Milestone-D4

New Features

Message Queues with Redis

Redis Pub/Sub Implementation:

• The backend now integrates Redis as a message queue using the pub/sub pattern to manage events and communication for matching events.
• Channels used include:
  • userChannel: Used to keep track of users in the matching queue.
  • matchChannel: Used for notifying matched users.
  • timeoutChannel: Used for notifying users who have been timed out.

Matching Service

• Websocket namespace /match exposed via Socket.IO to handle matching service
  • Accessible via ws://localhost:4000/match?userId=<USER_ID>
• The WebSocket now enforces that only valid userIds (based on Mongoose validation) are allowed to connect.
• All WebSocket payloads that involve a userId must match the userId used during the connection handshake.
• A single userId can only be used to establish one connection to the /match namespace.

Summary of Updated Events

Event Type	Event Name	Payload/Response	Description
Backend Listens to	findMatch	{ userId: string, selectedTopic: string[], selectedDifficulty: string }	Triggered when a user requests to find a match.
	cancelMatch	{ userId: string }	Triggered when a user cancels their match request.
	acceptMatch	{ userId: string, matchId: string }	Triggered when a user accepts a match they have received.
	declineMatch	{ userId: string, matchId: string }	Triggered when a user declines a match they have received.
Backend Emits	matchRequested	{ message: string }	Sent to the user after they successfully request a match.
	matchCancelled	{ message: string }	Sent when a user cancels their match request or declines a match.
	matchFound	{ message: string, matchUserId: string, matchId: string }	Sent to both users when a match is found for them.
	matchAccepted	{ message: string }	Sent to a user who accepts a match while waiting for the other user to accept.
	matchDeclined	{ message: string }	Sent to the other user when one user declines the match.
	matchConfirmed	{ message: string, sessionId: string }	Sent to both users when both have accepted the match, and a session is created.
	matchError	{ message: string }	Sent to a user when an error occurs during the match request, acceptance, or cancellation process.
	matchTimeout	{ message: string, timedOutUserId: string }	Sent to a user when they have been timed out due to inactivity or no matches found.
	exception	{ message: string }	Sent when an error occurs, typically during connection or match operations.

Key Updates

Centralised Env Configuration

• Added a new config object for each service in configs/env.config.ts to centralise environment variables importing and error checking.

Docker Compose Update

• Added a new matching-service to the docker-compose.yml file