Adding Prometheus metrics

This commit adds a '/metrics' endpoint in the API that can be exploited by Prometheus.

This endpoint returns:

- the number of connected sockets
- the number of users per room
- common NodeJS and system metrics

WARNING: this endpoint is public right now and should be protected

back/src/App.ts

@@ -6,6 +6,7 @@ import {Application, Request, Response} from 'express';
 import bodyParser = require('body-parser');
 import * as http from "http";
 import {MapController} from "./Controller/MapController";
+import {PrometheusController} from "./Controller/PrometheusController";
 
 class App {
     public app: Application;
@@ -13,6 +14,7 @@ class App {
     public ioSocketController: IoSocketController;
     public authenticateController: AuthenticateController;
     public mapController: MapController;
+    public prometheusController: PrometheusController;
 
     constructor() {
         this.app = express();
@@ -29,6 +31,7 @@ class App {
         this.ioSocketController = new IoSocketController(this.server);
         this.authenticateController = new AuthenticateController(this.app);
         this.mapController = new MapController(this.app);
+        this.prometheusController = new PrometheusController(this.app, this.ioSocketController);
     }
 
     // TODO add session user
@@ -49,4 +52,4 @@ class App {
     }
 }
 
-export default new App().server;
+export default new App().server;

back/src/Controller/IoSocketController.ts

@@ -12,6 +12,8 @@ import {SetPlayerDetailsMessage} from "_Model/Websocket/SetPlayerDetailsMessage"
 import {MessageUserJoined} from "../Model/Websocket/MessageUserJoined";
 import {MessageUserMoved} from "../Model/Websocket/MessageUserMoved";
 import si from "systeminformation";
+import {Gauge} from "prom-client";
+import os from 'os';
 
 enum SockerIoEvent {
     CONNECTION = "connection",
@@ -31,12 +33,24 @@ enum SockerIoEvent {
 }
 
 export class IoSocketController {
-    Io: socketIO.Server;
-    Worlds: Map<string, World> = new Map<string, World>();
-    sockets: Map<string, ExSocketInterface> = new Map<string, ExSocketInterface>();
+    public readonly Io: socketIO.Server;
+    private Worlds: Map<string, World> = new Map<string, World>();
+    private sockets: Map<string, ExSocketInterface> = new Map<string, ExSocketInterface>();
+    private nbClientsGauge: Gauge<string>;
+    private nbClientsPerRoomGauge: Gauge<string>;
 
     constructor(server: http.Server) {
         this.Io = socketIO(server);
+        this.nbClientsGauge = new Gauge({
+            name: 'workadventure_nb_sockets',
+            help: 'Number of connected sockets',
+            labelNames: [ 'host' ]
+        });
+        this.nbClientsPerRoomGauge = new Gauge({
+            name: 'workadventure_nb_clients_per_room',
+            help: 'Number of clients per room',
+            labelNames: [ 'host', 'room' ]
+        });
 
         // Authentication with token. it will be decoded and stored in the socket.
         // Completely commented for now, as we do not use the "/login" route at all.
@@ -103,6 +117,7 @@ export class IoSocketController {
 
             // Let's log server load when a user joins
             let srvSockets = this.Io.sockets.sockets;
+            this.nbClientsGauge.inc({ host: os.hostname() });
             console.log(new Date().toISOString() + ' A user joined (', Object.keys(srvSockets).length, ' connected users)');
             si.currentLoad().then(data => console.log('  Current load: ', data.avgload));
             si.currentLoad().then(data => console.log('  CPU: ', data.currentload, '%'));
@@ -231,6 +246,7 @@ export class IoSocketController {
 
                 // Let's log server load when a user leaves
                 let srvSockets = this.Io.sockets.sockets;
+                this.nbClientsGauge.dec({ host: os.hostname() });
                 console.log('A user left (', Object.keys(srvSockets).length, ' connected users)');
                 si.currentLoad().then(data => console.log('Current load: ', data.avgload));
                 si.currentLoad().then(data => console.log('CPU: ', data.currentload, '%'));
@@ -267,6 +283,7 @@ export class IoSocketController {
             }
             //user leave previous room
             Client.leave(Client.roomId);
+            this.nbClientsPerRoomGauge.inc({ host: os.hostname(), room: Client.roomId });
             delete Client.roomId;
         }
     }
@@ -274,6 +291,7 @@ export class IoSocketController {
     private joinRoom(Client : ExSocketInterface, roomId: string, position: Point): World {
         //join user in room
         Client.join(roomId);
+        this.nbClientsPerRoomGauge.inc({ host: os.hostname(), room: roomId });
         Client.roomId = roomId;
         Client.position = position;
 

back/src/Controller/MapController.ts

@@ -19,7 +19,7 @@ export class MapController {
     // Returns a map mapping map name to file name of the map
     getStartMap() {
         this.App.get("/start-map", (req: Request, res: Response) => {
-            return res.status(OK).send({
+            res.status(OK).send({
                 mapUrlStart: req.headers.host + "/map/files" + URL_ROOM_STARTED,
                 startInstance: "global"
             });

back/src/Controller/PrometheusController.ts

@@ -0,0 +1,20 @@
+import {Application, Request, Response} from "express";
+import {IoSocketController} from "_Controller/IoSocketController";
+const register = require('prom-client').register;
+const collectDefaultMetrics = require('prom-client').collectDefaultMetrics;
+
+export class PrometheusController {
+    constructor(private App: Application, private ioSocketController: IoSocketController) {
+        collectDefaultMetrics({
+            timeout: 10000,
+            gcDurationBuckets: [0.001, 0.01, 0.1, 1, 2, 5], // These are the default buckets.
+        });
+
+        this.App.get("/metrics", this.metrics.bind(this));
+    }
+
+    private metrics(req: Request, res: Response): void {
+        res.set('Content-Type', register.contentType);
+        res.end(register.metrics());
+    }
+}