Difference between spawn() and fork() methods in Node.js

Last Updated : 12 Jun, 2024

Node.js provides several ways to create child processes, enabling you to run tasks in parallel and leverage multi-core systems efficiently. Two commonly used methods for this purpose are spawn() and fork(). While they might seem similar, they serve different purposes and have distinct features. This article will explore the differences between spawn() and fork() in Node.js.

Table of Content

Overview of Child Processes in Node.js
The spawn() Method
The fork() Method
Difference between spawn() and fork()
Conclusion

Overview of Child Processes in Node.js

Child processes in Node.js allow you to execute other applications or scripts within your Node.js application. This is particularly useful for performing CPU-intensive operations, managing subprocesses, or executing commands.

The `child_process` Module

Both spawn() and fork() are part of the child_process module in Node.js, which provides various methods to create and control child processes. To use these methods, you first need to require the module:

const { spawn, fork } = require('child_process');

The `spawn()` Method

The spawn() method is used to launch a new process with a given command. It allows you to execute external commands and interact with the child process’s input and output streams in real time.

const child = spawn(command, [args], [options]);

command: The command to run.
args: An array of string arguments.
options: An object specifying additional options.

Return Value:

It returns an instance of the child process.

Features

Real-time Streaming: spawn() streams data between the parent and child process in real time, making it suitable for long-running processes.
Raw I/O: It provides access to raw input and output streams (stdin, stdout, stderr).
Independent Process: The child process runs independently of the parent process.

Example: This is a very simple and general example of the use of spawn. We first required spawn by destructuring, then create a child process by passing arguments. Then register a stdout event on that child process.

JavaScript

const { spawn } = require('child_process');
const child = spawn('dir', ['D:\\empty'], { shell: true });

child.stdout.on('data', (data) => {
    console.log(`stdout ${data}`);
});

Output:

Message sent from child.js is printing in file server.js due to the use of fork child process.

The `fork()` Method

The fork() method is a specialized version of spawn() that is specifically designed for spawning new Node.js processes. It creates a new instance of the V8 engine to run a separate Node.js script.

const child = fork(modulePath, [args], [options]);

modulePath: The path to the Node.js module to run in the child process.
args: An array of string arguments.
options: An object specifying additional options.

Features:

IPC (Inter-Process Communication): fork() establishes a communication channel (IPC) between the parent and child process, allowing for message passing.
Optimized for Node.js: It is optimized for spawning new Node.js processes, inheriting the environment and execution context.
Separate V8 Instance: Each forked process has its own V8 instance, making it more isolated.

Example: Implementation to show the use of fork method.

JavaScript

// index.js

const { fork } = require('child_process');

const child = fork('child.js');

child.on('message', (message) => {
  console.log('Message from child', message);
});

child.send({ hello: 'world' });

JavaScript

// child.js

process.on('message', (message) => {
  console.log('Message from parent:', message);
  process.send({ response: 'Hello from child' });
});

Output: