Virtual kubelet: do not start reflection with 0 workers

pkg/virtualKubelet/reflection/generic/reflector.go

@@ -36,6 +36,7 @@ import (
 )
 
 var _ manager.Reflector = (*reflector)(nil)
+var _ manager.Reflector = (*dummyreflector)(nil)
 
 // NamespacedReflectorFactoryFunc represents the function type to create a new NamespacedReflector.
 type NamespacedReflectorFactoryFunc func(*options.NamespacedOpts) manager.NamespacedReflector
@@ -59,8 +60,18 @@ type reflector struct {
 	fallbackFactory   FallbackReflectorFactoryFunc
 }
 
-// NewReflector returns a new reflector to implement the reflection towards a remote clusters.
+// NewReflector returns a new reflector to implement the reflection towards a remote clusters, of a dummy one if no workers are specified.
 func NewReflector(name string, namespaced NamespacedReflectorFactoryFunc, fallback FallbackReflectorFactoryFunc, workers uint) manager.Reflector {
+	if workers == 0 {
+		// Return a dummy reflector in case no workers are specified, to avoid starting the working queue and registering the infromers.
+		return &dummyreflector{name: name}
+	}
+
+	return newReflector(name, namespaced, fallback, workers)
+}
+
+// newReflector returns a new reflector to implement the reflection towards a remote clusters.
+func newReflector(name string, namespaced NamespacedReflectorFactoryFunc, fallback FallbackReflectorFactoryFunc, workers uint) manager.Reflector {
 	return &reflector{
 		name:    name,
 		workers: workers,
@@ -258,3 +269,22 @@ func NamespacedKeyer(namespace string) func(metadata metav1.Object) types.Namesp
 func WithoutFallback() FallbackReflectorFactoryFunc {
 	return func(ro *options.ReflectorOpts) manager.FallbackReflector { return nil }
 }
+
+type dummyreflector struct{ name string }
+
+// Start starts the dummy reflector (no-op).
+func (dr *dummyreflector) Start(ctx context.Context, opts *options.ReflectorOpts) {
+	klog.Infof("Skipping starting the %v reflector, as no workers are configured", dr.name)
+}
+
+// StartNamespace starts the reflection for the given namespace (no-op).
+func (dr *dummyreflector) StartNamespace(opts *options.NamespacedOpts) {
+	klog.Infof("Skipping starting the %v reflection between local namespace %q and remote namespace %q, as no workers are configured",
+		dr.name, opts.LocalNamespace, opts.RemoteNamespace)
+}
+
+// StopNamespace stops the reflection for the given namespace (no-op).
+func (dr *dummyreflector) StopNamespace(local, remote string) {
+	klog.Infof("Skipping stopping the %v reflection between local namespace %q and remote namespace %q, as no workers are configured",
+		dr.name, local, remote)
+}

pkg/virtualKubelet/reflection/generic/reflector_test.go

@@ -19,6 +19,7 @@ import (
 
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
+	. "github.com/onsi/gomega/gstruct"
 	corev1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/types"
@@ -62,10 +63,27 @@ var _ = Describe("Reflector tests", func() {
 		})
 
 		Context("a new reflector is created", func() {
-			BeforeEach(func() { workers = 10 })
 			JustBeforeEach(func() {
 				rfl = NewReflector(reflectorName, NewFakeNamespacedReflector, NewFakeFallbackReflector, workers)
 			})
+
+			When("no workers are specified", func() {
+				BeforeEach(func() { workers = 0 })
+				It("should return a dummy reflector", func() { Expect(rfl).To(PointTo(BeAssignableToTypeOf(dummyreflector{}))) })
+			})
+
+			When("at least one worker is specified", func() {
+				BeforeEach(func() { workers = 1 })
+				It("should return a real reflector", func() { Expect(rfl).To(PointTo(BeAssignableToTypeOf(reflector{}))) })
+			})
+		})
+
+		Context("a new real reflector is created", func() {
+			BeforeEach(func() { workers = 10 })
+			JustBeforeEach(func() {
+				// Here, we use the internal function, to retrieve the real reflector also in case no workers are set.
+				rfl = newReflector(reflectorName, NewFakeNamespacedReflector, NewFakeFallbackReflector, workers)
+			})
 			It("should return a non nil reflector", func() { Expect(rfl).ToNot(BeNil()) })
 			It("should correctly populate the reflector fields", func() {
 				Expect(rfl.(*reflector).name).To(BeIdenticalTo(reflectorName))