Api metrics (#1014)

* api metrics support

* comments reflected

* metrics middleware fix

api/server/gin_middlewares.go

@@ -14,8 +14,11 @@ import (
 	"github.com/gin-contrib/cors"
 	"github.com/gin-gonic/gin"
 	"github.com/sirupsen/logrus"
+	"go.opencensus.io/stats"
 	"go.opencensus.io/tag"
 	"go.opencensus.io/trace"
+	"strconv"
+	"time"
 )
 
 func optionalCorsWrap(r *gin.Engine) {
@@ -75,6 +78,54 @@ func traceWrap(c *gin.Context) {
 	c.Next()
 }
 
+func apiMetricsWrap(s *Server) {
+
+	measure := func(engine *gin.Engine) func(*gin.Context) {
+		var routes gin.RoutesInfo
+		return func(c *gin.Context) {
+			if routes == nil {
+				routes = engine.Routes()
+			}
+			start := time.Now()
+			// get the handler url, example: /v1/apps/:app
+			url := ""
+			for _, r := range routes {
+				if r.Handler == c.HandlerName() {
+					url = r.Path
+					break
+				}
+			}
+
+			ctx, err := tag.New(c.Request.Context(),
+				tag.Upsert(pathKey, url),
+				tag.Upsert(methodKey, c.Request.Method),
+			)
+			if err != nil {
+				logrus.Fatal(err)
+			}
+			stats.Record(ctx, apiRequestCount.M(1))
+			c.Next()
+
+			status := strconv.Itoa(c.Writer.Status())
+			ctx, err = tag.New(ctx,
+				tag.Upsert(statusKey, status),
+			)
+			if err != nil {
+				logrus.Fatal(err)
+			}
+			stats.Record(ctx, apiLatency.M(float64(time.Since(start))/float64(time.Millisecond)))
+		}
+	}
+
+	r := s.Router
+	r.Use(measure(r))
+	if s.webListenPort != s.adminListenPort {
+		a := s.AdminRouter
+		a.Use(measure(a))
+	}
+
+}
+
 func panicWrap(c *gin.Context) {
 	defer func(c *gin.Context) {
 		if rec := recover(); rec != nil {