SlowBackend.go

func (e Events) Track(w http.ResponseWriter, r *http.Request) {
	start := time.Now()

	var nuid, event string
	// reads the cookie value from request - (function from go standard lib - no backend op here)
 	nuidCookie, err := r.Cookie(CookieName)
	if err != nil {
		//setting var
		nuid = uuid.New()
	} else {
		//setting var
		nuid = nuidCookie.Value
	}
	// reads the content from request - (function from go standard lib)
	eventB, err := ioutil.ReadAll(r.Body)
	if err != nil {
		// edge case  - writes error doesn't track metrics
		e.log.Error("cant read request body", zap.String("message", err.Error()))
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusBadRequest)
		_, err = w.Write([]byte(`{\n"error_status":"failed",\n"error_message":"Invalid json"\n}`))
		if nil != err {
			e.log.Error("failed to write response", zap.String("message", err.Error()))
		}
		return
	}
	event = string(eventB)
	//setting var
	nuidC := http.Cookie{
		Name:    CookieName,
		Value:   nuid,
		Expires: time.Now().Add(time.Minute * time.Duration(e.conf.NIDExpiry)),
		Domain:  e.conf.DomainName,
	}
	// adds a Set-Cookie header - no back-end here
	http.SetCookie(w, &nuidC)

	tm := time.Now().UTC().Format(TIME_FORMAT)

	// extracts ip from request
	ip := getIP(r)
	//stdlib op - no backend
	data := fmt.Sprintf(EventStructure, KeyData, event, CookieName, nuid, KeyRecTime, tm, KeyIP, ip)

	// puts data to kinesis
	_, err = e.stream.PutRecord([]byte(data))
	if err != nil {
		e.log.Error(err.Error())
		w.WriteHeader(http.StatusInternalServerError)
		w.Header().Set("Access-Control-Allow-Origin", "*")
		w.Header().Set("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept")
		w.Header().Set("Content-Type", "text/plain")
		return
	}
	// writes response back ( stdlib op )
	w.WriteHeader(http.StatusOK)
	w.Header().Set("Access-Control-Allow-Origin", "*")
	w.Header().Set("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept")
	w.Header().Set("Content-Type", "text/plain")
	io.WriteString(w, Out)

	metrics.AddCounter("events")
	metrics.UpdateTimerSince("events.latency", start)
}