fn: API stats and tags reoorganization (#1171)

Make sure we can apply extra tags if RegisterAPIViews() is
provided with such tags. Deduplicate path/method/status and
always apply these default tags to appropriate views.

api/common/stats_utils.go

@@ -8,11 +8,16 @@ import (
 )
 
 func CreateView(measure stats.Measure, agg *view.Aggregation, tagKeys []string) *view.View {
+	keys := makeKeys(tagKeys)
+	return CreateViewWithTags(measure, agg, keys)
+}
+
+func CreateViewWithTags(measure stats.Measure, agg *view.Aggregation, tags []tag.Key) *view.View {
 	return &view.View{
 		Name:        measure.Name(),
 		Description: measure.Description(),
 		Measure:     measure,
-		TagKeys:     makeKeys(tagKeys),
+		TagKeys:     tags,
 		Aggregation: agg,
 	}
 }
@@ -21,14 +26,18 @@ func MakeMeasure(name string, desc string, unit string) *stats.Int64Measure {
 	return stats.Int64(name, desc, unit)
 }
 
+func MakeKey(name string) tag.Key {
+	key, err := tag.NewKey(name)
+	if err != nil {
+		logrus.WithError(err).Fatalf("Cannot create tag %s", name)
+	}
+	return key
+}
+
 func makeKeys(names []string) []tag.Key {
 	tagKeys := make([]tag.Key, len(names))
 	for i, name := range names {
-		key, err := tag.NewKey(name)
+		tagKeys[i] = MakeKey(name)
-		if err != nil {
-			logrus.Fatal(err)
-		}
-		tagKeys[i] = key
 	}
 	return tagKeys
 }

api/server/gin_middlewares.go

@@ -15,12 +15,23 @@ import (
 	"github.com/gin-gonic/gin"
 	"github.com/sirupsen/logrus"
 	"go.opencensus.io/stats"
+	"go.opencensus.io/stats/view"
 	"go.opencensus.io/tag"
 	"go.opencensus.io/trace"
 	"strconv"
 	"time"
 )
 
+var (
+	pathKey   = common.MakeKey("path")
+	methodKey = common.MakeKey("method")
+	statusKey = common.MakeKey("status")
+
+	apiRequestCountMeasure  = common.MakeMeasure("api/request_count", "Count of API requests started", stats.UnitDimensionless)
+	apiResponseCountMeasure = common.MakeMeasure("api/response_count", "API response count", stats.UnitDimensionless)
+	apiLatencyMeasure       = common.MakeMeasure("api/latency", "Latency distribution of API requests", stats.UnitMilliseconds)
+)
+
 func optionalCorsWrap(r *gin.Engine) {
 	// By default no CORS are allowed unless one
 	// or more Origins are defined by the API_CORS
@@ -78,19 +89,31 @@ func traceWrap(c *gin.Context) {
 	c.Next()
 }
 
+func RegisterAPIViews(tagKeys []string, dist []float64) {
+
+	// default tags for request and response
+	reqTags := []tag.Key{pathKey, methodKey}
+	respTags := []tag.Key{pathKey, methodKey, statusKey}
+
+	// add extra tags if not already in default tags for req/resp
+	for _, key := range tagKeys {
+		if key != "path" && key != "method" && key != "status" {
+			reqTags = append(reqTags, common.MakeKey(key))
+			respTags = append(respTags, common.MakeKey(key))
+		}
+	}
+
+	err := view.Register(
+		common.CreateViewWithTags(apiRequestCountMeasure, view.Count(), reqTags),
+		common.CreateViewWithTags(apiResponseCountMeasure, view.Count(), respTags),
+		common.CreateViewWithTags(apiLatencyMeasure, view.Distribution(dist...), respTags),
+	)
+	if err != nil {
+		logrus.WithError(err).Fatal("cannot register view")
+	}
+}
+
 func apiMetricsWrap(s *Server) {
-	pathKey, err := tag.NewKey("path")
-	if err != nil {
-		logrus.Fatal(err)
-	}
-	methodKey, err := tag.NewKey("method")
-	if err != nil {
-		logrus.Fatal(err)
-	}
-	statusKey, err := tag.NewKey("status")
-	if err != nil {
-		logrus.Fatal(err)
-	}
 
 	measure := func(engine *gin.Engine) func(*gin.Context) {
 		var routes gin.RoutesInfo

api/server/stats.go

@@ -1,26 +0,0 @@
-package server
-
-import (
-	"github.com/fnproject/fn/api/common"
-
-	"github.com/sirupsen/logrus"
-	"go.opencensus.io/stats"
-	"go.opencensus.io/stats/view"
-)
-
-var (
-	apiRequestCountMeasure  = common.MakeMeasure("api/request_count", "Count of API requests started", stats.UnitDimensionless)
-	apiResponseCountMeasure = common.MakeMeasure("api/response_count", "API response count", stats.UnitDimensionless)
-	apiLatencyMeasure       = common.MakeMeasure("api/latency", "Latency distribution of API requests", stats.UnitMilliseconds)
-)
-
-func RegisterAPIViews(tagKeys []string, dist []float64) {
-	err := view.Register(
-		common.CreateView(apiRequestCountMeasure, view.Count(), tagKeys),
-		common.CreateView(apiResponseCountMeasure, view.Count(), tagKeys),
-		common.CreateView(apiLatencyMeasure, view.Distribution(dist...), tagKeys),
-	)
-	if err != nil {
-		logrus.WithError(err).Fatal("cannot register view")
-	}
-}

cmd/fnserver/main.go

@@ -26,7 +26,6 @@ func main() {
 
 func registerViews() {
 	keys := []string{"fn_appname", "fn_path"}
-	apiKeys := []string{"path", "method", "status"}
 
 	latencyDist := []float64{1, 10, 50, 100, 250, 500, 1000, 10000, 60000, 120000}
 
@@ -51,5 +50,5 @@ func registerViews() {
 	// Register s3 log views
 	s3.RegisterViews(keys, latencyDist)
 
-	server.RegisterAPIViews(apiKeys, latencyDist)
+	server.RegisterAPIViews([]string{}, latencyDist)
 }