Forum API - Microservices Architecture

A modern forum application built with .NET 10.0 using microservices architecture, implementing Domain-Driven Design (DDD) principles, CQRS pattern, and event-driven communication.

📋 Overview

This project is a distributed forum system composed of three main microservices that handle different aspects of the application:

• Forum Service: Manages questions, answers, and forum-related operations
• User Service: Handles authentication, authorization, and user management
• Notification Service: Processes and delivers notifications to users

🏗️ Architecture

The project follows a microservices architecture with the following characteristics:

• Domain-Driven Design (DDD): Each service is organized around business domains
• Clean Architecture: Clear separation of concerns with distinct layers (Domain, Application, Infrastructure, Endpoints)
• Event-Driven Communication: Microservices communicate through integration events
• CQRS Pattern: Separation of read and write operations
• Minimal API: Using .NET's minimal API approach for lightweight endpoints

Building Blocks

The project includes a shared BuildingBlocks library that provides:

• Base Domain Classes: Aggregate, Entity, ValueObject, UniqueEntityId, WatchedList
• Event Bus: Implementation for both in-memory and RabbitMQ-based event publishing
• Custom Exceptions: Domain-specific exception handling (BadRequest, NotFound, Validation, etc.)
• Middleware: Correlation ID tracking, Request/Response logging
• Logging: Structured logging with Serilog
• Pagination: Generic pagination support
• Result Pattern: Functional error handling

🚀 Technologies

Core Framework

• .NET 10.0 - Latest .NET framework
• C# 13 - Modern C# features
• ASP.NET Core - Web framework with Minimal APIs

Databases

• PostgreSQL - Primary database for all services
• Entity Framework Core 10.0 - ORM for database access
• Npgsql - PostgreSQL provider for EF Core

Message Broker

• RabbitMQ - Message broker for asynchronous communication between services
• RabbitMQ.Client 6.8.1 - RabbitMQ client library

Authentication & Security

• ASP.NET Core Identity - User management framework
• JWT Bearer Authentication - Token-based authentication
• Microsoft.IdentityModel.Tokens - JWT token handling

Logging & Monitoring

• Serilog - Structured logging
• Serilog.AspNetCore - ASP.NET Core integration
• Serilog.Sinks.Console - Console output
• Serilog.Sinks.File - File-based logging
• Serilog.Expressions - Advanced logging expressions

API Documentation

• Swagger/OpenAPI - API documentation and testing interface
• Swashbuckle.AspNetCore - Swagger generator for ASP.NET Core

DevOps & Containerization

• Docker - Container platform
• Docker Compose - Multi-container orchestration

Testing

• xUnit - Testing framework
• In-Memory Database - For unit and integration testing

📊 Database Schema

Each microservice has its own dedicated database:

• ForumDb: Stores questions, answers, attachments, and forum-related data
• UserDb: Manages user accounts, roles, and authentication data
• NotificationDb: Handles notification records and delivery status

🔌 Port Mapping

Microservices

Service	Local HTTP	Local HTTPS	Docker HTTP	Docker HTTPS	Docker Internal
Forum	5000	5050	8000	8443	8080 - 8081
Notification	5001	5051	8001	8444	8080 - 8081
User	5002	5052	8002	8445	8080 - 8081

Note: Docker uses safe ports (8000-8002, 8443-8445) to avoid browser blocking issues. Ports 6000-6007 are considered unsafe by modern browsers.

Infrastructure

Service	Port	Management Port
ForumDb	5433	-
NotificationDb	5434	-
UserDb	5435	-
RabbitMQ	5672	15672

🎯 Features

Forum Service

• Create, read, update, and delete questions
• Create, read, update, and delete answers
• Mark best answer for questions
• Filter questions by author
• Attachment management
• Student and Instructor roles
• Pagination support

User Service

• User registration
• User authentication with JWT tokens
• Role-based authorization
• Password management
• Email validation
• Token refresh mechanism

Notification Service

• Send notifications to users
• Read notification status
• Integration with other services via events
• Notification history

📂 Project Structure

Forum/
├── src/
│   ├── BuildingBlocks/          # Shared library
│   │   ├── Base/                # Domain base classes
│   │   ├── Exceptions/          # Custom exceptions
│   │   ├── Extensions/          # Helper extensions
│   │   ├── Logging/             # Logging infrastructure
│   │   ├── Messaging/           # Event bus implementation
│   │   └── Middleware/          # Common middleware
│   ├── Forum/                   # Forum microservice
│   │   ├── Application/         # Application layer
│   │   ├── Domain/              # Domain layer
│   │   ├── Endpoints/           # API endpoints
│   │   ├── Infrastructure/      # Infrastructure layer
│   │   └── Migrations/          # Database migrations
│   ├── Notification/            # Notification microservice
│   │   ├── Application/
│   │   ├── Domain/
│   │   ├── Endpoints/
│   │   ├── Infrastructure/
│   │   └── Migrations/
│   └── User/                    # User microservice
│       ├── Data/                # Data layer
│       ├── DTOs/                # Data transfer objects
│       ├── Endpoints/           # API endpoints
│       ├── Extensions/          # Extensions
│       ├── Migrations/          # Database migrations
│       └── Services/            # Business services
├── tests/
│   ├── Forum.UnitTest/          # Forum unit tests
│   ├── Notification.UnitTest/   # Notification unit tests
│   ├── User.UnitTest/           # User unit tests
│   └── Seed/                    # Database seeding
├── docs/                        # Documentation
├── compose.yaml                 # Docker Compose configuration
└── Forum.sln                    # Solution file

🚦 Getting Started

Prerequisites

• .NET 10.0 SDK
• Docker and Docker Compose
• PostgreSQL (if running locally without Docker)
• RabbitMQ (if running locally without Docker)

Running with Docker Compose

1. Clone the repository:

git clone <repository-url>
cd Forum

2. Option A - Run Everything in Docker (Recommended)

# Start all services (APIs + Databases + RabbitMQ)
docker-compose up -d

# Access the APIs:
# Forum API:        http://localhost:8000/swagger
# Notification API: http://localhost:8001/swagger
# User API:         http://localhost:8002/swagger

# HTTPS is also available:
# Forum API:        https://localhost:8443/swagger
# Notification API: https://localhost:8444/swagger
# User API:         https://localhost:8445/swagger

3. Option B - Run APIs Locally (For Debugging)

# Start only infrastructure (databases and RabbitMQ)
docker-compose up -d userdb forumdb notificationdb messagebroker

# Terminal 1 - Forum Service
cd src/Forum
dotnet run

# Terminal 2 - User Service
cd src/User
dotnet run

# Terminal 3 - Notification Service
cd src/Notification
dotnet run

# Access the APIs:
# Forum API:        http://localhost:5000/swagger
# Notification API: http://localhost:5001/swagger
# User API:         http://localhost:5002/swagger

HTTPS Certificates in Docker

HTTPS certificates are automatically generated inside containers on first startup. No manual configuration needed!

Database Migrations

Migrations run automatically when starting services. To run manually:

# Forum Service
cd src/Forum
dotnet ef database update

# User Service
cd src/User
dotnet ef database update

# Notification Service
cd src/Notification
dotnet ef database update

📖 API Documentation

Local Development

• Forum API: http://localhost:5000/swagger
• User API: http://localhost:5002/swagger
• Notification API: http://localhost:5001/swagger

Docker Environment

HTTP:

• Forum API: http://localhost:8000/swagger
• User API: http://localhost:8002/swagger
• Notification API: http://localhost:8001/swagger

HTTPS:

• Forum API: https://localhost:8443/swagger
• User API: https://localhost:8445/swagger
• Notification API: https://localhost:8444/swagger

RabbitMQ Management

• URL: http://localhost:15672
• Username: guest
• Password: guest

🧪 Testing

Run all tests:

dotnet test

Run tests for a specific project:

dotnet test tests/Forum.UnitTest
dotnet test tests/User.UnitTest
dotnet test tests/Notification.UnitTest

🔧 Configuration

Each service can be configured via appsettings.json and appsettings.Development.json. Key configurations include:

