To balance clustered nodejs actually generates greater stability

balance.js

const cluster = require('cluster');
const http = require('http');
const httpProxy = require('http-proxy');
const _ = require('underscore');

var numCPUs = 10;
var isPort = 8080;

function estimatePi() {
	var n = 10000000, inside = 0, i, x, y;

	for ( i = 0; i < n; i++ ) {
		x = Math.random();
		y = Math.random();
		if ( Math.sqrt(x * x + y * y) <= 1 )
			inside++;
	}
	return 4 * inside / n;
}

if (cluster.isMaster) {
	var addresses = [];
	var is = 0;
	// Fork workers.
	for (var i = 0; i < numCPUs; i++) cluster.fork();

	httpProxy.createServer(function (req, res, proxy) {
		var add = _.filter( addresses, function (server){
			return _.isNumber( server.port ) && !_.isNaN( server.port );
		});
		is = is >= (add.length * 100) ? add.length - 1 : i++;
		var ReServer = ( is + 1 ) % add.length;
		proxy.proxyRequest(req, res, add[ ReServer ] );
	}).listen( isPort );

	cluster
		.on('online', function (worker){
			addresses.push( { host : 'localhost', port : worker.process.pid } );
		})
		.on('exit', function (worker, code, signal) {
			addresses = _.without(addresses, { host : 'localhost', port : worker.process.pid });
			console.log('worker ' + worker.process.pid + ' died');
			cluster.fork();
	});
} else {
	if(isPort === process.pid )
		return process.exit();
  // Workers can share any TCP connection
  // In this case its a HTTP server
	http.createServer(function (req, res) {
		res.writeHead(200, { 'Content-Type' : 'text/html' });
		res.end('Pi: ' + estimatePi() );
	}).listen( process.pid );
}