fix: metric module init exactly once when there is multiple service o…

…r reference

metrics/api.go

@@ -17,6 +17,10 @@
 
 package metrics
 
+import (
+	"sync"
+)
+
 import (
 	"dubbo.apache.org/dubbo-go/v3/common"
 	"dubbo.apache.org/dubbo-go/v3/common/constant"
@@ -26,23 +30,26 @@ var (
 	registries = make(map[string]func(*common.URL) MetricRegistry)
 	collectors = make([]CollectorFunc, 0)
 	registry   MetricRegistry
+	once       sync.Once
 )
 
 // CollectorFunc used to extend more indicators
 type CollectorFunc func(MetricRegistry, *common.URL)
 
 // Init Metrics module
 func Init(url *common.URL) {
-	InitAppInfo(url.GetParam(constant.ApplicationKey, ""), url.GetParam(constant.AppVersionKey, ""))
-	// defalut protocol is already set in metricConfig
-	regFunc, ok := registries[url.Protocol]
-	if ok {
-		registry = regFunc(url)
-		for _, co := range collectors {
-			co(registry, url)
+	once.Do(func() {
+		InitAppInfo(url.GetParam(constant.ApplicationKey, ""), url.GetParam(constant.AppVersionKey, ""))
+		// defalut protocol is already set in metricConfig
+		regFunc, ok := registries[url.Protocol]
+		if ok {
+			registry = regFunc(url)
+			for _, co := range collectors {
+				co(registry, url)
+			}
+			registry.Export()
 		}
-		registry.Export()
-	}
+	})
 }
 
 // SetRegistry extend more MetricRegistry, default PrometheusRegistry