Refactor Prometheus metrics configuration and validation

Author: axllent

cmd/root.go

@@ -121,8 +121,8 @@ func init() {
 	rootCmd.Flags().StringVar(&config.SendAPIAuthFile, "send-api-auth-file", config.SendAPIAuthFile, "A password file for Send API authentication")
 	rootCmd.Flags().BoolVar(&config.SendAPIAuthAcceptAny, "send-api-auth-accept-any", config.SendAPIAuthAcceptAny, "Accept any username and password for the Send API endpoint, including none")
 
-	// Prometheus Metrics
-	rootCmd.Flags().StringVar(&config.PrometheusListen, "enable-prometheus", config.PrometheusListen, "Enable Prometheus metrics: false=disabled, 'true'=use web port, address=separate server (':9090')")
+	// Prometheus metrics
+	rootCmd.Flags().StringVar(&config.PrometheusListen, "enable-prometheus", config.PrometheusListen, "Enable Prometheus metrics: true|false|<bind interface & port> (eg:':9090')")
 
 	// SMTP server
 	rootCmd.Flags().StringVarP(&config.SMTPListen, "smtp", "s", config.SMTPListen, "SMTP bind interface and port")

config/config.go

@@ -192,7 +192,7 @@ var (
 	AllowUntrustedTLS bool
 
 	// PrometheusListen address for Prometheus metrics server
-	// Empty = disabled, "true"= use existing web server, address = separate server
+	// Empty = disabled, true= use existing web server, address = separate server
 	PrometheusListen string
 
 	// Version is the default application version, updated on release
@@ -362,6 +362,20 @@ func VerifyConfig() error {
 		logger.Log().Info("[send-api] disabling authentication")
 	}
 
+	// Prometheus configuration validation
+	if PrometheusListen != "" {
+		mode := strings.ToLower(strings.TrimSpace(PrometheusListen))
+		if mode != "true" && mode != "false" {
+			// Validate as address for separate server mode
+			_, err := net.ResolveTCPAddr("tcp", PrometheusListen)
+			if err != nil {
+				return fmt.Errorf("[prometheus] %s", err.Error())
+			}
+		} else if mode == "true" {
+			logger.Log().Info("[prometheus] enabling metrics")
+		}
+	}
+
 	// SMTP server
 	if SMTPTLSCert != "" && SMTPTLSKey == "" || SMTPTLSCert == "" && SMTPTLSKey != "" {
 		return errors.New("[smtp] you must provide both an SMTP TLS certificate and a key")
@@ -571,17 +585,5 @@ func VerifyConfig() error {
 		logger.Log().Info("demo mode enabled")
 	}
 
-	// Prometheus configuration validation
-	if PrometheusListen != "" {
-		mode := strings.ToLower(strings.TrimSpace(PrometheusListen))
-		if mode != "true" && mode != "false" {
-			// Validate as address for separate server mode
-			_, err := net.ResolveTCPAddr("tcp", PrometheusListen)
-			if err != nil {
-				return fmt.Errorf("[prometheus] %s", err.Error())
-			}
-		}
-	}
-
 	return nil
 }