understanding cluster plugins

cluster_plugin_1.js

var utils = require('cluster/lib/utils')
	, store = {};

module.exports = function (options) {
	options = options || {};
	ratelimit.enableInWorker = true;
	function ratelimit (master) {
		var server = master.server;
		utils.unshiftListener(server, 'connection', function (sock) {
			sock.pause();
			setTimeout(function(){
				sock.resume();
			}, 25);
		});
	}
	return ratelimit;
};