Just some random node.js load balancing code I wrote about a month ago. It forks child processes for each core on the machine you're on and puts the PIDs into a workers/ directory so you can restart children with commands like "ls workers/* | xargs kill". Not guaranteed to be useful or even work right at this point, just something I spent an eve…

load_balancer.js

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

var app, logger;
var numCores = os.cpus().length;
var workerPidPath = path.join(__dirname, 'workers/');
var masterPidPath = path.join(__dirname, 'master/');

var orderlyShutdown = function(cluster, logger) {
  for(var id in cluster.workers) {
    cluster.workers[id].destroy();
  }

  logger.info("Master " + process.pid + " killed as a result of an orderly shutdown.");
  fs.unlinkSync(masterPidPath + process.pid);
};

module.exports.start = function(app, logger) {
  if (cluster.isMaster) {
    for(var i=0; i<numCores; i++) {
      cluster.fork();
    }

    cluster.on('fork', function(worker) {
      fs.writeFileSync(workerPidPath + worker.process.pid, worker.process.pid);
      logger.info("Worker " + worker.process.pid + " created");
    });

    cluster.on('exit', function(worker, code, signal) {
      fs.unlinkSync(workerPidPath + worker.process.pid);
    
      if (worker.suicide === false) {
        logger.warn("Worker " + worker.process.pid + " killed in a disorderly fashion. Spinning up new worker.");
        cluster.fork();
      } else {
        logger.warn("Worker " + worker.process.pid + " killed as a result of an orderly shutdown.");
      }
    });

    process.on('SIGINT', function() {
     logger.info("SIGINT RECEIVED");
     orderlyShutdown(cluster, logger);
    });

    process.on('SIGTERM', function() {
      logger.info("SIGTERM RECEIVED");
      orderlyShutdown(cluster, logger);
    });

    logger.debug("Master process " + process.pid + " started");
    fs.writeFileSync(masterPidPath + process.pid, process.pid);
  } else {
    http.createServer(app).listen(app.get('port'));
  }
};