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

src/messages/messages.gateway.ts

@@ -16,6 +16,7 @@ import { ConnectionRequestsService } from '../connection-requests/connection-req
 import { PrismaService } from '../prisma/prisma.service';
 import { CreateMessageDto } from './dto';
 import { Logger } from '@nestjs/common';
+import { RedisPresenceService } from '../common/services/redis-presence.service';
 
 interface AuthenticatedSocket extends Socket {
   userId?: string;
@@ -44,6 +45,7 @@ export class MessagesGateway implements OnGatewayConnection, OnGatewayDisconnect
     private readonly prisma: PrismaService,
     private readonly jwtService: JwtService,
     private readonly configService: ConfigService,
+    private readonly redisPresence: RedisPresenceService,
   ) {
     // Periodic cleanup of userSocketMap and rateLimitMap every 5 minutes
     setInterval(() => {
@@ -112,6 +114,9 @@ export class MessagesGateway implements OnGatewayConnection, OnGatewayDisconnect
 
     this.logger.log(`Client connected successfully: ${client.id} (User: ${userId}, Role: ${payload.role})`);
 
+    // Join per-user room for Redis-backed cross-instance message routing
+    client.join(`user:${userId}`);
+
     // Everything below is best-effort — don't let DB errors kill the socket connection
     try {
       // Auto-join admin users to admin_room for support chat notifications
@@ -123,7 +128,11 @@ export class MessagesGateway implements OnGatewayConnection, OnGatewayDisconnect
       this.logger.warn(`Failed to join admin room for ${userId}: ${err.message}`);
     }
 
-    // Update user online status in background (don't await)
+    // Update user online status in Redis + DB (don't await)
+    this.redisPresence.setOnline(userId).catch((err) => {
+      this.logger.warn(`Failed to set Redis presence for ${userId}: ${err.message}`);
+    });
+
     this.messagesService.updateOnlineStatus(userId, true)
       .then(() => {
         this.broadcastUserStatus(userId, true);
@@ -158,13 +167,14 @@ export class MessagesGateway implements OnGatewayConnection, OnGatewayDisconnect
    */
   async handleDisconnect(client: AuthenticatedSocket) {
     if (client.userId) {
-      // Remove socket from tracking
+      // Remove socket from local tracking
       const sockets = this.userSocketMap.get(client.userId);
       if (sockets) {
         sockets.delete(client.id);
-        // Only mark offline if no more sockets connected
+        // Only mark offline if no more local sockets connected
         if (sockets.size === 0) {
           this.userSocketMap.delete(client.userId);
+          await this.redisPresence.setOffline(client.userId);
           await this.messagesService.updateOnlineStatus(client.userId, false);
           this.broadcastUserStatus(client.userId, false);
         }
@@ -245,7 +255,7 @@ export class MessagesGateway implements OnGatewayConnection, OnGatewayDisconnect
           this.sendToUser(otherUserId, 'new_message', message);
 
           // Auto-mark as DELIVERED if recipient is online
-          if (this.isUserOnline(otherUserId)) {
+          if (await this.isUserOnline(otherUserId)) {
             const deliveredAt = new Date().toISOString();
             await this.messagesService.markMessageDelivered(message.id);
             // Update message object so sender gets correct status in callback
@@ -502,25 +512,17 @@ export class MessagesGateway implements OnGatewayConnection, OnGatewayDisconnect
   }
 
   /**
-   * Send message to a specific user (by userId)
+   * Send message to a specific user via per-user room (Redis-backed cross-instance)
    */
   sendToUser(userId: string, event: string, data: any) {
-    const sockets = this.userSocketMap.get(userId);
-    if (sockets && sockets.size > 0) {
-      sockets.forEach((socketId) => {
-        this.server.to(socketId).emit(event, data);
-      });
-      this.logger.debug(`Sent ${event} to user ${userId} via ${sockets.size} socket(s)`);
-    } else {
-      this.logger.debug(`User ${userId} has no active sockets for ${event} - message saved in DB`);
-    }
+    this.server.to(`user:${userId}`).emit(event, data);
+    this.logger.debug(`Sent ${event} to user:${userId} room`);
   }
 
   /**
-   * Check if a user is online
+   * Check if a user is online (Redis-backed)
    */
-  isUserOnline(userId: string): boolean {
-    const sockets = this.userSocketMap.get(userId);
-    return sockets ? sockets.size > 0 : false;
+  async isUserOnline(userId: string): Promise<boolean> {
+    return this.redisPresence.isOnline(userId);
   }
 }