CPU profiling basics in Node.js - Mini Project: Build & Apply

CPU Profiling Basics in Node.js

📖 Scenario: You are working on a Node.js application that sometimes runs slowly. To find out which parts of your code use the most CPU time, you want to create a CPU profile. This helps you understand where your program spends time, so you can improve it.

🎯 Goal: Build a simple Node.js script that uses the built-in inspector module to start and stop CPU profiling, then save the profile data to a file.

📋 What You'll Learn

Create a Node.js script that imports the inspector module

Start a CPU profile using the inspector session

Run a sample CPU-intensive function

Stop the CPU profile and save the profile data to a file named profile.cpuprofile

💡 Why This Matters

🌍 Real World

CPU profiling helps developers find performance bottlenecks in Node.js applications, improving speed and user experience.

💼 Career

Knowing how to profile CPU usage is valuable for backend developers, performance engineers, and anyone optimizing Node.js services.

1

Set up the inspector session

Create a variable called inspector that imports the inspector module, and create a new inspector.Session() instance called session. Then call session.connect() to start the session.

Node.js

const inspector = require('inspector');
const session = new inspector.Session();
// Your code here

Need a hint?

Use require('inspector') to import the module, then create a new session with new inspector.Session(). Don't forget to call session.connect() to start the session.

2

Start the CPU profiler

Use session.post to start the CPU profiler by calling session.post('Profiler.enable') and then session.post('Profiler.start').

Node.js

const inspector = require('inspector');
const session = new inspector.Session();
session.connect();
// Your code here

Need a hint?

Call session.post('Profiler.enable') first to enable profiling, then session.post('Profiler.start') to begin CPU profiling.

3

Run a CPU-intensive function

Create a function called calculate that runs a loop from 0 to 999999 and sums the numbers. Then call calculate() to simulate CPU work.

Node.js

const inspector = require('inspector');
const session = new inspector.Session();
session.connect();
session.post('Profiler.enable');
session.post('Profiler.start');
// Your code here

Need a hint?

Write a function named calculate that sums numbers in a loop. Call it once to create CPU load.

4

Stop profiling and save the profile

Use session.post('Profiler.stop') with a callback that receives the profile data. Inside the callback, write the profile data to a file named profile.cpuprofile using require('fs').writeFileSync. Then call session.disconnect().

Node.js

const inspector = require('inspector');
const session = new inspector.Session();
session.connect();
session.post('Profiler.enable');
session.post('Profiler.start');

function calculate() {
    let sum = 0;
    for (let i = 0; i < 1000000; i++) {
        sum += i;
    }
    return sum;
}

calculate();
// Your code here

Need a hint?

Stop the profiler with session.post('Profiler.stop'). Use the callback to get the profile data and save it to a file with fs.writeFileSync. Finally, disconnect the session.