basic cluster bootloader

cluster.js

var cluster = require('cluster'),
    os = require('os'),
    http = require('http');

// List of 'active' workers:
var workers = [];

var start_count = 0;

// The amount of time we wait before killing a process during a reload:
var DEATH_TIMEOUT = 60000; // 1 minute
var RESTART_TIMEOUT = 50400000; // 14 hours

// Initialize the interval logic
var interval_id;

function startInterval() {
  clearInterval(interval_id);
  interval_id = setInterval(function () {
    console.log("No recent deploys. Restarting...");
    process.kill(process.pid, "SIGUSR2");
  }, RESTART_TIMEOUT);
}

if (cluster.isMaster) {

  os.cpus().forEach(function() {
    workers.push(cluster.fork());
  });

  startInterval();

  process.on('SIGUSR2',function() {
    console.log("Received SIGUSR2 with " + workers.length + " workers running");
    
    console.log("Restart #" + (++start_count));
    startInterval();

    // Blank the worker list, but keep a copy for ourselves:
    var workers_copy = workers.slice();
    workers = [];

    workers_copy.forEach(function (worker) {

      console.log("Disconnecting worker ID " + worker.id);
      worker.disconnect();

      // Timeout, just in case it won't die willingly:
      var savedTimeout = setTimeout(function () {
        console.log("Worker ID " + worker.id + " not responding. Killing process...");
        worker.forced_death = true;
        worker.destroy();
      }, DEATH_TIMEOUT);

      // Worker will raise a disconnect event if it runs through its queue gracefully:
      worker.on('disconnect', function () {

        // Check to see if disconnect is raised because of a force kill:
        if (worker.forced_death) { return; }

        // Else, we just ran through our connections. Cool!
        console.log("Worker ID " + worker.id + " ran through connections gracefully.");
        worker.destroy();
        clearTimeout(savedTimeout);
      });

      // Push this worker's replacement into the new worker list:
      workers.push(cluster.fork());
    });
  });

  cluster.on('exit', function(worker, code, signal) {
    
    // Suicide is if we're the ones who killed it:
    if (worker.suicide) { return; }

    // Else, this shouldn't have died. Restart:
    workers = workers.filter(function(w) { return w.id !== worker.id; });
    if (!worker.reloaded) {
      console.log('Worker ' + worker.id + ' died, forking a replacement');
      workers.push(cluster.fork());
    }
  });

} else {
  var server = require('./app');
  server.listen(3000);
}