gistfile1.js

// estamos usando mongoskin (npm install mongoskin)
var mongoskin = require('mongoskin');

// Si te estas conectando a un cluster con replica set, etc.
var matches = /mongodb:\/\/([^:]+):([^@]+)@([^\/]+)\/(.*)/.exec(process.env.MONGOLAB_URI);
var servers = matches[3].split(',').map(function(e){ return e + "?auto_reconnect=true&poolSize=4"; });
var dbOpts = {username: matches[1], password: matches[2], database: matches[4], safe: true, native_parser: false };
var socketOptions =  { keepAlive: 1, connectTimeoutMS: 0, socketTimeoutMS: 0};

var db = mongoskin.db(servers, dbOpts, { rs_name: "rs-ds041197", socketOptions: socketOptions });

// Si te estas conectando derecho a la base
var db = mongoskin.db(process.env.MONGOLAB_URI + "?auto_reconnect=true&poolSize=4", {safe: true});

module.exports = db;