작업 이유

• Authenticated User can join chatroom

작업 사항

1️⃣ Domain Business Rule

• Domain Aspect
  • Password Requirements (Controller Layer): Password must be a six-digit integer. Null values are allowed for public rooms.
  • User Authentication (Security Layer): User must be authenticated.
  • Chatroom Capacity (Application Layer): Chatroom can accommodate up to 300 users
  • Password Match (Application Layer): Chatroom's password must match for entry.
  • User Validation (Domain Layer): User shouldn't be currently a member or have a ban history in the chatroom.
  • Immutability Check (Domain Layer): Fields like name and role in chat members are immutable.
  • New Join Handling (Application Layer): At the end of the service, handle the new join message within the chatroom.
  • When a user joins the chatroom, a new join message is implicitly handled within the chatroom.
• Infrastructure Aspect
  • Concurrent Join Handling: If 350 users try to join simultaneously, only the first 299 will succeed (requires Distributed Lock).
  • If the chatroom resource is committed, a message must be sent to the queue at least once. (requires transaction rollback & message broker)

2️⃣ Refined Chatroom Join API with Bounded-Context Design

If you want more details, read my blog

• We can implement this feature in two way
  1. Implement all feature in the socket application
  2. Separate HTTP requests from socket requests.
• Choosing the first approach may violate principles of separation of concerns and bounded-context:
  • WebSocket’s role should focus on real-time message routing.
  • The creation of chat-member resources, however, is better managed through REST API.
• Consequently, Chat-member context should be handled via HTTP API, while message context should remain within the socket.

3️⃣ Unit Test

• Verify Business Rules:
  • Confirm chatroom capacity limits are enforced (e.g., chatroom is full).
  • Validate the provided password is correct.
  • Ensure events are published as expected.
• Exceptional Cases:
  • Handle cases where the chatroom does not exist.
  • Address scenarios with missing user data.
  • Manage cases with incorrect passwords.

4️⃣ Integration Test

• Distributed Lock Verification
  • Simultaneous room join scenario.
  • Confirm correct lock acquisition and release.
• Transaction Verification
  • Test rollback functionality.
  • Ensure data consistency.
• Flow Verification
  • Test happy path scenarios.
  • Verify real data is saved and received as expected.

리뷰어가 중점적으로 확인해야 하는 부분

• I mapped out a design as though we have a socket-relay module, but it’s purely conceptual at this point.
  • This is because our server lacks sufficient memory for a full implementation. 😂
  • Therefore, I’ll proceed by implementing this feature within the socket application itself.
• The remaining, unrelated tasks will be deferred to the next stage for completion (ex. socket-relay module)

발견한 이슈

• When testing ApplicationEventPublisher and EventHandler using mocks in an integration test, @RecordingEvents and verify() cannot be used directly.
  • This is because ApplicationEventPublisher is part of the Spring context itself, meaning @MockBean won’t work in this instance.
  • Therefore, ApplicationEventPublisher cannot act as a mock instance.
  • Additionally, when you mock event handlers, ApplicationEvents will not accurately capture event counts.
  • Instead, an alternative approach should be used for event capture.

      ArgumentCaptor<ChatRoomJoinEvent> eventCaptor = ArgumentCaptor.forClass(ChatRoomJoinEvent.class);
    
      // when
      ResponseEntity<?> response = postJoining(user, chatRoom.getId(), new ChatMemberReq.Join(null));
    
      // then
      assertAll(
              () -> assertEquals(HttpStatus.OK, response.getStatusCode()),
              () -> assertTrue(chatMemberRepository.existsByChatRoomIdAndUserId(chatRoom.getId(), user.getId())),
              () -> verify(chatRoomJoinEventHandler).handle(eventCaptor.capture()),
              () -> {
                  ChatRoomJoinEvent capturedEvent = eventCaptor.getValue();
                  assertEquals(chatRoom.getId(), capturedEvent.chatRoomId());
                  assertEquals(user.getName(), capturedEvent.userName());
              }
      );