Clustering in Node.js is used to implement scalable network programs. It is an important technique to ensure smooth application running when a single node process is no longer enough. When a single process is not enough for us to meet the demand, clustering is useful. It will usually increase performance and availability.
To implement clustering in a node.js application, Node.js provides a Cluster module that you can used. Here’s simple example:
```
const cluster = require(‘cluster’);
const http = require(‘http’);
const numCPUs = require(‘os’).cpus().length;
if (cluster.isMaster) { console.log(`Master ${process.pid} is running`);
for (let i = 0; i < numCPUs; i++) { cluster.fork(); } cluster.on(‘exit’, (worker, code, signal) => { console.log(`worker ${worker.process.pid} died`); }); } else { http.createServer((req, res) => { res.writeHead(200); res.end(‘hello world\n’); }).listen(8000); console.log(`Worker ${process.pid} started`); } ```This is the basic usage, how it works is that it starts a master process that will spawn a number of workers (usually as many as our machine has CPU cores). Each worker will run in its own V8 instance, and the master will automatically distribute incoming connections to its workers round-robin.
There are a lot of more complex ways this can be used, but this will let you start an app that can fully utilize your CPU power.
Remember that this doesn’t share any state between workers. If you want to share state, you’ll want to use something like Redis, and if you want to make sure only one worker is doing one thing at a time, you’ll want to use something like RabbitMQ.
