add legacy CLI option

Signed-off-by: Seán C McCord <ulexus@gmail.com>

cmd/dispatchers/main.go

@@ -26,6 +26,7 @@ var rpcHost string
 var kubeCfg string
 
 var apiAddr string
+var legacyEndpointSlices bool
 
 // KamailioStartupDebounceTimer is the amount of time to wait on startup to
 // send an additional notify to kamailio.
@@ -46,6 +47,7 @@ func init() {
 	flag.StringVar(&rpcPort, "p", "9998", "Port for kamailio's RPC service")
 	flag.StringVar(&kubeCfg, "kubecfg", "", "Location of kubecfg file (if not running inside k8s)")
 	flag.StringVar(&apiAddr, "api", "", "Address on which to run web API service.  Example ':8080'. (defaults to not run)")
+	flag.BoolVar(&legacyEndpointSlices, "legacy-endpointslices", false, "Use legacy v1beta1 EndpointSlices, for Kubernetes earlier than v1.21")
 }
 
 func main() {
@@ -97,7 +99,13 @@ func run() (err error) {
 	informerFactory := informers.NewSharedInformerFactory(kc, 10*time.Minute)
 
 	for _, v := range setDefinitions.list {
-		ds, err := sets.NewKubernetesSet(ctx, informerFactory, v.id, v.namespace, v.name, v.port)
+		var ds sets.DispatcherSet
+
+		if legacyEndpointSlices {
+			ds, err = sets.NewLegacyKubernetesSet(ctx, informerFactory, v.id, v.namespace, v.name, v.port)
+		} else {
+			ds, err = sets.NewKubernetesSet(ctx, informerFactory, v.id, v.namespace, v.name, v.port)
+		}
 		if err != nil {
 			return fmt.Errorf("failed to create dispatcher set %s: %w", v.String(), err)
 		}