The simplest Mongoose app to run

mongoose-test.js

var mongoose = require('mongoose'),
    Schema = mongoose.Schema,
    ObjectId = Schema.ObjectId;

var myS = new Schema({
  name: {type: String, required: true}
});

var My = mongoose.model('My', myS);
var my = new My({'name': 'bika'});
my.save(function(err){
  console.log(err, 'saved');
  db.close();
  process.exit();
});

/** Using only this would never give you a save */
//var db = mongoose.createConnection('mongodb://127.0.0.1:27017/test');

/** You need these */
mongoose.connect('mongodb://127.0.0.1:27017/test');
var db = mongoose.connection
db.on('open', function(err){
  console.log('db open');
  if(err) throw err;
});
db.on('error', function (err) {
  console.log(err);
});

// Just to avoid premature end of script
var express = require("express"),
    app = express.createServer();
app.listen(3000);

For some reason the above code does not save anything to the db, no callback is ever called.