introduce a new runnable group for basic servers of the manager

pkg/manager/internal.go

@@ -459,7 +459,17 @@ func (cm *controllerManager) Start(ctx context.Context) (err error) {
 		}
 	}
 
-	// First start any webhook servers, which includes conversion, validation, and defaulting
+	// First start any basic servers, which includes health probes, metrics and profiling if enabled.
+	//
+	// WARNING: Basic servers MUST start before any cache is populated, otherwise it would block
+	// conversion webhooks to be ready for serving which make the cache never get ready.
+	if err := cm.runnables.BasicServers.Start(cm.internalCtx); err != nil {
+		if err != nil {
+			return fmt.Errorf("failed to start basic servers: %w", err)
+		}
+	}
+
+	// Start any webhook servers, which includes conversion, validation, and defaulting
 	// webhooks that are registered.
 	//
 	// WARNING: Webhooks MUST start before any cache is populated, otherwise there is a race condition
@@ -591,10 +601,13 @@ func (cm *controllerManager) engageStopProcedure(stopComplete <-chan struct{}) e
 		cm.logger.Info("Stopping and waiting for caches")
 		cm.runnables.Caches.StopAndWait(cm.shutdownCtx)
 
-		// Webhooks should come last, as they might be still serving some requests.
+		// Webhooks and basic servers should come last, as they might be still serving some requests.
 		cm.logger.Info("Stopping and waiting for webhooks")
 		cm.runnables.Webhooks.StopAndWait(cm.shutdownCtx)
 
+		cm.logger.Info("Stopping and waiting for basic servers")
+		cm.runnables.BasicServers.StopAndWait(cm.shutdownCtx)
+
 		// Proceed to close the manager and overall shutdown context.
 		cm.logger.Info("Wait completed, proceeding to shutdown the manager")
 		shutdownCancel()

pkg/manager/runnable_group.go

@@ -28,6 +28,7 @@ type runnableCheck func(ctx context.Context) bool
 // runnables handles all the runnables for a manager by grouping them accordingly to their
 // type (webhooks, caches etc.).
 type runnables struct {
+	BasicServers   *runnableGroup
 	Webhooks       *runnableGroup
 	Caches         *runnableGroup
 	LeaderElection *runnableGroup
@@ -37,6 +38,7 @@ type runnables struct {
 // newRunnables creates a new runnables object.
 func newRunnables(baseContext BaseContextFunc, errChan chan error) *runnables {
 	return &runnables{
+		BasicServers:   newRunnableGroup(baseContext, errChan),
 		Webhooks:       newRunnableGroup(baseContext, errChan),
 		Caches:         newRunnableGroup(baseContext, errChan),
 		LeaderElection: newRunnableGroup(baseContext, errChan),
@@ -52,6 +54,8 @@ func newRunnables(baseContext BaseContextFunc, errChan chan error) *runnables {
 // The runnables added after Start are started directly.
 func (r *runnables) Add(fn Runnable) error {
 	switch runnable := fn.(type) {
+	case *server:
+		return r.BasicServers.Add(fn, nil)
 	case hasCache:
 		return r.Caches.Add(fn, func(ctx context.Context) bool {
 			return runnable.GetCache().WaitForCacheSync(ctx)

pkg/manager/runnable_group_test.go

@@ -21,6 +21,13 @@ var _ = Describe("runnables", func() {
 		Expect(newRunnables(defaultBaseContext, errCh)).ToNot(BeNil())
 	})
 
+	It("should add basic servers to the appropriate group", func() {
+		server := &server{}
+		r := newRunnables(defaultBaseContext, errCh)
+		Expect(r.Add(server)).To(Succeed())
+		Expect(r.BasicServers.startQueue).To(HaveLen(1))
+	})
+
 	It("should add caches to the appropriate group", func() {
 		cache := &cacheProvider{cache: &informertest.FakeInformers{Error: fmt.Errorf("expected error")}}
 		r := newRunnables(defaultBaseContext, errCh)