add span attributes to frontend (open-telemetry#82)

* add manual instrumentation to frontend

* frontend span attributes

CHANGELOG.md

@@ -15,3 +15,5 @@ release.
   future significant modifications will be credited to OpenTelemetry Authors.
 * Added feature flag service protos
   ([#26](https://github.com/open-telemetry/opentelemetry-demo-webstore/pull/26))
+* Added span attributes to frontend service
+  ([#82](https://github.com/open-telemetry/opentelemetry-demo-webstore/pull/82))

src/frontend/handlers.go

@@ -17,6 +17,10 @@ package main
 import (
 	"context"
 	"fmt"
+	"github.com/GoogleCloudPlatform/microservices-demo/src/frontend/instr"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/codes"
+	"go.opentelemetry.io/otel/trace"
 	"html/template"
 	"math/rand"
 	"net"
@@ -102,6 +106,12 @@ func (fe *frontendServer) homeHandler(w http.ResponseWriter, r *http.Request) {
 	plat = platformDetails{}
 	plat.setPlatformDetails(strings.ToLower(env))
 
+	span := trace.SpanFromContext(r.Context())
+	span.SetAttributes(
+		attribute.Int(instr.AppPrefix+"products.count", len(products)),
+		attribute.Int(instr.AppPrefix+"cart.size", cartSize(cart)),
+	)
+
 	if err := templates.ExecuteTemplate(w, "home", map[string]interface{}{
 		"session_id":        sessionID(r),
 		"request_id":        r.Context().Value(ctxKeyRequestID{}),
@@ -117,6 +127,7 @@ func (fe *frontendServer) homeHandler(w http.ResponseWriter, r *http.Request) {
 		"is_cymbal_brand":   isCymbalBrand,
 		"deploymentDetails": deploymentDetailsMap,
 	}); err != nil {
+		span.SetStatus(codes.Error, err.Error())
 		log.Error(err)
 	}
 }
@@ -187,6 +198,12 @@ func (fe *frontendServer) productHandler(w http.ResponseWriter, r *http.Request)
 		Price *pb.Money
 	}{p, price}
 
+	span := trace.SpanFromContext(r.Context())
+	span.SetAttributes(
+		attribute.String(instr.AppPrefix+"product.id", id),
+		attribute.Int(instr.AppPrefix+"cart.size", cartSize(cart)),
+	)
+
 	if err := templates.ExecuteTemplate(w, "product", map[string]interface{}{
 		"session_id":        sessionID(r),
 		"request_id":        r.Context().Value(ctxKeyRequestID{}),
@@ -202,6 +219,7 @@ func (fe *frontendServer) productHandler(w http.ResponseWriter, r *http.Request)
 		"is_cymbal_brand":   isCymbalBrand,
 		"deploymentDetails": deploymentDetailsMap,
 	}); err != nil {
+		span.SetStatus(codes.Error, err.Error())
 		log.Println(err)
 	}
 }
@@ -222,6 +240,12 @@ func (fe *frontendServer) addToCartHandler(w http.ResponseWriter, r *http.Reques
 		return
 	}
 
+	span := trace.SpanFromContext(r.Context())
+	span.SetAttributes(
+		attribute.String(instr.AppPrefix+"product.id", productID),
+		attribute.Int(instr.AppPrefix+"product.quantity", int(quantity)),
+	)
+
 	if err := fe.insertCart(r.Context(), sessionID(r), p.GetId(), int32(quantity)); err != nil {
 		renderHTTPError(log, r, w, errors.Wrap(err, "failed to add to cart"), http.StatusInternalServerError)
 		return
@@ -297,6 +321,17 @@ func (fe *frontendServer) viewCartHandler(w http.ResponseWriter, r *http.Request
 	totalPrice = money.Must(money.Sum(totalPrice, shippingCost))
 	year := time.Now().Year()
 
