Node.js 0.8.x cluster helper

cluster.js

var cluster = require('cluster');
var config = require('../config.json');
var fs = require('fs');

// Helper module to use cluster.

var pidfile = config.server.pidfile;

// Signals that can be caught and handled.

var signals = [ 'SIGTERM', 'SIGINT', 'SIGHUP' ];

// Initializes and starts cluster.
// Function runOnMaster is run only on the master process
// and function runOnWorker is run only on the worker processes.
// Function runOnWorkerEnd is run on worker shutdown and must
// accept callback.

exports.init = function(runOnMaster, runOnWorker, runOnWorkerEnd) {
    if (cluster.isMaster) {
        master(runOnMaster);
    } else {
        worker(runOnWorker, runOnWorkerEnd);
    }
};

function master(runOnMaster) {
    console.log('Master starting');
    process.title = config.server.masterTitle;
    for (var i = 0; i < config.server.processes; i++) {
        cluster.fork();
    }
    cluster.on('exit', function(worker, code) {
        console.log('Worker exit code ' + code);
        if (!worker.suicide && code !== 0) {
            console.log('Worker ' + worker.process.pid + ' died');
            setTimeout(function() {
                cluster.fork();
            }, 4000);
        }
    });
    signals.forEach(function(e) {
        process.on(e, stopMaster);
    });
    runOnMaster();
    fs.writeFileSync(pidfile, process.pid);
    console.log('Master started');
}

function worker(runOnWorker, runOnWorkerEnd) {
    console.log('Starting worker ' + process.pid);
    process.title = config.server.workerTitle;
    runOnWorker();
    signals.forEach(function(e) {
        process.on(e, function() {
            stopWorker(runOnWorkerEnd);
        });
    });
    console.log('Worker ' + process.pid + ' started');
}

function stopMaster() {
    console.log('Master stopping.');
    Object.keys(cluster.workers).forEach(function(uid) {
        cluster.workers[uid].process.kill();
    });
    fs.unlinkSync(pidfile);
    console.log('Master stopped.');
    process.exit(0);
}

var workerStopping = false;

function stopWorker(runOnWorkerEnd) {
    if (workerStopping) {
        return;
    }
    workerStopping = true;
    console.log('Stopping worker ' + process.pid);
    runOnWorkerEnd(function() {
        console.log('Worker ' + process.pid + ' stopped');
        process.exit(0);
    });
}