HTTP Load Balancer in Go

A Layer 7 (HTTP) load balancer implementation that distributes incoming HTTP requests across multiple backend servers. Features include round-robin load balancing, health checks, and dynamic backend management.

Features

• ✨ Layer 7 (HTTP) Load Balancing
• 🔄 Round Robin Algorithm
• 💓 Active Health Checks
• 🚦 Dynamic Backend Management
• 🎮 Control Interface for Backend States
• 📊 Request Distribution Logging

Project Structure

load-balancer/
├── cmd/                    # Command-line applications
│   ├── control/           # Backend control tool
│   ├── test-client/       # Load testing client
│   └── server/            # Main load balancer server
├── internal/              # Private application code
│   ├── core/             # Core business logic
│   │   ├── backend/      # Backend server management
│   │   │   ├── backend.go    # Backend interface and implementation
│   │   │   └── test_backend.go # Test backend for development
│   │   └── balancer/     # Load balancing logic
│   └── utils/            # Shared utilities
│       └── logger/       # Colored logging package
└── README.md

Package Descriptions

• cmd/server: Main application that starts the load balancer and test backends

• cmd/control: Tool to control backend states (failure simulation, delays)

• cmd/test-client: Tool to generate test traffic

• internal/core/backend: Backend server management

  • Handles both real and test backend implementations
  • Manages health checks and server states
  • Implements proxy forwarding

• internal/core/balancer: Load balancing logic

  • Implements round-robin selection
  • Manages backend pool
  • Handles request distribution

• internal/utils/logger: Shared logging utilities

  • Color-coded log output
  • Different log levels for different operations
  • Clear distinction between health checks and client requests

Getting Started

Prerequisites

• Go 1.24 or higher

Running the Load Balancer

1. Start the load balancer with test backends:

go run cmd/server/main.go

This will start:

• Load balancer on port 8080
• Three test backends on ports 8081, 8082, and 8083

2. Control backend states (in another terminal):

# Make a backend fail
go run cmd/control/main.go -port 8081 -fail=true

# Add delay to a backend
go run cmd/control/main.go -port 8082 -delay=1s

# Recover a failed backend
go run cmd/control/main.go -port 8081 -fail=false

3. Test with sample traffic (in another terminal):

# Send 10 requests, 3 at a time
go run cmd/test-client/main.go -n 10 -c 3

# Rapid-fire test with 100 requests
go run cmd/test-client/main.go -n 100 -c 10 -i 10ms

How It Works

1. Load Balancing:

   • Round-robin algorithm distributes requests
   • Only healthy backends receive traffic
   • Dynamic backend pool management

2. Health Checks:

   • Regular health checks every 2 seconds
   • Automatic backend removal on failure
   • Automatic recovery when backend is healthy

3. Request Flow:

   Client → Load Balancer → Backend Selection → Health Check → Forward Request
                                            ↳ Error if no healthy backends
   

4. Logging:

   • Color-coded for different operations:
     • 🟢 Green: Successful health checks
     • 🔴 Red: Failed health checks
     • 🔵 Blue: Client requests
     • 🟡 Yellow: Load balancer operations

Development

To add new features or modify existing ones:

1. Clone the repository:

git clone https://github.com/DevBajaj02/load-balancer.git
cd load-balancer

2. Install dependencies:

go mod tidy

3. Make changes and test:

go run cmd/server/main.go

Contributing

This is a project created for learning purposes by @DevBajaj02. Feedback is welcome to improve the project!