Clusters of Node.js

Node.js's cluster module, which allows for the creation of multiple instances of a Node.js application to utilize multiple CPU cores effectively.

Cluster is following round-robin approach.

Workload is equally distribute in our servers and Handling traffic.

Example of Cluster with Node.js

const express = require('express');

const cluster = require('cluster');

const os = require('os');

const PORT = 3300; // Server port

const numCPUs = os.cpus().length; // Total CPU cores available

if (cluster.isPrimary) {

  console.log(`Master process started with PID: ${process.pid}`);

  // Fork workers for each CPU core

  for (let i = 0; i < numCPUs; i++) {

    cluster.fork();

  }

  // Listen for worker exit and optionally restart

  cluster.on('exit', (worker, code, signal) => {

    console.log(`Worker ${worker.process.pid} exited. Starting a new worker...`);

    cluster.fork(); // Optionally replace the dead worker

  });

} else {

  const app = express();

  // Middleware to log requests

  app.use((req, res, next) => {

    console.log(`Request handled by process ${process.pid}`);

    next();

  });

  // Example routes

  app.get('/', (req, res) => {

    res.send({

      message: `Handled by process ${process.pid}`,

      route: '/',

    });

  });

  app.get('/about', (req, res) => {

    res.send({

      message: `Handled by process ${process.pid}`,

      route: '/about',

    });

  });

  app.get('/contact', (req, res) => {

    res.send({

      message: `Handled by process ${process.pid}`,

      route: '/contact',

    });

  });

  // Start the server

  app.listen(PORT, () => {

    console.log(`Worker ${process.pid} started. Listening on port ${PORT}`);

  });

}