embed: warns about empty hosts in advertise urls

Signed-off-by: Gyu-Ho Lee <gyuhox@gmail.com>

embed/config.go

@@ -299,6 +299,14 @@ func (cfg *Config) Validate() error {
 	if err := checkBindURLs(cfg.ListenMetricsUrls); err != nil {
 		return err
 	}
+	if err := checkHostURLs(cfg.APUrls); err != nil {
+		// TODO: return err in v3.4
+		plog.Warningf("advertise-peer-urls %+v is deprecated (%v)", cfg.APUrls, err)
+	}
+	if err := checkHostURLs(cfg.ACUrls); err != nil {
+		// TODO: return err in v3.4
+		plog.Warningf("advertise-client-urls %+v is deprecated (%v)", cfg.ACUrls, err)
+	}
 
 	// Check if conflicting flags are passed.
 	nSet := 0
@@ -484,3 +492,16 @@ func checkBindURLs(urls []url.URL) error {
 	}
 	return nil
 }
+
+func checkHostURLs(urls []url.URL) error {
+	for _, url := range urls {
+		host, _, err := net.SplitHostPort(url.Host)
+		if err != nil {
+			return err
+		}
+		if host == "" {
+			return fmt.Errorf("unexpected empty host (%s)", url.String())
+		}
+	}
+	return nil
+}