feat: create client from kubeconfig if flag is set

Signed-off-by: Carlos Salas <carlos.salas@suse.com>

main.go

@@ -28,6 +28,9 @@ import (
 	"k8s.io/apimachinery/pkg/runtime"
 	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
 	clientgoscheme "k8s.io/client-go/kubernetes/scheme"
+	"k8s.io/client-go/rest"
+	"k8s.io/client-go/tools/clientcmd"
+	clientcmdapi "k8s.io/client-go/tools/clientcmd/api"
 	"k8s.io/client-go/tools/leaderelection/resourcelock"
 	"k8s.io/component-base/version"
 	"k8s.io/klog/v2"
@@ -57,6 +60,7 @@ var (
 	syncPeriod                  time.Duration
 	healthAddr                  string
 	concurrencyNumber           int
+	rancherKubeconfig           string
 )
 
 func init() {
@@ -97,6 +101,9 @@ func initFlags(fs *pflag.FlagSet) {
 
 	fs.IntVar(&concurrencyNumber, "concurrency", 1,
 		"Number of resources to process simultaneously")
+
+	fs.StringVar(&rancherKubeconfig, "rancher-kubeconfig", "",
+		"Path to a kubeconfig file. Only required if out-of-cluster.")
 }
 
 func main() {
@@ -154,12 +161,48 @@ func setupChecks(mgr ctrl.Manager) {
 	}
 }
 
+// setupReconcilers can either create a client for an in-cluster installation (rancher and rancher-turtles in the same cluster)
+// or create a client for an out-of-cluster installation (rancher and rancher-turtles in different clusters).
 func setupReconcilers(ctx context.Context, mgr ctrl.Manager) {
+	var c client.Client
+
+	if len(rancherKubeconfig) > 0 {
+		setupLog.Info("out-of-cluster installation of rancher-turtles", "using kubeconfig from path", rancherKubeconfig)
+
+		restConfig, err := loadConfigWithContext("", &clientcmd.ClientConfigLoadingRules{ExplicitPath: rancherKubeconfig}, "")
+		if err != nil {
+			setupLog.Error(err, "unable to load kubeconfig from file")
+			os.Exit(1)
+		}
+
+		c, err = client.New(restConfig, client.Options{Scheme: mgr.GetClient().Scheme()})
+
+		if err != nil {
+			setupLog.Error(err, "failed to create client")
+			os.Exit(1)
+		}
+	} else {
+		setupLog.Info("in-cluster installation of rancher-turtles")
+		c = mgr.GetClient()
+	}
+
 	if err := (&controllers.CAPIImportReconciler{
-		Client:           mgr.GetClient(),
+		Client:           c,
 		WatchFilterValue: watchFilterValue,
 	}).SetupWithManager(ctx, mgr, controller.Options{MaxConcurrentReconciles: concurrencyNumber}); err != nil {
 		setupLog.Error(err, "unable to create capi controller")
 		os.Exit(1)
 	}
 }
+
+// loadConfigWithContext loads a REST Config from a path using a logic similar to the one used in controller-runtime.
+func loadConfigWithContext(apiServerURL string, loader clientcmd.ClientConfigLoader, context string) (*rest.Config, error) {
+	return clientcmd.NewNonInteractiveDeferredLoadingClientConfig(
+		loader,
+		&clientcmd.ConfigOverrides{
+			ClusterInfo: clientcmdapi.Cluster{
+				Server: apiServerURL,
+			},
+			CurrentContext: context,
+		}).ClientConfig()
+}