Using the Cluster Module for Scaling

1. Introduction

The Cluster module in Node.js allows you to create child processes that share the same server port. This is an important feature for scaling applications, as it enables better utilization of multi-core systems.

2. Key Concepts

• **Cluster Module**: A built-in Node.js module that provides the ability to create multiple child processes (workers).
• **Worker**: A child process managed by the cluster module.
• **Master Process**: The main Node.js process that manages the worker processes.

3. Getting Started

To use the Cluster module, you need to import it and set up your application. Here's a basic outline:

1. Import the cluster module.
2. Check if the current process is the master.
3. If it's the master, fork worker processes.
4. If it's a worker, run your server logic.

4. Code Example

const cluster = require('cluster');
const http = require('http');
const numCPUs = require('os').cpus().length;

if (cluster.isMaster) {
    // Fork workers.
    for (let i = 0; i < numCPUs; i++) {
        cluster.fork();
    }

    cluster.on('exit', (worker, code, signal) => {
        console.log(`Worker ${worker.process.pid} died`);
    });
} else {
    // Workers can share any TCP connection.
    // In this case, it is an HTTP server.
    http.createServer((req, res) => {
        res.writeHead(200);
        res.end('Hello World\n');
    }).listen(8000);
}
            

5. Best Practices

When using the Cluster module, consider the following best practices:

• Use a process manager (like PM2) to manage your clustered application.
• Handle worker exit events to restart workers if they crash.
• Use load balancing to distribute requests evenly across workers.

6. FAQ