mongo.js

var MongoClient = require('mongodb').MongoClient;

var OPTIONS = { db: { native_parser: false }, replSet: { keepAlive: 1, connectTimeoutMS: 0, socketTimeoutMS: 0 } };

var current = null;

module.exports = function(callback) {
  if(current && (current._state == 'connected' || current.serverConfig.isConnected())) {
		return callback(current);
	}

	var url = process.env.MONGOLAB_URI + "?auto_reconnect=true&poolSize=4";
	MongoClient.connect(url, OPTIONS, function(err, db) {
		if(err) throw err;

		return callback(current = db);
	});
};