expressjsHow do I use Express.js to create a cluster?

Express.js is a web framework for Node.js. It can be used to create a cluster of multiple processes that can run on multiple CPU cores. To create a cluster with Express.js, the cluster module must be used. Here is an example of how to create a cluster with Express.js:

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

if (cluster.isMaster) {
  console.log('Master process is running');

  // 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
  const express = require('express');
  const app = express();

  app.get('/', (req, res) => {
    res.send('Hello from Worker ' + cluster.worker.id);
  });

  app.listen(8000);
  console.log(`Worker ${cluster.worker.id} is running`);
}

This example will create a cluster of numCPUs workers and run an Express.js server on each one. The server will respond to requests with the message Hello from Worker <worker id>.

Code explanation

1. const cluster = require('cluster'); - This imports the cluster module from Node.js.
2. const numCPUs = require('os').cpus().length; - This gets the number of CPUs available on the system.
3. if (cluster.isMaster) {...} else {...} - This checks if the process is the master process. If so, it will fork workers. Otherwise, it will run the Express.js server.
4. cluster.fork() - This is used to fork a worker process.
5. const express = require('express'); - This imports the Express.js module.
6. const app = express(); - This creates an Express.js app.
7. app.get('/', (req, res) => {...}); - This sets up a route that will respond to requests with the message Hello from Worker <worker id>.
8. app.listen(8000); - This starts the Express.js server on port 8000.

For more information on how to use Express.js to create a cluster, please refer to the following links:

• Express.js Clustering
• Node.js Cluster Documentation

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