code: function fork(number) {
    var numProc = number || require('os').cpus().length;
  
    config.n = numProc;
  
    debug('forking %d workers', numProc);
  
    forkLoopProtect();
  
    for (var i = 0; i < numProc; i++) {
      cluster.fork({PWD: config.CWD});
    }
  }
docs: Fork Workers N times
  
  @private
  @param {int} [number=cpus.length] the number of processes to start