feat: implement Redis-backed Socket.io adapter and user presence service for cross-instance communication

src/common/adapters/redis-io.adapter.ts

@@ -0,0 +1,42 @@
+import { IoAdapter } from '@nestjs/platform-socket.io';
+import { INestApplicationContext, Logger } from '@nestjs/common';
+import { ConfigService } from '@nestjs/config';
+import { ServerOptions } from 'socket.io';
+import { createAdapter } from '@socket.io/redis-adapter';
+import Redis from 'ioredis';
+
+export class RedisIoAdapter extends IoAdapter {
+  private readonly logger = new Logger(RedisIoAdapter.name);
+  private adapterConstructor: ReturnType<typeof createAdapter>;
+
+  constructor(
+    app: INestApplicationContext,
+    private readonly configService: ConfigService,
+  ) {
+    super(app);
+  }
+
+  async connectToRedis(): Promise<void> {
+    const host = this.configService.get<string>('redis.host', 'localhost');
+    const port = this.configService.get<number>('redis.port', 6379);
+    const password = this.configService.get<string>('redis.password') || undefined;
+    const db = this.configService.get<number>('redis.db', 0);
+
+    const pubClient = new Redis({ host, port, password, db });
+    const subClient = new Redis({ host, port, password, db });
+
+    await Promise.all([
+      new Promise<void>((resolve) => pubClient.on('connect', resolve)),
+      new Promise<void>((resolve) => subClient.on('connect', resolve)),
+    ]);
+
+    this.adapterConstructor = createAdapter(pubClient, subClient);
+    this.logger.log(`Redis adapter connected to ${host}:${port}`);
+  }
+
+  createIOServer(port: number, options?: ServerOptions) {
+    const server = super.createIOServer(port, options);
+    server.adapter(this.adapterConstructor);
+    return server;
+  }
+}