Master and worker processes in Node.js - Mini Project: Build & Apply

Master and Worker Processes in Node.js

📖 Scenario: You are building a simple Node.js application that uses multiple processes to handle tasks efficiently. The main process (master) will create worker processes to perform work in parallel.

🎯 Goal: Create a Node.js script that sets up a master process and two worker processes using the cluster module. The master will send a message to each worker, and each worker will respond back.

📋 What You'll Learn

Use the cluster module to create worker processes

Create exactly two worker processes

Master process sends a message to each worker

Each worker sends a message back to the master

Use process.on('message') to handle messages

💡 Why This Matters

🌍 Real World

Using master and worker processes helps build fast and scalable Node.js servers that can handle many tasks at once by using multiple CPU cores.

💼 Career

Understanding process management and inter-process communication is important for backend developers working with Node.js in production environments.

1

Setup the cluster module and check if current process is master

Write code to import the cluster module and the os module. Then create a condition that checks if cluster.isMaster is true.

Node.js

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

// Check if current process is master
if (cluster.isMaster) {
  // Your code here
}

Need a hint?

Use require('cluster') and require('os'). Then check cluster.isMaster to know if the current process is the master.

2

Create two worker processes inside the master block

Inside the if (cluster.isMaster) block, write code to create exactly two worker processes using cluster.fork() twice.

Node.js

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

if (cluster.isMaster) {
  // Create two worker processes
  // Your code here
}

Need a hint?

Call cluster.fork() two times inside the master block to create two workers.

3

Send a message from master to each worker and listen for messages from workers

Inside the if (cluster.isMaster) block, add a for loop that iterates over Object.values(cluster.workers). For each worker, send a message { cmd: 'start' } using worker.send(). Also, add a listener on each worker for 'message' events that logs the received message with console.log.

Node.js

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

if (cluster.isMaster) {
  cluster.fork();
  cluster.fork();

  // Send message to each worker and listen for messages
  // Your code here
}

Need a hint?

Use Object.values(cluster.workers) to get all workers. Send a message with worker.send() and listen with worker.on('message').

4

Add worker process code to receive message and reply to master

Outside the if (cluster.isMaster) block, write code for the worker processes. Use process.on('message') to listen for messages. When a message with cmd === 'start' is received, send back a message to the master with process.send({ reply: 'Worker is ready' }).

Node.js

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

if (cluster.isMaster) {
  cluster.fork();
  cluster.fork();

  for (const worker of Object.values(cluster.workers)) {
    worker.send({ cmd: 'start' });
    worker.on('message', (msg) => {
      console.log(`Master received: ${msg.reply}`);
    });
  }
}

// Worker process code
// Your code here

Need a hint?

Use else for worker code. Listen with process.on('message') and reply with process.send().