)
+			if err != nil {
+				t.Fatalf("can't create Endpoints watcher: %s", err)
+			}
 
 			k8sAPI.Sync(nil)
 
@@ -2024,7 +2042,10 @@ status:
 				t.Fatalf("NewFakeAPI returned an error: %s", err)
 			}
 
-			watcher := NewEndpointsWatcher(k8sAPI, logging.WithField("test", t.Name()), false)
+			watcher, err := NewEndpointsWatcher(k8sAPI, logging.WithField("test", t.Name()), false)
+			if err != nil {
+				t.Fatalf("can't create Endpoints watcher: %s", err)
+			}
 
 			k8sAPI.Sync(nil)
 

controller/api/destination/watcher/opaque_ports_watcher.go

@@ -37,19 +37,23 @@ type (
 
 // NewOpaquePortsWatcher creates a OpaquePortsWatcher and begins watching for
 // k8sAPI for service changes.
-func NewOpaquePortsWatcher(k8sAPI *k8s.API, log *logging.Entry, opaquePorts map[uint32]struct{}) *OpaquePortsWatcher {
+func NewOpaquePortsWatcher(k8sAPI *k8s.API, log *logging.Entry, opaquePorts map[uint32]struct{}) (*OpaquePortsWatcher, error) {
 	opw := &OpaquePortsWatcher{
 		subscriptions:      make(map[ServiceID]*svcSubscriptions),
 		k8sAPI:             k8sAPI,
 		log:                log.WithField("component", "opaque-ports-watcher"),
 		defaultOpaquePorts: opaquePorts,
 	}
-	k8sAPI.Svc().Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
+	_, err := k8sAPI.Svc().Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
 		AddFunc:    opw.addService,
 		DeleteFunc: opw.deleteService,
 		UpdateFunc: func(_, obj interface{}) { opw.addService(obj) },
 	})
-	return opw
+	if err != nil {
+		return nil, err
+	}
+
+	return opw, nil
 }
 
 // Subscribe subscribes a listener to a service; each time the service

controller/api/destination/watcher/opaque_ports_watcher_test.go

@@ -218,7 +218,10 @@ func TestOpaquePortsWatcher(t *testing.T) {
 		if err != nil {
 			t.Fatalf("NewFakeAPI returned an error: %s", err)
 		}
-		watcher := NewOpaquePortsWatcher(k8sAPI, logging.WithField("test", t.Name()), defaultOpaquePorts)
+		watcher, err := NewOpaquePortsWatcher(k8sAPI, logging.WithField("test", t.Name()), defaultOpaquePorts)
+		if err != nil {
+			t.Fatalf("can't create opaque ports watcher: %s", err)
+		}
 		k8sAPI.Sync(nil)
 		listener := newTestOpaquePortsListener()
 		watcher.Subscribe(tt.service, listener)

controller/api/destination/watcher/profile_watcher.go

@@ -44,22 +44,25 @@ var profileVecs = newMetricsVecs("profile", []string{"namespace", "profile"})
 
 // NewProfileWatcher creates a ProfileWatcher and begins watching the k8sAPI for
 // service profile changes.
-func NewProfileWatcher(k8sAPI *k8s.API, log *logging.Entry) *ProfileWatcher {
+func NewProfileWatcher(k8sAPI *k8s.API, log *logging.Entry) (*ProfileWatcher, error) {
 	watcher := &ProfileWatcher{
 		profileLister: k8sAPI.SP().Lister(),
 		profiles:      make(map[ProfileID]*profilePublisher),
 		log:           log.WithField("component", "profile-watcher"),
 	}
 
-	k8sAPI.SP().Informer().AddEventHandler(
+	_, err := k8sAPI.SP().Informer().AddEventHandler(
 		cache.ResourceEventHandlerFuncs{
 			AddFunc:    watcher.addProfile,
 			UpdateFunc: watcher.updateProfile,
 			DeleteFunc: watcher.deleteProfile,
 		},
 	)
+	if err != nil {
+		return nil, err
+	}
 
-	return watcher
+	return watcher, nil
 }
 
 //////////////////////

controller/api/destination/watcher/profile_watcher_test.go

@@ -84,7 +84,10 @@ func TestProfileWatcherUpdates(t *testing.T) {
 				t.Fatalf("NewFakeAPI returned an error: %s", err)
 			}
 
