ScrobbleAlong

Once again I've moved on to a new project and stopped thinking about my old one, but now that I've wrapped up the new one I guess I really should come back and write something about the old one. This is mainly going to be an "after action report" so that I have an opportunity to go through the technology choices I made and think about what worked and what didn't. I'll go into a bit of technical details but I'm not really 100% happy with the code so I'm not going to put that up anywhere. But first ...

What Is It?

ScrobbleAlong is a website I made which does two (closely related) things. It's a background process that continuously polls the "now playing" feeds of a few radio stations I like and scrobbles all the tracks to last.fm.  It also has a frontend that lets other last.fm users select a radio station that they are listening to so that the songs can also be scrobbled to their account. It's a nifty little tool for people who like to scrobble absolutely everything they listen to, and it's also a nice way to see what various radio stations are playing. If I ever want to see what the latest popular tracks are back home in Australia, I can load up Triple J's last.fm page and check the most played tracks for the last few weeks.

The tool actually has a pretty long history, it started a few years ago as a Python script that just did the radio station scrobbling, but I was looking for something to do as a Node.js project, so I decided to update it and add the "scrobble along" functionality. I'm pretty happy with the way it turned out, if I did it again I would probably do a few things differently, but as a first "proper" Node.js project I think it worked out pretty well.

How Does It Work?

Scrobbling for the stations is handled by a task that runs every 15 seconds, which calls an update function for every station. This update function does a HTTP request for a URL that contains the details for the currently playing song. A parser takes the body of the request and extracts out the artist and song names, and this is compared against the last time the URL was queried. If the song changed since the last request, and it was playing for a long enough time (>30 seconds), the last song is scrobbled. If the new song is valid (e.g. something is actually playing), a "now playing" request is sent to last.fm. One fiddly thing here is that there is no way to tell how long the song will play for, so we tell last.fm that the song is 40 seconds long, and update it again in 30 seconds if it's still playing. 

Scrobbling for users (scrobbling along) is handled mainly using a nice last.fm Node.js module which supports callbacks that are fired when a song has just been scrobbled or a song has started playing. Using this it is fairly easy to have a list of users attached to each station which can be updated whenever the station is updated. Again, some cleverness needs to be applied to avoid problems related to an unknown song length, otherwise only a single now playing notice is sent, so it looks like the user only listens to each song for 30 seconds, then stops listening until the next song starts. For the scrobble along case, this is handled using an interval that fires every 30 seconds and updates the now playing details, which is killed when the song is eventually scrobbled.

The front-end only needs to update the backend storage (MongoDB in my case), which contains a list of users and the station that they are listening to. The stations are presented in a pretty nice way thanks to the Isotope library which works pretty well with Bootstrap to make a nice responsive design. I also chucked a little bit of socket.io in there so that each station "block" automatically updates its display of the latest played tracks.

Lessons Learnt

I used a whole lot of technologies that I'd never used before when writing Scrobble Along, so I'll quickly go through them with some short impressions on what I thought of them.

TypeScript

I've now written a pretty significant project in both TypeScript and plain JavaScript, and I've got to say I really like the safety net and cleaner code that TypeScript provides. I can be a bit annoying sometimes, especially when I was using a definition file that wasn't quite right and I had to keep updating the definition before the app would compile without errors. I also wasted a lot of time writing definitions for modules that didn't have any, which I probably wouldn't bother with again since the time spent was not really worth it. I think in the future I'll continue to use TypeScript but I'll make liberal use of the "any" keyword for modules that don't have any definitions.

Visual Studio

Visual Studio and TypeScript are a great combination. The Intellisense and code navigation options are brilliant. It's a shame that it's not possible to use the debugging tools, but I'm pretty certain I'm going to be using VS for all my TypeScript projects.

Node.js

This was my first attempt at using Node.js and I was very impressed. There are pre-made modules for basically anything you can think of, it reminds me of Python development in that sense. It's also a very rapid development process which is always a good thing. Once I got over my irrational hatred of everything JavaScript and realized that it's not all bad, I really started to enjoy it.

Jade

Using Jade instead of HTML is one thing I'm not sure I'll do again. On one hand, it is more compact and it's nice to be able to do things like looping and conditionals, but on the other hand it's a layer of abstraction around HTML that can be a bit confusing. Maybe my only problem was that Visual Studio doesn't handle Jade files nearly as well as it handles HTML, so I might stick with it but try using Sublime Text to edit it rather than Visual Studio.

MongoDB

I used MongoDB for my data storage, and it's been a great first NoDB experience. It's really easy to use, easy to set up locally, and powerful enough for my needs while still being simple to use. There is also a site called MongoLab that has a generous free tier that I'm using for my production data, so I'm keeping my operational costs at the best price point of $0.

