Realtime Hub Design Specification - lobbyChatHub

This document provides a detailed architectural overview of the lobbyChatHub realtime hub within the lobbyChat service. It covers the hub’s room management, message handling, role-based authorization, event system, and server-side logic.

Hub Overview

Description: Public lobby chat hub. A single shared room where all authenticated users (guests and registered) can chat in real-time. Messages have 24-hour retention. Supports moderation: report, mute, and admin removal.

• Socket.IO Namespace: /hub/lobbyChatHub
• Room DataObject: lobbyRoom

Room Settings

Rooms are backed by the lobbyRoom DataObject. Each record in this object represents a room that users can join.

Authorization Flow

The hub uses a layered authorization flow to determine each user’s role when joining a room:

1. Absolute Roles: Users with roles administrator bypass all checks and receive the system hub role with full permissions.

2. Auth Sources: The following DataObject-based authorization sources are checked in order. The first match determines the user’s hub role:

   1. allowAllAuthenticated

Hub Roles

Role	Read	Send	Moderate	Delete Any	Manage Room	Moderated
lobbyUser	Yes	Yes	No	No	No	No
moderator	Yes	Yes	Yes	Yes	No	No

• lobbyUser is restricted to message types: text

Message Settings

• Message DataObject: lobbyChatHubMessage

Built-in Message Types

The following message types are supported:

• text
• system

Cross-Cutting Features

• Reply Threading: Disabled
• Reactions: Enabled — emoji reactions supported on all message types
• Forwarded Flag: Disabled

Event Settings

Standard Events

Event	Enabled	Type
Typing Indicator	Yes	Ephemeral
Recording Indicator	No	Ephemeral
Read Receipts	No	Persisted
Delivery Receipts	No	Persisted
Presence	Yes	Ephemeral

Auto-Bridged DataObject Events

CRUD events from the room, membership, and message DataObjects are automatically bridged via Kafka and broadcast to connected clients. This includes events like memberJoined, messageEdited, roomUpdated, etc.

Custom Events

• userMuted
  • Direction: serverToRoom
  • Ephemeral: Yes
  • Broadcast when a user is muted in the lobby by an admin.
• messageModerated
  • Direction: serverToRoom
  • Ephemeral: Yes
  • Broadcast when a message is removed by admin moderation, so all users can hide it.

History Settings

Guardrails

Setting	Value
Max Users Per Room	1000
Max Rooms Per User	3
Message Rate Limit	20 msg/min
Max Message Size	4096 bytes
Connection Timeout	300000 ms
Auth Cache TTL	300 seconds
Global Moderation	No
Default Silenced	No

Server-Side Logic

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This document was generated from the realtime hub configuration and should be kept in sync with design changes.