fix when to invoke NewPrometheusMiddleware twice lead a panic

prometheusmiddleware.go

@@ -13,6 +13,7 @@ import (
 )
 
 var (
+	isRegistered = false // fix when to invoke NewPrometheusMiddleware twice lead a panic: duplicate metrics collector registration attempted
 	promLabelNames = []string{"code", "method", "path"}
 	requestCounter = prometheus.NewCounterVec(
 		prometheus.CounterOpts(prometheus.Opts{
@@ -29,13 +30,16 @@ var (
 // The prometheus is a monitoring system and time series database.
 // Note: the returned middleware contains the function of logmiddleware.
 func NewPrometheusMiddleware(bindAddr string, xRealIp bool, logger *zap.Logger) Middleware {
-	go func() {
-		prometheus.MustRegister(requestCounter)
-		prometheus.MustRegister(responseTimeSummary)
-		http.Handle("/metrics", promhttp.Handler())
-		logger.Debug("prometheus metrics server start at " + bindAddr)
-		http.ListenAndServe(bindAddr, nil)
-	}()
+	if !isRegistered {
+		go func() {
+			prometheus.MustRegister(requestCounter)
+			prometheus.MustRegister(responseTimeSummary)
+			isRegistered = true
+			http.Handle("/metrics", promhttp.Handler())
+			logger.Debug("prometheus metrics server start at " + bindAddr)
+			http.ListenAndServe(bindAddr, nil)
+		}()
+	}
 	return func(h fasthttp.RequestHandler) fasthttp.RequestHandler {
 		return func(ctx *fasthttp.RequestCtx) {
 			startTime := time.Now()
@@ -50,7 +54,7 @@ func NewPrometheusMiddleware(bindAddr string, xRealIp bool, logger *zap.Logger)
 			responseTime := time.Since(startTime).Seconds() * 1000
 			responseTimeSummary.With(promLabels).Observe(responseTime)
 			requestCounter.With(promLabels).Inc()
-			if ctx.Response.StatusCode()/100 == 2 {
+			if ctx.Response.StatusCode() / 100 == 2 {
 				logger.Info("access", zap.Int("code", ctx.Response.StatusCode()), zap.Float64("time", responseTime), zap.String("method", promLabels["method"]), zap.String("path", promLabels["path"]), addrField)
 			} else {
 				logger.Warn("access", zap.Int("code", ctx.Response.StatusCode()), zap.Float64("time", responseTime), zap.String("method", promLabels["method"]), zap.String("path", promLabels["path"]), addrField)