chore: refactor Caddyfile generator to accept a validator

internal/machine/caddyconfig/caddyfile.go

@@ -45,7 +45,43 @@ https://{{$hostname}} {
 }{{end}}
 `
 
-func GenerateCaddyfile(containers []api.ServiceContainer, verifyResponse string) (string, error) {
+// CaddyfileGenerator generates a Caddyfile configuration for the Caddy reverse proxy.
+type CaddyfileGenerator struct {
+	// MachineID is the unique identifier of the machine where the controller is running.
+	MachineID string
+	Validator CaddyfileValidator
+}
+
+// CaddyfileValidator is an interface for validating Caddyfile configurations.
+type CaddyfileValidator interface {
+	Validate(caddyfile string) error
+}
+
+// Generate creates a Caddyfile configuration based on the provided service containers.
+// If a 'caddy' service container is running on this machine and defines a custom Caddy config (x-caddy) in its service
+// spec, it will be validated and prepended to the generated Caddyfile. Custom Caddy configs (x-caddy) defined in other
+// service specs are validated and appended to the generated Caddyfile. Invalid configs are logged and skipped to ensure
+// the generated Caddyfile remains valid.
+//
+// The final Caddyfile structure includes:
+//
+//	[caddy x-caddy]
+//	[generated Caddyfile from all service ports]
+//	[service-a x-caddy]
+//	...
+//	[service-z x-caddy]
+func (g *CaddyfileGenerator) Generate(containers []api.ServiceContainer) (string, error) {
+	baseCaddyfile, err := g.generateBaseFromPorts(containers)
+	if err != nil {
+		return "", fmt.Errorf("generate base Caddyfile from service ports: %w", err)
+	}
+
+	// TODO: Implement support for custom Caddy configs (x-caddy) in service specs.
+
+	return baseCaddyfile, nil
+}
+
+func (g *CaddyfileGenerator) generateBaseFromPorts(containers []api.ServiceContainer) (string, error) {
 	httpHostUpstreams, httpsHostUpstreams := httpUpstreamsFromContainers(containers)
 
 	funcs := template.FuncMap{"join": strings.Join}
@@ -61,7 +97,7 @@ func GenerateCaddyfile(containers []api.ServiceContainer, verifyResponse string)
 		HTTPSHostUpstreams map[string][]string
 	}{
 		VerifyPath:         VerifyPath,
-		VerifyResponse:     verifyResponse,
+		VerifyResponse:     g.MachineID,
 		HTTPHostUpstreams:  httpHostUpstreams,
 		HTTPSHostUpstreams: httpsHostUpstreams,
 	}

internal/machine/caddyconfig/caddyfile_test.go

@@ -8,10 +8,10 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-func TestGenerateCaddyfile(t *testing.T) {
+func TestCaddyfileGenerator(t *testing.T) {
 	caddyfileHeader := `http:// {
 	handle /.uncloud-verify {
-		respond "verification-response-body" 200
+		respond "test-machine-id" 200
 	}
 	log
 }
@@ -24,6 +24,10 @@ func TestGenerateCaddyfile(t *testing.T) {
 }
 `
 
+	generator := &CaddyfileGenerator{
+		MachineID: "test-machine-id",
+	}
+
 	tests := []struct {
 		name       string
 		containers []api.ServiceContainer
@@ -182,7 +186,7 @@ http://app.example.com {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			config, err := GenerateCaddyfile(tt.containers, "verification-response-body")
+			config, err := generator.Generate(tt.containers)
 
 			if tt.wantErr {
 				assert.Error(t, err)

internal/machine/caddyconfig/controller.go

@@ -22,13 +22,14 @@ const (
 // proxy. The generated configuration allows Caddy to route external traffic to service containers across the internal
 // network.
 type Controller struct {
-	store          *store.Store
+	machineID string
 	configDir string
-	verifyResponse string
+	generator *CaddyfileGenerator
+	store     *store.Store
 	log       *slog.Logger
 }
 
-func NewController(store *store.Store, configDir string, verifyResponse string) (*Controller, error) {
+func NewController(machineID, configDir, adminSock string, store *store.Store) (*Controller, error) {
 	if err := os.MkdirAll(configDir, 0o750); err != nil {
 		return nil, fmt.Errorf("create directory for Caddy configuration '%s': %w", configDir, err)
 	}
@@ -36,10 +37,15 @@ func NewController(store *store.Store, configDir string, verifyResponse string)
 		return nil, fmt.Errorf("change owner of directory for Caddy configuration '%s': %w", configDir, err)
 	}
 
