Fix manager crashloopback for ARC deployments without scaleset-related controllers (#2293)

main.go

@@ -317,7 +317,17 @@ func main() {
 		}
 	}
 
+	// We use this environment avariable to turn on the ScaleSet related controllers.
+	// Otherwise ARC's legacy chart is unable to deploy a working ARC controller-manager pod,
+	// due to that the chart does not contain new actions.* CRDs while ARC requires those CRDs.
+	//
+	// We might have used a more explicitly named environment variable for this,
+	// e.g. "CONTROLLER_MANAGER_ENABLE_SCALE_SET" to explicitly enable the new controllers,
+	// or "CONTROLLER_MANAGER_DISABLE_SCALE_SET" to explicitly disable the new controllers.
+	// However, doing so would affect either private ARC testers or current ARC users
+	// who run ARC without those variabls.
 	mgrPodName := os.Getenv("CONTROLLER_MANAGER_POD_NAME")
+	if mgrPodName != "" {
 		mgrPodNamespace := os.Getenv("CONTROLLER_MANAGER_POD_NAMESPACE")
 		var mgrPod corev1.Pod
 		err = mgr.GetAPIReader().Get(context.Background(), types.NamespacedName{Namespace: mgrPodNamespace, Name: mgrPodName}, &mgrPod)
@@ -340,7 +350,6 @@ func main() {
 			log.Error(err, "unable to obtain manager container image")
 			os.Exit(1)
 		}
-
 		if err = (&actionsgithubcom.AutoscalingRunnerSetReconciler{
 			Client:                             mgr.GetClient(),
 			Log:                                log.WithName("AutoscalingRunnerSet"),
@@ -382,6 +391,7 @@ func main() {
 			os.Exit(1)
 		}
 		// +kubebuilder:scaffold:builder
+	}
 
 	if !disableAdmissionWebhook && !autoScalingRunnerSetOnly {
 		injector := &actionssummerwindnet.PodRunnerTokenInjector{