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 {

api/server/server.go

@@ -537,6 +537,7 @@ func New(ctx context.Context, opts ...ServerOption) *Server {
 	setMachineID()
 	s.Router.Use(loggerWrap, traceWrap, panicWrap) // TODO should be opts
 	optionalCorsWrap(s.Router)                     // TODO should be an opt
+	apiMetricsWrap(s)
 	s.bindHandlers(ctx)
 
 	s.appListeners = new(appListeners)
@@ -572,6 +573,7 @@ func WithPrometheus() ServerOption {
 		}
 		s.promExporter = exporter
 		view.RegisterExporter(exporter)
+		registerViews()
 		return nil
 	}
 }

api/server/stats.go

@@ -0,0 +1,68 @@
+package server
+
+import (
+	"github.com/sirupsen/logrus"
+	"go.opencensus.io/stats"
+	"go.opencensus.io/stats/view"
+	"go.opencensus.io/tag"
+)
+
+var (
+	apiRequestCount = stats.Int64("api/request_count", "Number of API requests", stats.UnitDimensionless)
+	apiLatency      = stats.Float64("api/latency", "API latency", stats.UnitMilliseconds)
+)
+
+var (
+	pathKey   = makeKey("path")
+	methodKey = makeKey("method")
+	statusKey = makeKey("status")
+)
+
+var (
+	defaultLatencyDistribution = view.Distribution(0, 1, 2, 3, 4, 5, 6, 8, 10, 13, 16, 20, 25, 30, 40, 50, 65, 80, 100, 130, 160, 200, 250, 300, 400, 500, 650, 800, 1000, 2000, 5000, 10000, 20000, 50000, 100000)
+)
+
+var (
+	ApiRequestCountView = &view.View{
+		Name:        "api/request_count",
+		Description: "Count of API requests started",
+		Measure:     apiRequestCount,
+		TagKeys:     []tag.Key{pathKey, methodKey},
+		Aggregation: view.Count(),
+	}
+
+	ApiResponseCountView = &view.View{
+		Name:        "api/response_count",
+		Description: "API response count",
+		TagKeys:     []tag.Key{pathKey, methodKey, statusKey},
+		Measure:     apiLatency,
+		Aggregation: view.Count(),
+	}
+
+	ApiLatencyView = &view.View{
+		Name:        "api/latency",
+		Description: "Latency distribution of API requests",
+		Measure:     apiLatency,
+		TagKeys:     []tag.Key{pathKey, methodKey, statusKey},
+		Aggregation: defaultLatencyDistribution,
+	}
+)
+
+func registerViews() {
+	err := view.Register(
+		ApiRequestCountView,
+		ApiResponseCountView,
+		ApiLatencyView,
+	)
+	if err != nil {
+		logrus.WithError(err).Fatal("cannot register view")
+	}
+}
+
+func makeKey(name string) tag.Key {
+	key, err := tag.NewKey(name)
+	if err != nil {
+		logrus.Fatal(err)
+	}
+	return key
+}