Prometheus example

prometheus_getsetvalues.go

 package main

import (
	"log"
	"net/http"
	"time"

	"github.com/alexellis/faas/gateway/metrics"
	"github.com/gorilla/mux"
	"github.com/prometheus/client_golang/prometheus"
	io_prometheus_client "github.com/prometheus/client_model/go"
)

func main() {

	gatewayFunctionInvocation := prometheus.NewCounterVec(
		prometheus.CounterOpts{
			Name: "gateway_function_invocation_total",
			Help: "Individual function metrics",
		},
		[]string{"function_name", "http_code"},
	)

	r := mux.NewRouter()
	metricsHandler := metrics.PrometheusHandler()
	r.Handle("/metrics", metricsHandler)

	r.PathPrefix("/").Handler(http.FileServer(http.Dir("./assets/"))).Methods("GET")
	s := &http.Server{
		Addr:           ":8080",
		ReadTimeout:    8 * time.Second,
		WriteTimeout:   8 * time.Second,
		MaxHeaderBytes: 1 << 20,
		Handler:        r,
	}

	serviceName := "main"
	labels := prometheus.Labels{"http_code": "500", "function_name": serviceName}
	gatewayFunctionInvocation.With(labels).Add(1)

	labelsOK := prometheus.Labels{"http_code": "200", "function_name": serviceName}
	gatewayFunctionInvocation.With(labelsOK).Add(1)
	
	prometheus.Register(gatewayFunctionInvocation)

	// ideally this would work giving 2, but technically matches nothing. 
	allCodesForService := prometheus.Labels{"http_code": "", "function_name": serviceName}

	counter := gatewayFunctionInvocation.With(allCodesForService)

	// Get the metric's value from ProtoBuf interface (idea via Julius Volz)
	var protoMetric io_prometheus_client.Metric
	counter.Write(&protoMetric)
	invocations := protoMetric.GetCounter().GetValue()
	log.Println(invocations)

	log.Fatal(s.ListenAndServe())
}