Add --namespace flag to watch only specific namespace if necessary.

Author: Gerrit91

cmd/main.go

@@ -31,6 +31,7 @@ import (
 	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
 	clientgoscheme "k8s.io/client-go/kubernetes/scheme"
 	ctrl "sigs.k8s.io/controller-runtime"
+	"sigs.k8s.io/controller-runtime/pkg/cache"
 	"sigs.k8s.io/controller-runtime/pkg/healthz"
 	"sigs.k8s.io/controller-runtime/pkg/log/zap"
 	"sigs.k8s.io/controller-runtime/pkg/metrics/filters"
@@ -59,15 +60,20 @@ func init() {
 }
 
 func main() {
-	var metricsAddr string
-	var enableLeaderElection bool
-	var probeAddr string
-	var secureMetrics bool
-	var enableHTTP2 bool
-	var tlsOpts []func(*tls.Config)
+	var (
+		metricsAddr          string
+		enableLeaderElection bool
+		probeAddr            string
+		namespace            string
+		secureMetrics        bool
+		enableHTTP2          bool
+		tlsOpts              []func(*tls.Config)
+	)
+
 	flag.StringVar(&metricsAddr, "metrics-bind-address", "0", "The address the metrics endpoint binds to. "+
 		"Use :8443 for HTTPS or :8080 for HTTP, or leave as 0 to disable the metrics service.")
 	flag.StringVar(&probeAddr, "health-probe-bind-address", ":8081", "The address the probe endpoint binds to.")
+	flag.StringVar(&namespace, "namespace", "", "The namespace to watch for resources to reconcile. If not specified, watches all namespaces.")
 	flag.BoolVar(&enableLeaderElection, "leader-elect", false,
 		"Enable leader election for controller manager. "+
 			"Enabling this will ensure there is only one active controller manager.")
@@ -133,13 +139,23 @@ func main() {
 		metricsServerOptions.FilterProvider = filters.WithAuthenticationAndAuthorization
 	}
 
+	var mgrOpts cache.Options
+	if namespace != "" {
+		mgrOpts = cache.Options{
+			DefaultNamespaces: map[string]cache.Config{
+				namespace: {},
+			},
+		}
+	}
+
 	mgr, err := ctrl.NewManager(ctrl.GetConfigOrDie(), ctrl.Options{
 		Scheme:                 scheme,
 		Metrics:                metricsServerOptions,
 		WebhookServer:          webhookServer,
 		HealthProbeBindAddress: probeAddr,
 		LeaderElection:         enableLeaderElection,
 		LeaderElectionID:       "6fca141d.cluster.x-k8s.io",
+		Cache:                  mgrOpts,
 		// LeaderElectionReleaseOnCancel defines if the leader should step down voluntarily
 		// when the Manager ends. This requires the binary to immediately end when the
 		// Manager is stopped, otherwise, this setting is unsafe. Setting this significantly