Load Balancer

To create a load balancer program in Go, follow these steps:

Step 1: Initialize the Go Module

First, create a new directory for your project and initialize the Go module.

mkdir loadbalancer
cd loadbalancer
go mod init github.com/username/loadbalancer

Step 2: Install Dependencies

You will need the gorilla/mux library for routing.

go get github.com/gorilla/mux

Step 3: Create the `loadbalancer.go` File

Create a lib/loadbalancer.go file to handle the load balancer functionality.

// loadbalancer.go
package lib

import (
	"fmt"
	"log"
	"net/http"
	"net/http/httputil"
	"net/url"
	"sync/atomic"
)

type ServerPool struct {
	servers []*url.URL
	current uint64
}

func (p *ServerPool) AddServer(server *url.URL) {
	p.servers = append(p.servers, server)
}

func (p *ServerPool) NextServer() *url.URL {
	next := atomic.AddUint64(&p.current, uint64(1))
	return p.servers[next%uint64(len(p.servers))]
}

func (p *ServerPool) LoadBalance(w http.ResponseWriter, r *http.Request) {
	server := p.NextServer()
	proxy := httputil.NewSingleHostReverseProxy(server)
	proxy.ServeHTTP(w, r)
}

var pool ServerPool

func Run() {
	servers := []string{
		"http://localhost:8081",
		"http://localhost:8082",
		"http://localhost:8083",
	}

	for _, server := range servers {
		url, err := url.Parse(server)
		if err != nil {
			log.Fatalf("Failed to parse server URL: %v", err)
		}
		pool.AddServer(url)
	}

	http.HandleFunc("/", pool.LoadBalance)
	fmt.Println("Load balancer started on :8080")
	log.Fatal(http.ListenAndServe(":8080", nil))
}

Step 4: Create the `main.go` File

Create a main.go file to start the load balancer.

// main.go
package main

import "github.com/username/loadbalancer/lib"

func main() {
	lib.Run()
}

Step 5: Run the Program

Run the program using the go run command.

go run main.go

This will start the load balancer on port 8080, balancing requests across the servers specified in the servers slice.

Last modified: 08 January 2025