How to fork processes in Node.js
Łukasz Holeczek
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Forking creates new Node.js processes that run separate instances of the V8 engine, ideal for CPU-intensive tasks that would block the main event loop. As the creator of CoreUI, a widely used open-source UI library, I’ve implemented process forking in Node.js applications throughout my 11 years of backend development. The most effective approach is using the fork method from the child_process module to spawn Node.js child processes with built-in IPC communication. This method enables message passing between parent and child processes while maintaining process isolation.
Use fork from child_process module to create Node.js child processes with IPC communication.
// parent.js
const { fork } = require('child_process')
const child = fork('./worker.js')
child.on('message', (message) => {
console.log('Received from child:', message)
})
child.send({ task: 'processData', data: [1, 2, 3, 4, 5] })
child.on('exit', (code) => {
console.log(`Child process exited with code ${code}`)
})
Worker file:
// worker.js
process.on('message', (message) => {
console.log('Received from parent:', message)
const result = message.data.reduce((sum, num) => sum + num, 0)
process.send({ result, status: 'completed' })
})
Here fork(’./worker.js’) creates a new Node.js process running the worker script. The parent process uses child.send() to pass messages to the child, while the child uses process.send() to respond. The message event listeners on both sides handle incoming messages. Unlike spawn, fork establishes a communication channel between parent and child processes, enabling structured data exchange. The child process runs independently, preventing CPU-intensive operations from blocking the parent’s event loop.
Best Practice Note:
This is the approach we use in CoreUI build tools for parallel processing of assets and data transformation tasks. Limit the number of forked processes based on available CPU cores, implement proper error handling and process cleanup, and use fork only for Node.js scripts—use spawn for other executables to avoid unnecessary overhead.
