Chatroom with Golang and NATS

A scalable real-time chat application built with Go, NATS messaging system, Redis for state management, and WebSocket for client communication.

🚀 Features

• Real-time messaging with WebSocket support
• Room-based chat functionality with presence tracking
• Distributed message broadcasting via NATS pub/sub
• Persistent state management with Redis
• Horizontally scalable architecture
• Docker-ready deployment
• Development environment with hot-reload
• Comprehensive test coverage

Project Structure

.
├── .air.toml.example           # Air configuration template for hot-reload
├── .gitignore                  # Git ignore rules
├── config.json.example         # Example configuration file
├── config_test.json.example    # Example test configuration
├── docker-compose.yml          # Production Docker composition
├── docker-compose-dev.yml      # Development Docker composition
├── Dockerfile                  # Multi-stage Docker build file
├── go.mod                      # Go module dependencies
├── go.sum                      # Go module checksums
|
├── api/
│   └── ws/
│       ├── handler.go          # WebSocket connection and message handling
│       └── setup.go            # WebSocket route configuration
├── cmd/
│   ├── client/
│   │   └── main.go            # CLI chat client implementation
│   └── server/
│   │   └── main.go            # Chat server entry point
├── config/
│   ├── read.go                # Configuration file reader
│   └── type.go                # Configuration type definitions
├── internal/
│   ├── app/
│   │   └── server.go          # Core application setup and lifecycle
│   ├── domain/
│   │   └── chat.go            # Chat domain types and constants
│   ├── nats/
│   │   ├── nats_client.go     # NATS client implementation
│   │   ├── publisher.go       # NATS message publishing
│   │   └── subscriber.go      # NATS subscription handling
│   └── redis/
│       └── redis_client.go    # Redis client implementation
├── pkg/
│   └── logger/
│       └── logger.go          # Structured logging package using zap
├── service/
│   └── chat_service.go        # Chat business logic implementation
└── test/
    ├── integration/
    │   └── websocket_integration_test.go  # WebSocket integration tests
    └── unit/
        ├── chat_service_test.go    # Chat service unit tests
        ├── nats_client_test.go     # NATS client unit tests
        └── redis_client_test.go    # Redis client unit tests

🏗 Architecture

The application follows clean architecture principles:

API Layer (api/ws)

• WebSocket Handler (handler.go)

  • Manages real-time WebSocket connections and client sessions
  • Handles connection lifecycle (connect, disconnect, ping/pong)
  • Validates incoming messages and routes to appropriate service methods
  • Maintains client state and room membership

• WebSocket Setup (setup.go)

  • Configures WebSocket routes and middleware
  • Initializes WebSocket upgrader with security settings
  • Sets up connection parameters and timeouts

Service Layer (service/chat_service.go)

• Chat Service
  • Core business logic implementation
  • Manages user sessions and room state
  • Handles message broadcasting and delivery
  • Implements chat commands (/join, /leave, /users, etc.)
  • Coordinates between WebSocket, NATS, and Redis layers

Domain Layer (internal/domain)

• Chat Domain (chat.go)
  • Defines core domain models and types
  • Contains business rules and validation logic
  • Implements chat room and user entities
  • Defines message types and formats

Infrastructure Layer

• NATS Integration (internal/nats)
  • Publisher: Distributes messages across server instances
  • Subscriber: Handles incoming messages from other instances
  • Manages pub/sub channels for room-based communication
• Redis Integration (internal/redis)
  • Maintains persistent state (user sessions, room info)
  • Handles distributed presence tracking
  • Manages user-room mappings and message history
• Logging (pkg/logger)
  • Structured logging using zap
  • Different log levels for development/production
  • Log file and console output support

Application Core (internal/app)

• Server (server.go)
  • Application lifecycle management
  • Component initialization and dependency injection
  • Configuration management
  • Service orchestration

Testing (test)

• Integration Tests
  • WebSocket communication testing
  • End-to-end functionality verification
  • Service integration validation
• Unit Tests
  • Individual component testing
  • Business logic validation
  • Mock-based dependency testing

Configuration (config)

• Configuration file parsing and validation
• Environment-specific settings
• Runtime configuration management

This architecture enables:

• Horizontal scalability through NATS pub/sub
• High availability with Redis state management
• Clear separation of concerns
• Easy testing and maintenance
• Flexible deployment options (local/Docker)

