nodejsnotes

Topic 010: Clustering in Node.js

Topic 010: Clustering in Node.js

We can implement clustering in Node.js using the built-in cluster module. Clustering allows you to take advantage of multi-core systems by creating multiple instances of your application to handle incoming requests.

Here’s a basic example of how you can implement clustering in Node.js:

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

if (cluster.isMaster) {
  console.log(`Master ${process.pid} is running`);

  // Fork workers equal to the number of CPU cores
  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);

  console.log(`Worker ${process.pid} started`);
}

In this example:

• The cluster.isMaster property is used to determine if the current process is the master process.
• If it’s the master process, it forks worker processes equal to the number of CPU cores available on the system.
• Each worker process handles incoming HTTP requests.
• If a worker process dies (exits), the master process will create a new one to replace it.

To run this code, save it to a file (e.g., cluster.js) and run it using Node.js:

node cluster.js

This will start the master process, which will then fork worker processes. You can test it by opening multiple tabs and sending requests to http://localhost:8000. You should see different worker process IDs handling the requests.