+	generator := &CaddyfileGenerator{
+		MachineID: machineID,
+	}
+
 	return &Controller{
-		store:          store,
+		machineID: machineID,
 		configDir: configDir,
-		verifyResponse: verifyResponse,
+		generator: generator,
+		store:     store,
 		log:       slog.With("component", "caddy-controller"),
 	}, nil
 }
@@ -73,20 +79,20 @@ func (c *Controller) Run(ctx context.Context) error {
 
 			containerRecords, err = c.store.ListContainers(ctx, store.ListOptions{})
 			if err != nil {
-				c.log.Info("Failed to list containers.", "err", err)
+				c.log.Error("Failed to list containers.", "err", err)
 				continue
 			}
 			containers, err = c.filterAvailableContainers(containerRecords)
 			if err != nil {
-				c.log.Info("Failed to filter available containers.", "err", err)
+				c.log.Error("Failed to filter available containers.", "err", err)
 				continue
 			}
 
 			if err = c.generateCaddyfile(containers); err != nil {
-				c.log.Info("Failed to generate Caddyfile configuration.", "err", err)
+				c.log.Error("Failed to generate Caddyfile configuration.", "err", err)
 			}
 			if err = c.generateJSONConfig(containers); err != nil {
-				c.log.Info("Failed to generate Caddy JSON configuration.", "err", err)
+				c.log.Error("Failed to generate Caddy JSON configuration.", "err", err)
 			}
 
 			c.log.Info("Updated Caddy configuration.", "dir", c.configDir)
@@ -110,12 +116,13 @@ func (c *Controller) filterAvailableContainers(
 }
 
 func (c *Controller) generateCaddyfile(containers []api.ServiceContainer) error {
-	caddyfile, err := GenerateCaddyfile(containers, c.verifyResponse)
+	caddyfile, err := c.generator.Generate(containers)
 	if err != nil {
 		return fmt.Errorf("generate Caddyfile: %w", err)
 	}
 	caddyfilePath := filepath.Join(c.configDir, "Caddyfile")
 
+	// TODO: use atomic file write to avoid partial loads on Caddy watch reload.
 	if err = os.WriteFile(caddyfilePath, []byte(caddyfile), 0o640); err != nil {
 		return fmt.Errorf("write Caddyfile to file '%s': %w", caddyfilePath, err)
 	}
@@ -127,7 +134,7 @@ func (c *Controller) generateCaddyfile(containers []api.ServiceContainer) error
 }
 
 func (c *Controller) generateJSONConfig(containers []api.ServiceContainer) error {
-	config, err := GenerateJSONConfig(containers, c.verifyResponse)
+	config, err := GenerateJSONConfig(containers, c.machineID)
 	if err != nil {
 		return err
 	}

internal/machine/machine.go

@@ -42,6 +42,9 @@ const (
 	DefaultMachineSockPath = "/run/uncloud/machine.sock"
 	DefaultUncloudSockPath = "/run/uncloud/uncloud.sock"
 	DefaultSockGroup       = "uncloud"
+	// DefaultCaddyAdminSockPath is the default path to the Caddy admin socket for validating the generated Caddy
+	// reverse proxy configuration.
+	DefaultCaddyAdminSockPath = "/run/uncloud/caddy/admin.sock"
 )
 
 type Config struct {
@@ -387,7 +390,12 @@ func (m *Machine) Run(ctx context.Context) error {
 
 			// Create a new caddyconfig controller for managing the Caddy reverse proxy configuration.
 			// It will also serve the current machine ID at /.uncloud-verify to verify Caddy reachability.
-			caddyconfigCtrl, err := caddyconfig.NewController(m.store, m.config.CaddyConfigDir, m.state.ID)
+			caddyconfigCtrl, err := caddyconfig.NewController(
+				m.state.ID,
+				m.config.CaddyConfigDir,
+				DefaultCaddyAdminSockPath,
+				m.store,
+			)
 			if err != nil {
 				return fmt.Errorf("create caddyconfig controller: %w", err)
 			}