fix: prevent HTTP and metrics ports from being the same (#482)

Author: kimdre

cmd/doco-cd/main.go

@@ -316,7 +316,7 @@ func main() {
 		log.Info("serving prometheus metrics", slog.Int("http_port", int(c.MetricsPort)), slog.String("path", prometheus.MetricsPath))
 
 		if err = prometheus.Serve(c.MetricsPort); err != nil {
-			log.Error("failed to start Prometheus metrics server", logger.ErrAttr(err))
+			log.Critical("failed to start Prometheus metrics server", logger.ErrAttr(err))
 		} else {
 			log.Debug("Prometheus metrics server started successfully", slog.Int("port", int(c.MetricsPort)))
 		}

internal/config/app_config.go

@@ -67,6 +67,10 @@ func GetAppConfig() (*AppConfig, error) {
 		return nil, err
 	}
 
+	if cfg.HttpPort == cfg.MetricsPort {
+		return nil, fmt.Errorf("HTTP_PORT and METRICS_PORT cannot be the same port number: %d", cfg.HttpPort)
+	}
+
 	if cfg.HttpProxyString != "" {
 		cfg.HttpProxy = transport.ProxyOptions{
 			URL: cfg.HttpProxyString,