Basic Prometheus metrics on server-side

client/.eslintrc.json

@@ -22,4 +22,4 @@
         "space-infix-ops": "error",
         "no-unused-vars": "off"
     }
-}
+}

client/src/index.js

@@ -132,4 +132,4 @@ const config = {
 
 const game = new Phaser.Game(config);
 
-window.addEventListener('resize', () => game.scale.resize(window.innerWidth, window.innerHeight));
+window.addEventListener('resize', () => game.scale.resize(window.innerWidth, window.innerHeight));

client/src/objects/player.js

@@ -57,5 +57,4 @@ export class Player extends Phaser.Physics.Arcade.Sprite {
             this.setTexture('stand');
         }
     }
-}
-
+}

server/cmd/ptrun-server/main.go

@@ -3,18 +3,22 @@ package main
 import (
 	"context"
 	"fmt"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+	"github.com/spf13/cobra"
 	"net/http"
 	"os"
 	"os/signal"
 	"syscall"
 	"time"
 
-	"github.com/spf13/cobra"
 	"go.uber.org/zap"
 	"goji.io"
 	"goji.io/pat"
 
 	"github.com/ptr-geeks/ptrun/server/internal/ws"
+
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 )
 
 var (
@@ -28,6 +32,13 @@ type ServerConfig struct {
 	Path  string
 }
 
+var (
+	state = promauto.NewGauge(prometheus.GaugeOpts{
+		Name: "ptrun_state",
+		Help: "State",
+	})
+)
+
 func main() {
 	config := ServerConfig{}
 
@@ -66,19 +77,27 @@ func run(config *ServerConfig) {
 
 	sugared := logger.Sugar()
 
+	state.Set(0)
+
+	mux := goji.NewMux()
+	mux.HandleFunc(pat.Get("/ws"), func(w http.ResponseWriter, r *http.Request) {
+		server.Connect(w, r)
+	})
+	mux.HandleFunc(pat.Get("/metrics"), func(w http.ResponseWriter, r *http.Request) {
+		prometheus := promhttp.Handler()
+		prometheus.ServeHTTP(w, r)
+	})
+
 	server = ws.NewServer(logger)
 	go server.Run()
 
+	// TODO: We should allow some overrides by passing parameters to our executable
+	// Example: ./ptr-server --port 8080 --path "/ws"
 	sugared.Infow("starting websocket endpoint",
 		"host", config.Host,
 		"port", config.Port,
 		"path", config.Path)
 
-	mux := goji.NewMux()
-	mux.HandleFunc(pat.Get(config.Path), func(w http.ResponseWriter, r *http.Request) {
-		server.Connect(w, r)
-	})
-
 	srv := &http.Server{
 		Handler: mux,
 		Addr:    fmt.Sprintf("%s:%s", config.Host, config.Port),
@@ -90,9 +109,11 @@ func run(config *ServerConfig) {
 
 	done := make(chan os.Signal, 1)
 	signal.Notify(done, os.Interrupt, syscall.SIGINT, syscall.SIGTERM)
+	state.Set(1)
 
 	go func() {
 		if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
+			state.Set(2)
 			sugared.Errorw("error starting http server", zap.Error(err))
 		}
 	}()

server/go.mod

@@ -5,6 +5,7 @@ go 1.15
 require (
 	github.com/asaskevich/EventBus v0.0.0-20200907212545-49d423059eef
 	github.com/gorilla/websocket v1.4.2
+	github.com/prometheus/client_golang v1.11.0
 	github.com/spf13/cobra v1.2.1
 	go.uber.org/zap v1.19.0
 	goji.io v2.0.2+incompatible

server/internal/ws/server.go

@@ -1,6 +1,8 @@
 package ws
 
 import (
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
 	"net/http"
 
 	"github.com/gorilla/websocket"
@@ -23,6 +25,13 @@ var (
 	}
 )
 
+var (
+	clientscounter = promauto.NewCounter(prometheus.CounterOpts{
+		Name: "ptrun_client_counter",
+		Help: "Currently connected clients in WebSockets",
+	})
+)
+
 // serevrImpl has data about all clients
 // and sends the connect and disconnect messages
 type serverImpl struct {
@@ -65,6 +74,7 @@ func (s *serverImpl) Run() {
 	for {
 		select {
 		case connect := <-s.connect:
+			clientscounter.Inc()
 			s.logger.Infow("new connection", "remoteAddr", connect.conn.RemoteAddr())
 			client := NewClient(connect.conn, s, s.logger.Desugar())
 			s.clients[client.GetID()] = client

server/internal/ws/types.go

@@ -13,6 +13,7 @@ type Server interface {
 
 	Connect(w http.ResponseWriter, r *http.Request) Client
 	Disconnect(client Client)
+
 	Broadcast(excludeClient int32, msg *messages.Message)
 }