Creating worker threads in Node.js - Try It Yourself

Creating worker threads

📖 Scenario: You are building a Node.js application that needs to perform a heavy calculation without blocking the main program. To do this, you will use worker threads to run the calculation in the background.

🎯 Goal: Create a simple Node.js program that uses the worker_threads module to run a worker thread which calculates the sum of numbers from 1 to 1000000 and sends the result back to the main thread.

📋 What You'll Learn

Create a worker thread using the Worker class from the worker_threads module

Send a message from the main thread to the worker thread

Perform the sum calculation inside the worker thread

Send the result back from the worker thread to the main thread

💡 Why This Matters

🌍 Real World

Worker threads help Node.js applications perform CPU-heavy tasks without freezing the user interface or blocking other operations.

💼 Career

Understanding worker threads is important for backend developers to build scalable and responsive Node.js applications that handle intensive computations efficiently.

1

Import the worker_threads module and check if current thread is main

Write code to import Worker and isMainThread from the worker_threads module. Then create an if statement that checks if isMainThread is true.

Node.js

const { Worker, isMainThread } = require('worker_threads');

// Your code here

Need a hint?

Use require('worker_threads') to import Worker and isMainThread. Then write if (isMainThread) { ... } else { ... } to separate main and worker code.

2

Create a new Worker instance in the main thread

Inside the if (isMainThread) block, create a new Worker instance that runs the current file using __filename. Assign it to a variable called worker.

Node.js

const { Worker, isMainThread } = require('worker_threads');

if (isMainThread) {
    const worker = new Worker(__filename);
    // Your code here
} else {
    // Worker thread code will go here
}

Need a hint?

Create a Worker with new Worker(__filename) inside the main thread block.

3

Send a message from main thread and calculate sum in worker thread

In the main thread block, send a message { start: 1, end: 1000000 } to the worker using worker.postMessage(). In the else block (worker thread), listen for messages using parentPort.on('message', (data) => { ... }). Inside the listener, calculate the sum of numbers from data.start to data.end and send the result back using parentPort.postMessage(sum).

Node.js

const { Worker, isMainThread, parentPort } = require('worker_threads');

if (isMainThread) {
    const worker = new Worker(__filename);
    worker.postMessage({ start: 1, end: 1000000 });
    // Your code here
} else {
    parentPort.on('message', (data) => {
        // Your code here
    });
}

Need a hint?

Use worker.postMessage() in main thread to send data. In worker thread, use parentPort.on('message', ...) to receive data and calculate sum with a for loop. Then send result back with parentPort.postMessage().

4

Receive and handle the result in the main thread

In the main thread block, add a listener for worker.on('message', (result) => { ... }) to receive the sum result from the worker. Inside the listener, assign the received result to a variable called totalSum.

Node.js

const { Worker, isMainThread, parentPort } = require('worker_threads');

if (isMainThread) {
    const worker = new Worker(__filename);
    worker.postMessage({ start: 1, end: 1000000 });
    worker.on('message', (result) => {
        // Your code here
    });
} else {
    parentPort.on('message', (data) => {
        let sum = 0;
        for (let i = data.start; i <= data.end; i++) {
            sum += i;
        }
        parentPort.postMessage(sum);
    });
}

Need a hint?

Use worker.on('message', (result) => { ... }) in main thread to get the result and assign it to totalSum.