feat(dns): allow setting an externally managed cluster domain

cmd/uc/dns/set.go

@@ -8,6 +8,7 @@ import (
 	"github.com/miekg/dns"
 	"github.com/psviderski/uncloud/api/pb"
 	"github.com/psviderski/uncloud/internal/cli"
+	"github.com/psviderski/uncloud/internal/cli/tui"
 	"github.com/spf13/cobra"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
@@ -17,9 +18,14 @@ func NewSetCommand() *cobra.Command {
 	cmd := &cobra.Command{
 		Use:   "set DOMAIN_NAME",
 		Args:  cobra.ExactArgs(1),
-		Short: "Set a cluster domain directly in the cluster.",
-		Long: "Set a cluster domain directly in the cluster, bypassing Uncloud DNS. " +
-			"This assumes the DNS is externally set up.",
+		Short: "Set or unset an externally managed cluster domain (EXPERIMENTAL).",
+		Long: "EXPERIMENTAL: Set the cluster domain used to generate ingress hostnames for services.\n" +
+			"Configure wildcard DNS records for this domain with your DNS provider. " +
+			"Uncloud will not create, verify, update, or delete external DNS records.\n" +
+			"Pass an empty string to unset a manually set domain. " +
+			"Use 'uc dns release' to release a domain reserved in Uncloud DNS. " +
+			"Setting or unsetting the domain does not change existing service hostnames.",
+		Example: "  uc dns set apps.example.com\n  uc dns set \"\"",
 		RunE: func(cmd *cobra.Command, args []string) error {
 			uncli := cmd.Context().Value("cli").(*cli.CLI)
 			return set(cmd.Context(), uncli, args[0])
@@ -30,10 +36,12 @@ func NewSetCommand() *cobra.Command {
 }
 
 func set(ctx context.Context, uncli *cli.CLI, name string) error {
-	labels, ok := dns.IsDomainName(name)
-	if !ok || labels < 3 {
-		return fmt.Errorf("domain '%s' is not a valid name", name)
+	if name != "" {
+		if labels, ok := dns.IsDomainName(name); !ok || labels < 2 {
+			return fmt.Errorf("invalid cluster domain %q: must be a valid domain name with at least two labels", name)
+		}
 	}
+	tui.PrintWarning("Setting an externally managed cluster domain is experimental.")
 
 	clusterClient, err := uncli.ConnectCluster(ctx)
 	if err != nil {
@@ -41,17 +49,21 @@ func set(ctx context.Context, uncli *cli.CLI, name string) error {
 	}
 	defer clusterClient.Close()
 
-	domain, err := clusterClient.SetDomain(ctx, &pb.SetDomainRequest{Name: name})
+	_, err = clusterClient.SetDomain(ctx, &pb.SetDomainRequest{Name: name})
 	if err != nil {
 		if status.Convert(err).Code() == codes.AlreadyExists {
-			return errors.New("domain already reserved")
+			return errors.New("cluster domain already configured, unset it with 'uc dns set \"\"' or " +
+				"release a reservation with 'uc dns release' first")
 		}
-		return err
+		return fmt.Errorf("set cluster domain: %w", err)
 	}
 
-	fmt.Printf("Set cluster domain: %s\n", domain.Name)
-
-	// No need to update anything as the domain records pointing to this cluster should be wildcard, so all
-	// names already exist.
+	if name == "" {
+		fmt.Println("Unset cluster domain. External DNS records have not been changed.")
+		return nil
+	}
+	fmt.Printf("Set cluster domain: %s\n", name)
+	fmt.Println("DNS is managed externally. " +
+		"Configure wildcard DNS records pointing to machines running the Caddy service.")
 	return nil
 }