Make the external url of cache server configurable if necessary

pkg/artifactcache/handler.go

@@ -38,10 +38,11 @@ type Handler struct {
 	gcing atomic.Bool
 	gcAt  time.Time
 
-	outboundIP string
+	outboundIP   string
+	advertiseURL string
 }
 
-func StartHandler(dir, outboundIP string, port uint16, logger logrus.FieldLogger) (*Handler, error) {
+func StartHandler(dir, advertiseURL, outboundIP string, port uint16, logger logrus.FieldLogger) (*Handler, error) {
 	h := &Handler{}
 
 	if logger == nil {
@@ -71,6 +72,8 @@ func StartHandler(dir, outboundIP string, port uint16, logger logrus.FieldLogger
 	}
 	h.storage = storage
 
+	h.advertiseURL = advertiseURL
+
 	if outboundIP != "" {
 		h.outboundIP = outboundIP
 	} else if ip := common.GetOutboundIP(); ip == nil {
@@ -111,10 +114,13 @@ func StartHandler(dir, outboundIP string, port uint16, logger logrus.FieldLogger
 }
 
 func (h *Handler) ExternalURL() string {
-	// TODO: make the external url configurable if necessary
-	return fmt.Sprintf("http://%s:%d",
-		h.outboundIP,
-		h.listener.Addr().(*net.TCPAddr).Port)
+	if h.advertiseURL != "" {
+		return h.advertiseURL
+	} else {
+		return fmt.Sprintf("http://%s:%d",
+			h.outboundIP,
+			h.listener.Addr().(*net.TCPAddr).Port)
+	}
 }
 
 func (h *Handler) Close() error {