Load balancing between workers in Node.js - Mini Project: Build & Apply

Load balancing between workers

📖 Scenario: You are building a simple Node.js server that uses multiple worker processes to handle requests efficiently. To share the work fairly, you want to balance the load between these workers.

🎯 Goal: Create a Node.js script that sets up a cluster with 3 worker processes and distributes incoming requests evenly using a round-robin load balancing approach.

📋 What You'll Learn

Create a cluster with exactly 3 worker processes

Use a variable to keep track of the current worker index

Implement a function to select the next worker in round-robin order

Assign incoming requests to workers using the round-robin function

💡 Why This Matters

🌍 Real World

Load balancing between workers helps servers handle many requests efficiently by sharing work fairly.

💼 Career

Understanding Node.js clustering and load balancing is important for backend developers building scalable web servers.

1

Create the cluster and workers

Write code to import the cluster and http modules, and create exactly 3 worker processes using cluster.fork(). Store the workers in an array called workers.

Node.js

# Your code here to import modules and create 3 workers stored in workers array

Need a hint?

Use cluster.fork() inside a for loop to create 3 workers and store them in an array named workers.

2

Add a variable to track the current worker index

Add a variable called currentWorkerIndex and set it to 0. This will help track which worker should get the next request.

Node.js

const cluster = require('cluster');
const http = require('http');

if (cluster.isMaster) {
    const workers = [];
    for (let i = 0; i < 3; i++) {
        const worker = cluster.fork();
        workers.push(worker);
    }
    // Add currentWorkerIndex variable here
    # Your code here

Need a hint?

Declare let currentWorkerIndex = 0; inside the if (cluster.isMaster) block.

3

Create a function to select the next worker in round-robin

Write a function called getNextWorker that returns the next worker from the workers array using currentWorkerIndex. After returning, it should update currentWorkerIndex to the next position, wrapping back to 0 after reaching the last worker.

Node.js

const cluster = require('cluster');
const http = require('http');

if (cluster.isMaster) {
    const workers = [];
    for (let i = 0; i < 3; i++) {
        const worker = cluster.fork();
        workers.push(worker);
    }
    let currentWorkerIndex = 0;

    // Write getNextWorker function here
    # Your code here

Need a hint?

Use modulo % to wrap currentWorkerIndex back to 0 after reaching the last worker.

4

Assign incoming requests to workers using round-robin

Create an HTTP server that listens on port 8000. For each incoming request, use getNextWorker() to select a worker and send the request to that worker using worker.send().

Node.js

const cluster = require('cluster');
const http = require('http');

if (cluster.isMaster) {
    const workers = [];
    for (let i = 0; i < 3; i++) {
        const worker = cluster.fork();
        workers.push(worker);
    }
    let currentWorkerIndex = 0;

    function getNextWorker() {
        const worker = workers[currentWorkerIndex];
        currentWorkerIndex = (currentWorkerIndex + 1) % workers.length;
        return worker;
    }

    // Create HTTP server and assign requests to workers
    # Your code here
}

Need a hint?

Create the server with http.createServer. Inside the request handler, call getNextWorker() and send a message to the worker. Then respond to the client.