Nodejs App crashed heroku - error failed to connect to localhost:27017

I've been searching for a solution, but anything I've tried gives the same result. I figured it must have something to do with the localhost, but I don't know what's wrong. These are the errors I'm getting when I run heroku logs.

2013-08-05T07:10:34.804131+00:00 heroku[router]: at=error code=H10 desc="App crashed"     method=GET path=/ host=node-beginners.herokuapp.com fwd="59.92.205.141" dyno= connect= service= status=503 bytes=
2013-08-05T07:10:35.424107+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path=/favicon.ico host=node-beginners.herokuapp.com fwd="59.92.205.141" dyno= connect= service= status=503 bytes=
2013-08-05T07:10:35.927263+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path=/favicon.ico host=node-beginners.herokuapp.com fwd="59.92.205.141" dyno= connect= service= status=503 bytes=
2013-08-05T07:20:26.552533+00:00 app[web.1]: Error: failed to connect to [localhost:27017]

My server.js file looks like this.

//create an app server
var express = require('express')
, flash = require('connect-flash')
, helpers = require('view-helpers')
, mongoStore = require('connect-mongo')(express)
, fs = require('fs')    
, mongoose = require('mongoose')
, passport=require('passport')
//create/connect to database
var dbname = 'test';
var uri = 'mongodb://localhost/' + dbname;
mongoose.connect(uri);
console.log('server.js : connecting to %s', uri);
//express settings
var app = express()
app.configure(function() {
app.use(express.static(__dirname + '/public'));
app.use(express.cookieParser('keyboard cat' ));
app.use(express.bodyParser());
app.use(express.methodOverride())
app.use(express.session({
   secret: 'spoc',
  store: new mongoStore({
    url: 'mongodb://localhost/' + dbname,
    collection : 'sessions'
  })
}))
app.use(passport.initialize());
app.use(passport.session());
app.use(flash())
app.use(helpers('node-beginners')) 
app.use(app.router);
});
//start app
var PORT = process.env.PORT || 3000
app.listen(PORT)
console.log('Express app started on port '+PORT)

//expose app
exports = module.exports = app

I've tried almost everything I could find in other posts, but I still get this error. Please help!