simple.js

var connectString = "mongodb://user:pass@host:port,host:port,host:port/admin?replicaSet=myset&autoReconnect=true&connectTimeoutMS=1500&socketTimeoutMS=3000";
var mongo = require('mongodb');
var async = require('async');
var admin_db;
var interval = 6000;
var db1;
var db2;
 
var simpleQuery = function(callback) {
	if (db1==null) {
		db1 = admin_db.db('db1');
	}
	db1.collection('foo').save({zoo:1}, {safe:true}, function(err, results) {
		if (err) {
			console.log(err);
		} else {
			db1.collection('foo').findOne({zoo:1}, function (err, results) {
				if (err) {
					console.log(err);
				} else {
					//console.log(results);
					if (db2==null) {
						db2 = admin_db.db('db2');
					}
					db2.collection('bar').save({hi:'there'}, {safe:true}, function (err, results) {
						if (err) {
							console.log(err);
						} else {
							db2.collection('bar').findOne({hi:'there'}, function (err, results) {
								if (err) {
									console.log(err);
								} else {
									//console.log(results);
									setTimeout(callback, interval);
								}
							});
						}
					});
				}
			});
		}
	});
}
 
mongo.connect(connectString, {db: {safe: true}}, function (err, db) {
	if (typeof err !== "undefined" && err !== null) {
		console.log (err);
	} else {
		admin_db = db;
		console.log('connected');
		async.whilst(
			function() {
				return true;
			},
			function(callback) {
				simpleQuery(callback);
			},
			function() {
				console.log("done");
			}
		);
	}
});