A simple cluster module that re-spawns child processes that have died. Also reloads child processes when `require()`d script files have changed.

server.js

var cluster = require('simplecluster').start();

//sorry for not having just cluster.isMaster
if (cluster.cluster.isMaster) {
	//do master stuff if anything at all
	return;
}

//do child process stuff

SimpleCluster.js

/*jslint node: true, maxerr: 50, indent: 4 */

"use strict";

var clusterInstance;

var SimpleCluster = module.exports = function () {
	//there should only be one instance of this per process
	if (clusterInstance) {
		return clusterInstance;
	} else {
		clusterInstance = this;
	}

	var cluster = require('cluster'),
		os = require('os'),
		self = this;

	self.cluster = cluster;
	self.watchedScripts = {};
	self.workers = {};

	/*
	 * forkWorker()
	 * 
	 * Fork a new worker and set up the callback for receiving required scripts
	 * 
	 */
	self.forkWorker = function () {
		var worker = cluster.fork();

		self.workers[worker.pid] = worker;

		worker.on('message', function (msg) {
			if (msg.cmd && msg.cmd === 'registerScripts') {

				(msg.data || []).forEach(function (scriptPath) {
					self.maybeWatchFile(scriptPath);
				});
			}
		});
	};

	/*
	 * maybeWatchFile(path)
	 * 
	 * Conditionally watch a file if we are not already watching it.
	 * 
	 */
	self.maybeWatchFile = function (path) {
		//check to see if we are already watching this script;
		if (!self.watchedScripts.hasOwnProperty(path)) {
			self.watchFile(path);
		}
	};

	/*
	 * watchFile(path)
	 * 
	 * Watch a file and restart workers when it has changed
	 * 
	 */
	self.watchFile = function (path) {
		self.watchedScripts[path] = true;

		require('fs').watchFile(path, function (curr, prev) {
			if (curr.mtime !== prev.mtime) {
				//file has been modified; reload workers

				self.restartWorkers();
			}
		});
	};

	/*
	 * restartWorkers()
	 * 
	 * Restart all workers
	 */
	self.restartWorkers = function () {
		var pid, oldWorkers, worker;

		oldWorkers = self.workers;
		self.workers = {};

		for (pid in oldWorkers) {
			if (oldWorkers.hasOwnProperty(pid)) {
				worker = oldWorkers[pid];

				worker.kill();
				self.forkWorker();
			}
		}
	};

	/*
	 * start()
	 * 
	 * Start the cluster
	 * 
	 */
	self.start = function () {
		if (cluster.isMaster) {
			os.cpus().forEach(function () {
				self.forkWorker();
			});

			process.on('death', function (worker) {
				delete self.workers[worker.pid];

				self.forkWorker();
			});
		} else {
			setInterval(function () {
				process.send({
					cmd : 'registerScripts',
					data : Object.keys(require.cache)
				});
			}, 2000);
		}
	};
};

module.exports.start = function () {
	var c = new SimpleCluster();
	c.start();

	return c;
};