Auto-delete rooms after 10 minutes of inactivity

app/server/index.js

@@ -55,6 +55,7 @@ io.on('connection', (socket) => {
     let room = roomManager.getRoom(roomCode);
     if (room) {
       console.log(`join room by ${userId}`);
+      roomManager.markRoomAsActive(room);
       let localPlayer = room.connectPlayer({ userId, socket });
       let status;
       if (localPlayer) {
@@ -231,6 +232,11 @@ io.on('connection', (socket) => {
       console.log('unset player socket');
       socket.user.socket = null;
     }
+    // As soon as both players disconnect from the room (making it completely
+    // empty), mark the room for deletion
+    if (socket.room && !socket.room.isActive()) {
+      roomManager.markRoomAsInactive(socket.room);
+    }
   });
 
 });

app/server/room-manager.js

@@ -1,9 +1,13 @@
+import moment from 'moment';
+
 import Room from './room.js';
 
 class RoomManager {
 
   constructor() {
     this.roomsById = {};
+    this.inactiveRooms = new Set();
+    this.pollForAbandonedRooms();
   }
 
   getRoom(roomCode) {
@@ -43,9 +47,39 @@ class RoomManager {
     return roomCode;
   }
 
+  markRoomAsActive(room) {
+    this.inactiveRooms.delete(room);
+    room.lastMarkedInactive = null;
+    console.log(`room ${room.code} is active again`);
+  }
+
+  markRoomAsInactive(room) {
+    room.lastMarkedInactive = Date.now();
+    this.inactiveRooms.add(room);
+    console.log(`room ${room.code} marked as inactive`);
+  }
+
+  // A room is considered "abandoned" if it has been inactive for more than the
+  // specified period of time
+  pollForAbandonedRooms() {
+    setInterval(() => {
+      this.inactiveRooms.forEach((room) => {
+        if (room.isAbandoned()) {
+          // Yes, it is safe to remove elements from a Set while iterating over
+          // it; see <https://stackoverflow.com/a/28306768/560642>
+          this.inactiveRooms.delete(room);
+          delete this.roomsById[room.code];
+          console.log(`room ${room.code} has been permanently deleted`);
+        }
+      });
+    }, Room.abandonmentCheckInterval.asMilliseconds());
+  }
+
 }
 
 // The number of characters is a given room code
 RoomManager.roomCodeLength = 4;
+// How frequently (in minutes) to check for abandoned rooms
+Room.abandonmentCheckInterval = moment.duration(30, 'minutes');
 
 export default RoomManager;

app/server/room.js

@@ -1,3 +1,5 @@
+import moment from 'moment';
+
 import Player from './player.js';
 import Game from './game.js';
 
@@ -7,13 +9,17 @@ class Room {
     this.code = code;
     this.players = players;
     this.game = game;
+    // The date/time the room was last seen completely empty (i.e. both players
+    // were disconnected)
+    this.lastMarkedInactive = null;
   }
 
   addPlayer({ player, socket }) {
     player = new Player(player);
     this.players.push(player);
     player.socket = socket;
     socket.user = player;
+    socket.room = this;
     socket.join(this.code);
     return player;
   }
@@ -31,11 +37,28 @@ class Room {
     if (player) {
       player.socket = socket;
       socket.user = player;
+      socket.room = this;
       socket.join(this.code);
     }
     return player;
   }
 
+  // Return true if at least one player is currently connected to the room,
+  // otherwise return false
+  isActive() {
+    return this.players.some((player) => player.socket !== null);
+  }
+
+  isAbandoned() {
+    return moment(this.lastMarkedInactive)
+      .add(Room.abandonmentThreshold)
+      .isSameOrBefore(moment());
+  }
+
 }
 
+// The number of minutes a room can be inactive before it is considered
+// abandoned (and thus subject to automatic deletion by the RoomManager)
+Room.abandonmentThreshold = moment.duration(10, 'minutes');
+
 export default Room;

package.json

@@ -33,6 +33,7 @@
     "express": "^4.17.1",
     "fastclick": "^1.0.6",
     "mithril": "github:MithrilJS/mithril.js#deaf01c8e96446c97f31826b1d04ab4a4e757718",
+    "moment": "^2.24.0",
     "random": "^2.1.1",
     "socket.io": "^2.2.0",
     "socket.io-client": "^2.2.0",