+	// add cart details to span as a manually created attributes
+	shippingCostFloat, _ := strconv.ParseFloat(fmt.Sprintf("%d.%02d", shippingCost.GetUnits(), shippingCost.GetNanos()/10000000), 64)
+	totalPriceFloat, _ := strconv.ParseFloat(fmt.Sprintf("%d.%02d", totalPrice.GetUnits(), totalPrice.GetNanos()/10000000), 64)
+	span := trace.SpanFromContext(r.Context())
+	span.SetAttributes(
+		attribute.Int(instr.AppPrefix+"cart.size", cartSize(cart)),
+		attribute.Int(instr.AppPrefix+"cart.items.count", len(items)),
+		attribute.Float64(instr.AppPrefix+"cart.shipping.cost", shippingCostFloat),
+		attribute.Float64(instr.AppPrefix+"cart.total.price", totalPriceFloat),
+	)
+
 	if err := templates.ExecuteTemplate(w, "cart", map[string]interface{}{
 		"session_id":        sessionID(r),
 		"request_id":        r.Context().Value(ctxKeyRequestID{}),
@@ -314,6 +349,7 @@ func (fe *frontendServer) viewCartHandler(w http.ResponseWriter, r *http.Request
 		"is_cymbal_brand":   isCymbalBrand,
 		"deploymentDetails": deploymentDetailsMap,
 	}); err != nil {
+		span.SetStatus(codes.Error, err.Error())
 		log.Println(err)
 	}
 }
@@ -367,6 +403,11 @@ func (fe *frontendServer) placeOrderHandler(w http.ResponseWriter, r *http.Reque
 		totalPaid = money.Must(money.Sum(totalPaid, multPrice))
 	}
 
+	// add Order total paid to span as a manually created attribute
+	totalPaidFloat, _ := strconv.ParseFloat(fmt.Sprintf("%d.%02d", totalPaid.GetUnits(), totalPaid.GetNanos()/10000000), 64)
+	span := trace.SpanFromContext(r.Context())
+	span.SetAttributes(attribute.Float64(instr.AppPrefix+"order.total", totalPaidFloat))
+
 	currencies, err := fe.getCurrencies(r.Context())
 	if err != nil {
 		renderHTTPError(log, r, w, errors.Wrap(err, "could not retrieve currencies"), http.StatusInternalServerError)
@@ -387,6 +428,7 @@ func (fe *frontendServer) placeOrderHandler(w http.ResponseWriter, r *http.Reque
 		"is_cymbal_brand":   isCymbalBrand,
 		"deploymentDetails": deploymentDetailsMap,
 	}); err != nil {
+		span.SetStatus(codes.Error, err.Error())
 		log.Println(err)
 	}
 }
@@ -410,6 +452,8 @@ func (fe *frontendServer) setCurrencyHandler(w http.ResponseWriter, r *http.Requ
 		Debug("setting currency")
 
 	if cur != "" {
+		span := trace.SpanFromContext(r.Context())
+		span.SetAttributes(attribute.String(instr.AppPrefix+"currency.new", cur))
 		http.SetCookie(w, &http.Cookie{
 			Name:   cookieCurrency,
 			Value:  cur,
@@ -439,6 +483,10 @@ func renderHTTPError(log logrus.FieldLogger, r *http.Request, w http.ResponseWri
 	log.WithField("error", err).Error("request error")
 	errMsg := fmt.Sprintf("%+v", err)
 
+	// set span status on error
+	span := trace.SpanFromContext(r.Context())
+	span.SetStatus(codes.Error, errMsg)
+
 	w.WriteHeader(code)
 
 	if templateErr := templates.ExecuteTemplate(w, "error", map[string]interface{}{

src/frontend/instr/conventions.go

@@ -0,0 +1,13 @@
+package instr
+
+import "go.opentelemetry.io/otel/attribute"
+
+const AppPrefix = "app."
+
+const (
+	SessionId = attribute.Key(AppPrefix + "session.id")
+	RequestId = attribute.Key(AppPrefix + "request.id")
+	UserId    = attribute.Key(AppPrefix + "user.id")
+
+	Currency = attribute.Key(AppPrefix + "currency")
+)