🛠 Setup & Development

Prerequisites

• Go 1.23+
• Docker & Docker Compose

Configuration

The application uses different configuration files depending on your setup:

1. Docker Deployment

# Copy the example config
cp config.json.example config.json

# Edit config.json to use container hostnames:
{
  "port": 8080,
  "nats_url": "nats://nats:4222",    # Use container hostname
  "redis_url": "redis://redis:6379",  # Use container hostname
  "log_level": "debug",
  "log_file": "server.log"
}

# Start the application
docker compose up -d --build

2. Local Development

# Copy and edit config for local development
cp config.json.example config.json

# Edit config.json to use localhost:
{
  "port": 8080,
  "nats_url": "nats://localhost:4222",  # Use localhost with exposed ports
  "redis_url": "redis://localhost:6379", # Use localhost with exposed ports
  "log_level": "debug",
  "log_file": "server.log"
}

# Start dependencies
docker compose up nats redis -d

# Run the server locally
go run cmd/server/main.go --config config.json

3. Development with Hot-Reload

# Copy configs
cp config.json.example config.json
cp .air.toml.example .air.toml

# Edit config.json as shown above for Docker setup
# Start development environment
docker compose -f docker-compose-dev.yml up --build

CLI

Running the Client

# Run the client with default server address (localhost:8080)
go run cmd/client/main.go

# Run the client with custom server address
go run cmd/client/main.go -addr server.example.com:8080

Command	Description
/help	Show help message and available commands
/users	List all active users in the system
/users <room>	List users in a specific room
/rooms	List all active chat rooms
/join <room>	Join or switch to a specific room
/leave	Leave current room and return to global chat

Usage Examples

# Start chatting in global room
> Hello everyone!

# Join a specific room
> /join development
[System] Joined room: development

# List room members
> /users development
[System] Users in development: alice, bob

# List all members
> /users
[System] Users: alice, bob, charlie

# Send message in current room
> Hey team!
[Sent to development] Hey team!

# Return to global chat
> /leave
[System] Returned to global chat

Notes

• New users automatically join the 'global' chat room
• Messages are only visible to users in the same room
• Room names are case-sensitive and can't have spaces
• Username is requested when starting the client

Testing

# make config for test
cp config_test.json.example config_test.json

# Run all tests
go test -p 1 ./test/...

# Run unit tests
go test ./test/unit/...

# Run integration tests
go test ./test/integration/...

Monitoring

Access logs through Dozzle at http://localhost:9999
NATS monitoring at http://localhost:8222
Redis Commander at http://localhost:8001 (dev environment)

Note: Dozzle is a lightweight container log viewer that tails our server_logs container output. It provides SQL-like analytics capabilities to query through logs, making it great for development. However, for production environments, it's recommended to use more robust solutions like:

• ELK Stack (Elasticsearch, Logstash, Kibana)
• Grafana + Promtail + Loki
• Prometheus + Grafana These solutions offer better scalability, retention policies, alerting, and production-grade monitoring capabilities.

🔮 Future Improvements

Architecture & Design

• Migrate to Hexagonal/Clean Architecture or Domain-Driven Design (DDD)
  • Better separation of domain logic from infrastructure
  • More explicit bounded contexts
  • Improved testability and maintainability
• Implement Event-Driven Architecture
  • Better handling of distributed events
  • Improved system scalability
  • Loose coupling between components

Infrastructure

• Enhanced Redis State Management
  • Implement state recovery mechanisms
  • Add data persistence strategies
  • Improve distributed state synchronization
  • Add cache eviction policies
• Message Queue Implementation
  • Traffic buffering
  • Message persistence for reliability
• Enhanced Load Balancing
  • Smart routing based on room capacity
  • Geographic distribution of servers

Features

• Extended Chat Capabilities
  • Message history
  • File sharing (Using Minio)
  • User authentication
  • Private messaging
• Enhanced Monitoring
  • Custom metrics
  • Distributed tracing
  • OpenTelemetry integration
  • End-to-end request tracking
  • Performance analytics
• Enhanced Security Measures
  • Rate limiting
  • Input validation
  • Message encryption
  • Security headers
  • CORS policy refinement

These improvements would enhance the system's reliability, maintainability, and scalability while providing a better user experience.

📝 License

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

👤 Author

Sepehr Ghafari - GitHub