• Connection Strings: Database connections
• JWT Settings: Token configuration (User service)
• RabbitMQ Settings: Message broker configuration
• Logging Levels: Serilog configuration
• CORS Policies: Cross-origin resource sharing

📝 Domain Models

Forum Service

• Question: Forum questions with title, content, and metadata
• Answer: Responses to questions
• Attachment: File attachments for questions/answers
• Student: Student user type
• Instructor: Instructor user type with additional privileges

User Service

• ApplicationUser: Extended Identity user
• Roles: Role-based access control

Notification Service

• Notification: User notifications with read status

🔄 Event-Driven Communication

The system uses an event bus pattern for inter-service communication:

• Domain Events: Events within a single service boundary
• Integration Events: Events that cross service boundaries
• Event Handlers: Process events asynchronously

Supported event bus implementations:

• InMemoryEventBus: For development and testing
• RabbitMQEventBus: For production use

🛡️ Error Handling

The application implements comprehensive error handling with:

• Custom Exception Types: BadRequest, NotFound, Validation, Forbidden, InternalServer
• Global Exception Handler: Centralized exception processing
• Result Pattern: Functional error handling for operations
• Structured Logging: All errors are logged with context

🐳 Docker

Quick Commands

# Start everything
docker-compose up -d

# View logs
docker-compose logs -f

# View specific service logs
docker-compose logs -f forum
docker-compose logs -f notification
docker-compose logs -f user

# Check status
docker-compose ps

# Stop everything
docker-compose down

# Stop and remove volumes (clean slate)
docker-compose down -v

# Restart a specific service
docker-compose restart forum

Docker Features

✅ Automatic HTTPS Certificates - Generated automatically inside containers
✅ Safe Ports - Uses browser-safe ports (8000-8002, 8443-8445)
✅ Health Checks - All services have health monitoring
✅ Persistent Data - Databases use volumes for data persistence
✅ Auto-restart - Services restart automatically on failure
✅ Zero Configuration - Just run docker-compose up -d

Architecture Overview

┌─────────────────────────────────────────────────────────────┐
│                        Host Machine                         │
│                                                             │
│  Browser → :8000 (Forum HTTP)    → :8443 (Forum HTTPS)     │
│         → :8001 (Notification)   → :8444 (Notification)     │
│         → :8002 (User)          → :8445 (User)             │
│         → :15672 (RabbitMQ UI)                             │
│                                                             │
│  ┌──────────────────────────────────────────────────────┐  │
│  │              Docker Network                          │  │
│  │                                                      │  │
│  │  ┏━━━━━━━━━━┓  ┏━━━━━━━━━━━━━┓  ┏━━━━━━━━━━┓       │  │
│  │  ┃ Forum    ┃  ┃ Notification┃  ┃  User    ┃       │  │
│  │  ┃   API    ┃  ┃     API     ┃  ┃   API    ┃       │  │
│  │  ┗━━━━━━━━━━┛  ┗━━━━━━━━━━━━━┛  ┗━━━━━━━━━━┛       │  │
│  │       ↓              ↓                ↓              │  │
│  │  ┌────────┐    ┌────────┐      ┌────────┐          │  │
│  │  │ForumDB │    │NotifyDB│      │UserDB  │          │  │
│  │  └────────┘    └────────┘      └────────┘          │  │
│  │       ↓              ↓                ↓              │  │
│  │            ┌───────────────────┐                     │  │
│  │            │    RabbitMQ       │                     │  │
│  │            └───────────────────┘                     │  │
│  └──────────────────────────────────────────────────────┘  │
└─────────────────────────────────────────────────────────────┘

Troubleshooting

APIs not responding?

# Check if containers are running
docker-compose ps

# Check logs for errors
docker-compose logs -f

Database connection issues?

# Restart databases
docker-compose restart forumdb notificationdb userdb

RabbitMQ issues?

# Restart RabbitMQ
docker-compose restart messagebroker

Clean everything and start fresh?

docker-compose down -v
docker-compose up -d --build

🤝 Contributing

1. Fork the repository
2. Create a feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add some amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

🙏 Acknowledgments

• Built with .NET 10.0
• Inspired by Clean Architecture and DDD principles
• Microservices architecture patterns