Node.JS cluster startup

app.js

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

// Fork child processes.

if (cluster.isMaster) {

    // Run asset cleanup.

    assets.cleanupSync();

    // And when in production mode, compile them
    // into a single file.

    if (process.env.NODE_ENV === 'production') {
        assets.compileSync();
    }

    // Pidfile contains master process PID.
    // This is also used by stop.sh.

    var pidfile = 'master.pid'

    // Map of workers (PID -> worker).

    var workers = {};

    // Set master process title (shows in `ps`).

    process.title = config.server.masterTitle;

    for (var i = 0; i < config.server.processes; i++) {
        var worker = cluster.fork();
        workers[worker.pid] = worker;
    }

    // Emitted on death of a worker.

    cluster.on('death', function(worker) {
        console.log('Worker ' + worker.pid + ' died.');

        // Remove dead worker.

        delete workers[worker.pid];

        // Restart on worker death.

        worker = cluster.fork();
        workers[worker.pid] = worker;
    });

    // Attach signal handler to kill workers
    // when master is terminated.

    function cleanup() {
        console.log('Master stopping.');

        for (var pid in workers) {
            workers[pid].kill();
        }

        // Remove pidfile.

        fs.unlinkSync(pidfile);

        process.exit(0);
    }

    // Master can be terminated by either SIGTERM
    // or SIGINT. The latter is used by CTRL+C on console.

    process.on('SIGTERM', cleanup);
    process.on('SIGINT', cleanup);

    // Write pidfile.

    fs.writeFileSync(pidfile, process.pid);

} else {

    // Set worker process title (shows in `ps`).

    process.title = config.server.workerTitle;

    // Set up the server.

    var server = require('./server').init();

    // Workers are terminated by SIGTERM sent
    // by the master.

    // http://www.oesmith.co.uk/post/15532216845

    process.on('SIGTERM', function () {
        console.log('Stopping worker ' + process.pid);

        // Allow requests finish.

        server.close();
    });

    // When requests are finished, stop the server.

    server.on('close', function () {
        console.log('Worker ' + process.pid + ' stopped');

        process.exit(0);
    });

    console.log('Worker ' + process.pid + ' started.');

}