Add additional check if the game the game server references is running

src/game-servers/services/game-servers.service.spec.ts

@@ -17,6 +17,7 @@ import {
   MongooseModule,
 } from '@nestjs/mongoose';
 import { GamesService } from '@/games/services/games.service';
+import { GameState } from '@/games/models/game-state';
 
 jest.mock('@/games/services/games.service');
 
@@ -200,7 +201,14 @@ describe('GameServersService', () => {
   describe('#findFreeGameServer()', () => {
     describe('when the server is online but taken', () => {
       beforeEach(async () => {
-        testGameServer.game = new ObjectId();
+        const game1 = await gameModel.create({
+          number: 2,
+          map: 'cp_badlands',
+          slots: [],
+          state: GameState.started
+        });
+
+        testGameServer.game = new ObjectId(game1.id);
         testGameServer.isOnline = true;
         await testGameServer.save();
       });
@@ -212,6 +220,28 @@ describe('GameServersService', () => {
       });
     });
 
+    describe('when the server has a game, but that game ended', () => {
+      beforeEach(async () => {
+
+        const game2 = await gameModel.create({
+          number: 2,
+          map: 'cp_badlands',
+          slots: [],
+          state: GameState.ended
+        });
+
+        testGameServer.game = new ObjectId(game2.id);
+        testGameServer.isOnline = true;
+        await testGameServer.save();
+      });
+
+      it('should return this game server', async () => {
+        expect((await service.findFreeGameServer()).id).toEqual(
+          testGameServer.id,
+        );
+      });
+    });
+
     describe('when the server is free but offline', () => {
       beforeEach(async () => {
         testGameServer.isOnline = false;

src/game-servers/services/game-servers.service.ts

@@ -14,6 +14,7 @@ import { InjectModel } from '@nestjs/mongoose';
 import { Model, Error, Types } from 'mongoose';
 import { GamesService } from '@/games/services/games.service';
 import { filter } from 'rxjs/operators';
+import { GameState } from '@/games/models/game-state';
 
 interface HeartbeatParams {
   name: string;
@@ -155,14 +156,41 @@ export class GameServersService implements OnModuleInit {
   }
 
   async findFreeGameServer(): Promise<GameServer> {
-    return plainToClass(
-      GameServer,
-      await this.gameServerModel
-        .findOne({ isOnline: true, game: { $exists: false } })
-        .orFail()
-        .lean()
-        .exec(),
-    );
+    let availableGameServer: GameServer = null;
+    // Fetch all game servers to determine which ones are free
+    const availableGameServers = await this.getAllGameServers();
+
+    // Iterate every server and confirm if the stored game is actually running
+    // We iterate from last to first to return the first available server of
+    // all available server instead of the last
+    for (let i = availableGameServers.length - 1; i > -1; i--) {
+      const gameServer = availableGameServers[i];
+      if (gameServer.game !== undefined) {
+        const game = await this.gamesService.getById(gameServer.game);
+
+        if (
+          game.state === GameState.ended ||
+          game.state === GameState.interrupted
+        ) {
+          this.logger.debug(
+            `game server ${gameServer.id} (${gameServer.name}) had the wrong state of a game`,
+          );
+
+          // Release the gameserver since the game it has stored actually finished
+          await this.releaseServer(gameServer.id);
+
+          availableGameServer = gameServer;
+        }
+      } else {
+        availableGameServer = gameServer;
+      }
+    }
+
+    if (availableGameServer !== null) {
+      return availableGameServer;
+    } else {
+      throw new Error.DocumentNotFoundError("No free servers available.");
+    }
   }
 
   async assignFreeGameServer(gameId: string): Promise<GameServer> {