Cannot execute Node.js app on Heroku successfully (crashes each time)

Question

I have attempted to put together a sample node.js app on Heroku basically as per their instructions here: https://devcenter.heroku.com/articles/nodejs

The app runs fine locally with foreman start, however, each time I deploy the app it crashes. What am I doing wrong?

My Procfile contains:

web: node web.js

My package.json contains:

{
  "name": "testapp",
  "version": "0.0.1",
  "engines": {
      "node": "0.6.15"
    , "npm": "1.1.9"    
  }
  , "dependencies": {
    "tower": "0.4.0-12"
  }
}

My web.js contains:

var express = require('express');

var app = express.createServer(express.logger());

app.get('/', function(request, response) {
  response.send('Hello World!');
});

var port = process.env.PORT || 3000;
app.listen(port, function() {
  console.log("Listening on " + port);
});

The app deploys and starts up, yet crashes each time. The log output I see from the app is:

2012-04-27T20:21:31+00:00 heroku[web.1]: State changed from created to starting
2012-04-27T20:21:37+00:00 heroku[web.1]: Starting process with command `node web.js`
2012-04-27T20:21:38+00:00 app[web.1]: 
2012-04-27T20:21:38+00:00 app[web.1]: node.js:201
2012-04-27T20:21:38+00:00 app[web.1]:         throw e; // process.nextTick error, or 'error' event on first tick
2012-04-27T20:21:38+00:00 app[web.1]:               ^
2012-04-27T20:21:38+00:00 app[web.1]: Error: Cannot find module 'express'
2012-04-27T20:21:38+00:00 app[web.1]:     at Function._resolveFilename (module.js:332:11)
2012-04-27T20:21:38+00:00 app[web.1]:     at Function._load (module.js:279:25)
2012-04-27T20:21:38+00:00 app[web.1]:     at Module.require (module.js:354:17)
2012-04-27T20:21:38+00:00 app[web.1]:     at require (module.js:370:17)
2012-04-27T20:21:38+00:00 app[web.1]:     at Object.<anonymous> (/app/web.js:1:77)
2012-04-27T20:21:38+00:00 app[web.1]:     at Module._compile (module.js:441:26)
2012-04-27T20:21:38+00:00 app[web.1]:     at Object..js (module.js:459:10)
2012-04-27T20:21:38+00:00 app[web.1]:     at Module.load (module.js:348:31)
2012-04-27T20:21:38+00:00 app[web.1]:     at Function._load (module.js:308:12)
2012-04-27T20:21:38+00:00 app[web.1]:     at Array.0 (module.js:479:10)
2012-04-27T20:21:39+00:00 heroku[web.1]: Process exited with status 1
2012-04-27T20:21:40+00:00 heroku[web.1]: State changed from starting to crashed
2012-04-27T20:30:01+00:00 heroku[router]: Error H10 (App crashed) -> GET testapp.herokuapp.com/ dyno= queue= wait= service= status=503 bytes=

Answer 1

It appears you are requiring express in your web.js, so why you do not add express to your dependencies? Your local copy may have express installed already, that's why you are not getting any error. Tower may require express, however, you cannot directly access express from it, it is a submodule in tower's directories, not in your app directory.