feat(realtime): Socket.IO Redis adapter — enable horizontal scaling

- RedisIoAdapter wires @socket.io/redis-adapter with dedicated pub/sub clients
- channel key 'tripz:sio' isolates on shared Redis
- wired in main.ts via useWebSocketAdapter; multiple app replicas can now share WS connections

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/package.json

@@ -29,6 +29,7 @@
     "@nestjs/throttler": "^6.2.0",
     "@nestjs/typeorm": "^11.0.0",
     "@nestjs/websockets": "^11.0.0",
+    "@socket.io/redis-adapter": "^8.3.0",
     "bullmq": "^5.12.0",
     "class-transformer": "^0.5.1",
     "class-validator": "^0.14.1",

backend/src/main.ts

@@ -4,11 +4,17 @@ import { ValidationPipe, Logger } from '@nestjs/common';
 import { ConfigService } from '@nestjs/config';
 import { DocumentBuilder, SwaggerModule } from '@nestjs/swagger';
 import { AppModule } from './app.module';
+import { RedisIoAdapter } from './realtime/redis-io.adapter';
 
 async function bootstrap() {
   const app = await NestFactory.create(AppModule);
   const cfg = app.get(ConfigService);
 
+  // مُحوّل Socket.IO عبر Redis — يفعّل التوسّع الأفقي (عدة نسخ)
+  const redisIoAdapter = new RedisIoAdapter(app, cfg);
+  await redisIoAdapter.connectToRedis();
+  app.useWebSocketAdapter(redisIoAdapter);
+
   app.setGlobalPrefix('api');
   app.useGlobalPipes(
     new ValidationPipe({ whitelist: true, transform: true }),

backend/src/realtime/redis-io.adapter.ts

@@ -0,0 +1,46 @@
+import { INestApplicationContext, Logger } from '@nestjs/common';
+import { ConfigService } from '@nestjs/config';
+import { IoAdapter } from '@nestjs/platform-socket.io';
+import { ServerOptions } from 'socket.io';
+import { createAdapter } from '@socket.io/redis-adapter';
+import Redis from 'ioredis';
+
+/**
+ * مُحوّل Socket.IO مدعوم بـ Redis — يجعل التطبيق قابلاً للتشغيل بعدة نسخ
+ * (توسّع أفقي) تتشارك اتصالات الويب سوكت عبر Redis. بلا هذا، رسالة من نسخة
+ * لا تصل زبوناً متصلاً بنسخة أخرى (راجع docs/09).
+ * مفتاح القنوات ببادئة tripz للعزل عن أي تطبيق آخر على نفس Redis.
+ */
+export class RedisIoAdapter extends IoAdapter {
+  private readonly logger = new Logger('SocketRedis');
+  private adapterConstructor: ReturnType<typeof createAdapter>;
+
+  constructor(
+    app: INestApplicationContext,
+    private readonly config: ConfigService,
+  ) {
+    super(app);
+  }
+
+  async connectToRedis(): Promise<void> {
+    const opts = {
+      host: this.config.get<string>('redis.host'),
+      port: this.config.get<number>('redis.port'),
+      db: this.config.get<number>('redis.db'),
+      maxRetriesPerRequest: null,
+    };
+    const pub = new Redis(opts);
+    const sub = pub.duplicate();
+    pub.on('error', (e) => this.logger.warn(`pub: ${e.message}`));
+    sub.on('error', (e) => this.logger.warn(`sub: ${e.message}`));
+    // key يعزل قنوات socket.io الخاصة بـ Tripz عن غيرها على نفس Redis
+    this.adapterConstructor = createAdapter(pub, sub, { key: 'tripz:sio' });
+    this.logger.log('Socket.IO Redis adapter ready (horizontal scale enabled)');
+  }
+
+  createIOServer(port: number, options?: ServerOptions): any {
+    const server = super.createIOServer(port, options);
+    if (this.adapterConstructor) server.adapter(this.adapterConstructor);
+    return server;
+  }
+}