Skip to main content

How can you debug memory leaks in a Node.js app?

Debugging memory leaks in a Node.js application involves identifying code that retains memory unnecessarily, leading to increased memory usage over time. Here’s a step-by-step approach to effectively diagnose and fix memory leaks:

How can you debug memory leaks in a Node.js app?

1. Monitor Memory Usage

Use built-in tools to observe memory trends:

node --inspect app.js

Or:

setInterval(() => {
  console.log(process.memoryUsage());
}, 5000);

Look for increasing heapUsed or rss (resident set size) over time.

2. Use Chrome DevTools

  1. Start your app with the --inspect flag:

    node --inspect-brk app.js

  2. Open Chrome and go to chrome://inspect.

  3. Take Heap Snapshots before and after the suspected leak timeframe.

  4. Compare snapshots to find objects that persist unexpectedly.

3. Use Heapdump

Install and trigger a heap snapshot programmatically:

npm install heapdump
const heapdump = require('heapdump');
heapdump.writeSnapshot('/path/to/snapshot.heapsnapshot');

Analyze the snapshot using Chrome DevTools.

4. Track Down Retained Objects

Look for:

  • Event listeners that are never removed (EventEmitter leaks).

  • Closures that capture and retain variables.

  • Caches that grow unbounded.

  • Global variables or static references holding data too long.

5. Tools for Leak Detection

  • clinic.js (clinic doctor): Detects performance and memory issues.

  • memwatch-next: Tracks memory usage and detects leaks.

  • v8-profiler-node8: For more advanced profiling.

6. Best Practices to Prevent Leaks

  • Always remove listeners: emitter.removeListener()

  • Avoid global variables unless necessary.

  • Use weak references for caches if possible (WeakMap, WeakSet).

  • Watch for circular references in closures or objects.

Popular posts from this blog

Explain the Angular compilation process: View Engine vs. Ivy.

 The Angular compilation process transforms your Angular templates and components into efficient JavaScript code that the browser can execute. Over time, Angular has evolved from the View Engine compiler to a newer, more efficient system called Ivy . Here's a breakdown of the differences between View Engine and Ivy , and how each affects the compilation process: 🔧 1. What Is Angular Compilation? Angular templates ( HTML inside components) are not regular HTML—they include Angular-specific syntax like *ngIf , {{ }} interpolation, and custom directives. The compiler translates these templates into JavaScript instructions that render and update the DOM. Angular uses Ahead-of-Time (AOT) or Just-in-Time (JIT) compilation modes: JIT : Compiles in the browser at runtime (used in development). AOT : Compiles at build time into efficient JS (used in production). 🧱 2. View Engine (Legacy Compiler) ➤ Used in Angular versions < 9 🔍 How It Works: Compiles templat...
Read more

Explain the concept of ControlValueAccessor in custom form components.

 In Angular, the ControlValueAccessor interface is what allows custom form components to work seamlessly with Angular forms (both reactive and template-driven). 🧠 What is ControlValueAccessor ? It’s an Angular bridge between your custom component and the Angular Forms API . When you use a custom form component (like a date picker, dropdown, slider, etc.), Angular doesn't automatically know how to read or write its value. That’s where ControlValueAccessor comes in. It tells Angular: How to write a value to the component How to notify Angular when the component’s value changes How to handle disabled state 📦 Common Built-in Examples: <input> and <select> already implement ControlValueAccessor You implement it when creating custom form controls 🔧 Key Methods in the Interface Method Purpose writeValue(obj: any) Called by Angular to set the value in the component registerOnChange(fn: any) Passes a function to call when the component value ch...
Read more

What are the different types of directives in Angular? Give real-world examples.

In Angular, directives are classes that allow you to manipulate the DOM or component behavior . There are three main types of directives: 🧱 1. Component Directives Technically, components are directives with a template. They control a section of the screen (UI) and encapsulate logi c. ✅ Example: @Component ({ selector : 'app-user-card' , template : `<h2>{{ name }}</h2>` }) export class UserCardComponent { name = 'Alice' ; } 📌 Real-World Use: A ProductCardComponent showing product details on an e-commerce site. A ChatMessageComponent displaying individual messages in a chat app. ⚙️ 2. Structural Directives These change the DOM layout by adding or removing elements. ✅ Built-in Examples: *ngIf : Conditionally includes a template. *ngFor : Iterates over a list and renders template for each item. *ngSwitch : Switches views based on a condition. 📌 Real-World Use: < div * ngIf = "user.isLoggedIn...
Read more