-			watcher := NewProfileWatcher(k8sAPI, logging.WithField("test", t.Name()))
+			watcher, err := NewProfileWatcher(k8sAPI, logging.WithField("test", t.Name()))
+			if err != nil {
+				t.Fatalf("can't create profile watcher: %s", err)
+			}
 
 			k8sAPI.Sync(nil)
 
@@ -136,7 +139,10 @@ func TestProfileWatcherDeletes(t *testing.T) {
 				t.Fatalf("NewFakeAPI returned an error: %s", err)
 			}
 
-			watcher := NewProfileWatcher(k8sAPI, logging.WithField("test", t.Name()))
+			watcher, err := NewProfileWatcher(k8sAPI, logging.WithField("test", t.Name()))
+			if err != nil {
+				t.Fatalf("can't create profile watcher: %s", err)
+			}
 			k8sAPI.Sync(nil)
 
 			listener := NewDeletingProfileListener()

controller/api/destination/watcher/server_watcher.go

@@ -37,18 +37,22 @@ type ServerUpdateListener interface {
 }
 
 // NewServerWatcher creates a new ServerWatcher.
-func NewServerWatcher(k8sAPI *k8s.API, log *logging.Entry) *ServerWatcher {
+func NewServerWatcher(k8sAPI *k8s.API, log *logging.Entry) (*ServerWatcher, error) {
 	sw := &ServerWatcher{
 		subscriptions: make(map[podPort][]ServerUpdateListener),
 		k8sAPI:        k8sAPI,
 		log:           log,
 	}
-	k8sAPI.Srv().Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
+	_, err := k8sAPI.Srv().Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
 		AddFunc:    sw.addServer,
 		DeleteFunc: sw.deleteServer,
 		UpdateFunc: func(_, obj interface{}) { sw.addServer(obj) },
 	})
-	return sw
+	if err != nil {
+		return nil, err
+	}
+
+	return sw, nil
 }
 
 // Subscribe subscribes a listener for any Server updates that may select the

multicluster/service-mirror/cluster_watcher.go

@@ -782,7 +782,7 @@ func (rcsw *RemoteClusterServiceWatcher) processEvents(ctx context.Context) {
 func (rcsw *RemoteClusterServiceWatcher) Start(ctx context.Context) error {
 	rcsw.remoteAPIClient.Sync(rcsw.stopper)
 	rcsw.eventsQueue.Add(&OrphanedServicesGcTriggered{})
-	rcsw.remoteAPIClient.Svc().Informer().AddEventHandler(
+	_, err := rcsw.remoteAPIClient.Svc().Informer().AddEventHandler(
 		cache.ResourceEventHandlerFuncs{
 			AddFunc: func(svc interface{}) {
 				rcsw.eventsQueue.Add(&OnAddCalled{svc.(*corev1.Service)})
@@ -808,8 +808,11 @@ func (rcsw *RemoteClusterServiceWatcher) Start(ctx context.Context) error {
 			},
 		},
 	)
+	if err != nil {
+		return err
+	}
 
-	rcsw.remoteAPIClient.Endpoint().Informer().AddEventHandler(
+	_, err = rcsw.remoteAPIClient.Endpoint().Informer().AddEventHandler(
 		cache.ResourceEventHandlerFuncs{
 			// AddFunc only relevant for exported headless endpoints
 			AddFunc: func(obj interface{}) {
@@ -845,14 +848,20 @@ func (rcsw *RemoteClusterServiceWatcher) Start(ctx context.Context) error {
 			},
 		},
 	)
+	if err != nil {
+		return err
+	}
 
-	rcsw.localAPIClient.NS().Informer().AddEventHandler(
+	_, err = rcsw.localAPIClient.NS().Informer().AddEventHandler(
 		cache.ResourceEventHandlerFuncs{
 			AddFunc: func(obj interface{}) {
 				rcsw.eventsQueue.Add(&OnLocalNamespaceAdded{obj.(*corev1.Namespace)})
 			},
 		},
 	)
+	if err != nil {
+		return err
+	}
 
 	go rcsw.processEvents(ctx)