src/frontend/main.go

@@ -130,14 +130,14 @@ func main() {
 
 	r := mux.NewRouter()
 	r.Use(otelmux.Middleware("server"))
-	r.HandleFunc("/", svc.homeHandler).Methods(http.MethodGet, http.MethodHead)
-	r.HandleFunc("/product/{id}", svc.productHandler).Methods(http.MethodGet, http.MethodHead)
-	r.HandleFunc("/cart", svc.viewCartHandler).Methods(http.MethodGet, http.MethodHead)
-	r.HandleFunc("/cart", svc.addToCartHandler).Methods(http.MethodPost)
-	r.HandleFunc("/cart/empty", svc.emptyCartHandler).Methods(http.MethodPost)
-	r.HandleFunc("/setCurrency", svc.setCurrencyHandler).Methods(http.MethodPost)
-	r.HandleFunc("/logout", svc.logoutHandler).Methods(http.MethodGet)
-	r.HandleFunc("/cart/checkout", svc.placeOrderHandler).Methods(http.MethodPost)
+	r.HandleFunc("/", instrumentHandler(svc.homeHandler)).Methods(http.MethodGet, http.MethodHead)
+	r.HandleFunc("/product/{id}", instrumentHandler(svc.productHandler)).Methods(http.MethodGet, http.MethodHead)
+	r.HandleFunc("/cart", instrumentHandler(svc.viewCartHandler)).Methods(http.MethodGet, http.MethodHead)
+	r.HandleFunc("/cart", instrumentHandler(svc.addToCartHandler)).Methods(http.MethodPost)
+	r.HandleFunc("/cart/empty", instrumentHandler(svc.emptyCartHandler)).Methods(http.MethodPost)
+	r.HandleFunc("/setCurrency", instrumentHandler(svc.setCurrencyHandler)).Methods(http.MethodPost)
+	r.HandleFunc("/logout", instrumentHandler(svc.logoutHandler)).Methods(http.MethodGet)
+	r.HandleFunc("/cart/checkout", instrumentHandler(svc.placeOrderHandler)).Methods(http.MethodPost)
 	r.PathPrefix("/static/").Handler(http.StripPrefix("/static/", http.FileServer(http.Dir("./static/"))))
 	r.HandleFunc("/robots.txt", func(w http.ResponseWriter, _ *http.Request) { fmt.Fprint(w, "User-agent: *\nDisallow: /") })
 	r.HandleFunc("/_healthz", func(w http.ResponseWriter, _ *http.Request) { fmt.Fprint(w, "ok") })

src/frontend/middleware.go

@@ -16,6 +16,8 @@ package main
 
 import (
 	"context"
+	"github.com/GoogleCloudPlatform/microservices-demo/src/frontend/instr"
+	"go.opentelemetry.io/otel/trace"
 	"net/http"
 	"time"
 
@@ -26,6 +28,8 @@ import (
 type ctxKeyLog struct{}
 type ctxKeyRequestID struct{}
 
+type httpHandler func(w http.ResponseWriter, r *http.Request)
+
 type logHandler struct {
 	log  *logrus.Logger
 	next http.Handler
@@ -81,6 +85,32 @@ func (lh *logHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	lh.next.ServeHTTP(rr, r)
 }
 
+func instrumentHandler(fn httpHandler) httpHandler {
+	// Add common attributes to the span for each handler
+	// session, request, currency, and user
+
+	return func(w http.ResponseWriter, r *http.Request) {
+		rid := r.Context().Value(ctxKeyRequestID{})
+		requestID := ""
+		if rid != nil {
+			requestID = rid.(string)
+		}
+		span := trace.SpanFromContext(r.Context())
+		span.SetAttributes(
+			instr.SessionId.String(sessionID(r)),
+			instr.RequestId.String(requestID),
+			instr.Currency.String(currentCurrency(r)),
+		)
+
+		email := r.FormValue("email")
+		if email != "" {
+			span.SetAttributes(instr.UserId.String(email))
+		}
+
+		fn(w, r)
+	}
+}
+
 func ensureSessionID(next http.Handler) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		var sessionID string