Move webhook setup before manager start

According to
kubernetes-sigs/controller-runtime#1148,
there's a race condition between manager start and webhook register.
This commit moved webhook setup before manager start.

Tested on GKE cluster. The nil pointer error was not detected for 20
times.

incubator/hnc/cmd/manager/main.go

@@ -153,32 +153,9 @@ func main() {
 		os.Exit(1)
 	}
 
-	go startControllers(mgr, setupFinished)
-
-	setupLog.Info("Starting manager")
-	if err := mgr.Start(ctrl.SetupSignalHandler()); err != nil {
-		setupLog.Error(err, "problem running manager")
-		os.Exit(1)
-	}
-}
-
-func startControllers(mgr ctrl.Manager, setupFinished chan struct{}) {
-	setupLog.Info("Waiting for certificate generation to complete")
-	// Block until the setup finishes.
-	<-setupFinished
-
-	if testLog {
-		stats.StartLoggingActivity()
-	}
-
-	// Create all reconciling controllers
+	// Register webhooks before manager start to avoid potential race conditions.
+	// See https://github.com/kubernetes-sigs/controller-runtime/issues/1148.
 	f := forest.NewForest()
-	setupLog.Info("Creating controllers", "maxReconciles", maxReconciles)
-	removeOldCRDVersion := true
-	if err := reconcilers.Create(mgr, f, maxReconciles, removeOldCRDVersion); err != nil {
-		setupLog.Error(err, "cannot create controllers")
-		os.Exit(1)
-	}
 
 	// Create all validating admission controllers.
 	if !novalidation {
@@ -202,5 +179,31 @@ func startControllers(mgr ctrl.Manager, setupFinished chan struct{}) {
 		os.Exit(1)
 	}
 
+	go startControllers(mgr, f, setupFinished)
+
+	setupLog.Info("Starting manager")
+	if err := mgr.Start(ctrl.SetupSignalHandler()); err != nil {
+		setupLog.Error(err, "problem running manager")
+		os.Exit(1)
+	}
+}
+
+func startControllers(mgr ctrl.Manager, f *forest.Forest, setupFinished chan struct{}) {
+	setupLog.Info("Waiting for certificate generation to complete")
+	// Block until the setup finishes.
+	<-setupFinished
+
+	if testLog {
+		stats.StartLoggingActivity()
+	}
+
+	// Create all reconciling controllers
+	setupLog.Info("Creating controllers", "maxReconciles", maxReconciles)
+	removeOldCRDVersion := true
+	if err := reconcilers.Create(mgr, f, maxReconciles, removeOldCRDVersion); err != nil {
+		setupLog.Error(err, "cannot create controllers")
+		os.Exit(1)
+	}
+
 	setupLog.Info("All controllers started; setup complete")
 }