HTTP Round Robin Load Balancer

A high-performance Round Robin load balancer and API server implementation in Go, with health checks, graceful shutdown, and unit testing.

Features

• Round Robin load balancing with health checking
• Multiple backend support with automatic failover
• Health monitoring with configurable check intervals
• Graceful shutdown handling
• Docker support for easy testing
• Test coverage
• JSON echo API server implementation

Architecture

The project consists of two main components:

Load Balancer

• Distributes incoming requests across multiple backends using Round Robin algorithm
• Monitors backend health and removes unhealthy instances from rotation
• Provides automatic failover when backends become unavailable
• Implements graceful shutdown with configurable timeout

Echo API Server

• Accepts POST requests with JSON payloads
• Validates incoming JSON content
• Returns exact copy of received JSON payload
• Includes health check endpoint (/healthz)
• Supports multiple concurrent instances

Getting Started

Prerequisites

• Go 1.23 or higher
• Docker and Docker Compose (optional)

Running with Docker Compose

The easiest way to run the complete setup is using Docker Compose:

docker-compose up

This will start:

• 3 API server instances (ports 8081-8083)
• 1 Load balancer instance (port 8080)

Running Manually

1. Start multiple API servers:

make start-backends

2. Start the load balancer:

make start-loadbalancer

To stop all services:

make stop-all

Testing the Setup

1. Send a test request through the load balancer:

curl -X POST -H "Content-Type: application/json" \
-d '{"game":"Mobile Legends", "gamerID":"GYUTDTE", "points":20}' \
http://localhost:8080

2. Check health endpoint:

curl http://localhost:8080/healthz

Configuration

Load Balancer Configuration

• port: Port to listen on (default: 8080, configurable via command line flag)
• BACKEND_SERVERS: Comma-separated list of backend URLs (must be set as an environment variable)

API Server Configuration

• port: Port to listen on (configurable via command line flag)

Testing

Run the test suite:

go test ./...

The tests cover:

• Round Robin logic
• Backend health checking
• Failover scenarios
• API server functionality
• Load balancer behavior

Future Improvements

Potential enhancements that could be added:

1. Metrics collection so we can use tools such as Prometheus
2. Circuit breaker implementation to handle failing backends
3. Weighted round robin support
4. TLS support
5. Dynamic backend registration/removal
6. More advanced health checks, now it always returns a HTTP OK 200 response