Node.js Architecture

Subject: Node.js

Overview of Node.js Architecture

Node.js architecture is based on the Single Threaded Event Loop model, powered by the V8 engine and libuv library.

Major Components:

  • V8 Engine: Compiles JavaScript into machine code
  • libuv: Provides asynchronous I/O and handles the event loop
  • Node.js APIs: Interfaces for file system, HTTP, streams, buffers, etc.
  • Event Loop: Manages asynchronous operations in a single thread
  • Callback Queue: Stores callbacks for execution after async operations complete
  • Thread Pool: Offloads heavy I/O tasks like file system operations and DNS lookups

How Node.js Handles a Request

A simplified flow of how Node.js processes a client request:

  1. Client Request Received: Node.js receives the request on a single thread.
  2. Request is Sent to Event Loop: Lightweight tasks are processed directly.
  3. Heavy I/O is Offloaded: File I/O, database queries, or DNS are sent to the libuv thread pool.
  4. Callback is Registered: Once I/O completes, a callback is pushed into the queue.
  5. Event Loop Executes Callback: The callback is picked up and executed on the main thread.

Diagram: Node.js Architecture (Text-Based)

Code Example: Async Request in Node.js

Output:

Explanation:

  • readFile is non-blocking and offloaded to the thread pool.
  • The rest of the script continues executing.
  • Once the file is read, its callback runs asynchronously.

Key Advantages of Node.js Architecture

  • Scalability: Handles thousands of connections using a single thread.
  • Non-blocking I/O: Continues executing without waiting for operations.
  • Performance: Built with fast V8 and efficient libuv.
  • Low Resource Usage: No need to spawn a thread per request.

When Node.js Architecture is Ideal

  • Real-time applications (chat apps, games, collaboration tools)
  • REST APIs and microservices
  • Streaming services
  • IoT applications
  • Single-page applications (SPAs)

When Not to Use Node.js

  • CPU-heavy tasks like image processing or machine learning

    Because Node.js is single-threaded, intensive computations can block the entire server.

Key Takeaways

  • Node.js uses a single-threaded, event-driven, non-blocking architecture.
  • It integrates the V8 engine for fast JavaScript execution and libuv for async I/O.
  • Multiple requests are handled concurrently without multithreading.
  • Best for building I/O-bound, scalable, and real-time applications.
Next : Node V8 Engine