fanout-subscription

A simple fan-out subscription service implemented in Go that demonstrates:

• TCP server accepting multiple client connections, by default on port 8080
• HTTP endpoint to trigger mock event sending, by default on port 8081
• Broadcasting events to all connected clients
• Client state management and deduplication
• Thread-safe concurrent operations

Architecture

The service consists of:

• Server: Manages client connections and broadcasts events
• Client: Maintains connection and handles incoming events
• Event: Data structure for messages passed through the system

Usage

Install dependencies:

go mod tidy

Start the server:

go run cmd/main.go

Before production

Before deploying this to production, we might want to:

Features

• Add endpoint to post a proper message with configurable body
• Make max number of clients configurable, use connection pool

Robustness

• Put in proper error handling, gracefully handle errors and panics
• Make clients automatically reconnect when they drop (ie with exponential backoff timing)
• Handle clients joining and leaving with separate endpoints

Scalability

• Add a message queue (RabbitMQ or Kafka) so we don't lose messages when clients are offline (if message volume is high)
• Add rate limiting so that no single client can use up all the resources

Security

• Add proper auth
• Use TLS/SSL

Monitoring

• Add proper logging
• Use metrics (Prometheus + Grafana)
• Add health checks for the server
• Set up alerts

Testing

• Write some unit tests
• Add integration tests for Db and message queue if we use them