gistfile1.js

var cluster = require('cluster'),
    redis = require("socket.io/node_modules/redis"),
    numCPUs = require('os').cpus().length;

if (cluster.isMaster) {

    //master process - fork children
    for (var i = 0; i < numCPUs; i++) {
        cluster.fork();      
    }

    // child handlers
    cluster.on('exit', function(worker, code, signal) {
      console.log('worker ' + worker.process.pid + ' died');
    });
    cluster.on('disconnect', function(worker, code, signal) {
      console.log('worker ' + worker.process.pid + ' disconnected');  // exit soon to follow
    });
    cluster.on('online', function(worker) {
      console.log('worker ' + worker.process.pid + ' is online.');
    });


    // configure socket server
    var RedisStore = require('socket.io/lib/stores/redis')
        , pub    = redis.createClient()
        , sub    = redis.createClient()
        , client = redis.createClient();

    //start socket.io
    var io = require('socket.io').listen(5000, {
        'store' :new RedisStore({
                redisPub : pub
              , redisSub : sub
              , redisClient : client
        }),
    });

    // socket event routing

    io.sockets.on('connection', function (socket) {

      console.log('Socket connected on master. Socket='+socket);

      socket.on('disconnect', function () {
        console.log('Socket disconnected');
      });
      socket.on('event', function (data) {
        console.log('Socket event on master. Data='+JSON.stringify(data));
      });
      socket.on('hello', function (data) {
        console.log('Socket HELLO event on master. Data='+JSON.stringify(data));

        var randomIndex = Math.floor(Math.random()*numCPUs)+1;
        var someWorker = cluster.workers[randomIndex];
        if ( someWorker === undefined ){
          console.log('Random index ='+randomIndex);
          return;
        }
        someWorker.send(data);
      });
    });

    io.sockets.on('disconnect', function () {
          console.log('Something disconnected on master');  // wtf is this? Not when a socket closes
    });
    io.sockets.on('error', function () {
          console.log('Socket error on master');
    });

} else {

    var worker = cluster.worker;
    var pid = worker.process.pid;
    console.log('Worker '+pid+' is alive!. Worker ID is '+worker.id);

    worker.on('message', function(data) {
      console.log('message received on '+pid+'. Data= '+JSON.stringify(data));
    });

}