Node Cluster: How to assign a separate server / port to each employee?

Question

I understand that I can use the Nodes cluster module to create several workers serving the same socket connection (example from the docs):

 var cluster = require('cluster'); var http = require('http'); var numCPUs = require('os').cpus().length; if (cluster.isMaster) { // Fork workers. for (var i = 0; i < numCPUs; i++) { cluster.fork(); } cluster.on('exit', function(worker, code, signal) { console.log('worker ' + worker.process.pid + ' died'); }); } else { // Workers can share any TCP connection // In this case its a HTTP server http.createServer(function(req, res) { res.writeHead(200); res.end("hello world\n"); }).listen(8000); } 

However, what if, instead of serving the same connection, I want each worker to run its own server, each of which is listening on a separate port?

Answer 1

You can pass environment variables to each child, allowing the master process to assign ports to them:

 var cluster = require('cluster'); var numCPUs = require('os').cpus().length; if (cluster.isMaster) { var pidToPort = {}; var worker, port; for (var i = 0; i < numCPUs; i++) { port = 8000 + i; worker = cluster.fork({port: port}); pidToPort[worker.process.pid] = port; } console.log(pidToPort); cluster.on('exit', function(worker, code, signal) { // Use `worker.process.pid` and `pidToPort` to spin up a new worker with // the port that now missing. If you do so, don't forget to delete the // old `pidToPort` mapping and add the new one. console.log('worker ' + worker.process.pid + ' died'); }); } else { // Start listening on `process.env.port` - but first, remember that it has // been cast to a string, so you'll need to parse it. console.log(process.env.port); }