Socket.io

I must admit that I really didn't use Socket.io the best way, mainly due to my inexperience and the fact that by the time I got up to using it I just wanted to get the project finished as soon as I could. Even though I used it really badly, it still worked pretty well for me, and I'm sure I'll find more uses for it now that I almost understand how to use it.

Isotope

This worked out really well for me, but only because I was doing something that was exactly what it was designed for. If I am ever making something that is a grid of things that needs to be able to be rearranged in a responsive way I'm sure I'll use it again.

Bootstrap

I have a love-hate relationship with Bootstrap, it's great when it works but it seems to force pages to be designed in a particular way that doesn't allow much flexibility. I'm sure this is because I'm not a designer and I'm just sticking with the defaults, but I still think I'll try to look into alternatives next time I'm designing a site. I must admit it is really easy to use if you just stick to the defaults though.

The End

So that's another project done! It's a bit buggy, but it works and at least a few other people are using it, so I'm counting it as a success.

Hosted MongoDB connection problems

Just a quick story/solution today so that I don't completely neglect this blog. I recently changed a little project from using Azure to using AppFog, and everything was going fine until I started having some random connection issues with MongoDB. After deployment everything would work fine for a while, but then a few minutes later I wouldn't be able to connect the the database and I just got a random error or timeout.

After scratching my head for a while, Googling around for a solution, and changing my DB layer implementation a few times, I was out of ideas. Then I started to look into my configuration. I have my DB hosted at mongolab and I hadn't updated the hosting location - it was still hosted on Azure, but my AppFog site was hosted on AWS. I didn't think this would be a problem, but I cloned my DB and hosted it on AWS, and then everything started working perfectly.

So if anyone happens to have this problem, and you somehow manage to end up at this site - just make sure that your DB is hosted at the same place as your app.

TypeScript Node.js Development Part 4 - More Packages

In this post I'll go through how to add some useful tools to your Node.js TypeScript app - Underscore for handy utility functions, MongoDB for persistence, and Socket.IO for real-time client-server communication.

Since this is Node, nice people have already made packages for these (underscore, mongodb, socket.io) and adding them is simply done by updating the package.json file:

{
  "name": "package-name"
  , "version": "0.0.1"
  , "private": true
  , "dependencies": {
      "express": "2.5.8"
    , "ejs": ">= 0.8.3"
    , "jade": ">= 0.27.7"
    , "underscore": ">= 1.4.2"
    , "mongodb": ">= 1.1.11"
    , "socket.io": ">= 0.9.11"
  }
}

And since these packages are already included in soywiz's definitions, getting them working in TypeScript is as easy as adding the definitions to the app.d.ts file:

/// <reference path="./node-definitions/node.d.ts" />
/// <reference path="./node-definitions/express.d.ts" />
/// <reference path="./node-definitions/mocha.d.ts" />
/// <reference path="./node-definitions/underscore.d.ts" />
/// <reference path="./node-definitions/mongodb.d.ts" />
/// <reference path="./node-definitions/socket.io.d.ts" />

To test that underscore works, we can add some code to one of our test routes:

import _ = module("underscore")
app.get('/testUrl', function(req, res) {
    console.log('test url ' + req.query['testQS']);

    // Test underscore
    var underscoreTest: string = "";
    var array:string[] = ["a", "b", "c"];
    _.each(array, (item) => { underscoreTest += item });

    res.send(underscoreTest + " env = " + app.settings.env, 200);
});

If you type "_" in to Visual Studio, you'll notice that the TypeScript definitions have given us Intellisense for Underscore, nice!

Socket.IO is also easy to test out, using some of their sample code. We can add this code to our app (again with full Intellisense):

import io = module("socket.io");
var sio = io.listen(app);
sio.sockets.on('connection', function (socket) {
    socket.emit('news', { hello: 'world' });
    socket.on('my other event', function (data) {
        console.log(data);
    });
});

And this code to our index.jade file:

script(src='/socket.io/socket.io.js')
script(type='text/javascript')
  var socket = io.connect();
  socket.on('news', function (data) {
    console.log(data);
    socket.emit('my other event', { my: 'data' });
  });

npm install, then run the app, and we see some console output on the server side logs and the browser, indicating that everything is all going peachy.

MongoDB is a bit more complicated. First, we need to get a local server running so that we can do some testing locally and luckily there is a good tutorial for that over on the MongoDB site. After installation, run mongod.exe and we are ready to write some code to utilize the server.

Here's something I prepared earlier (based on the node package docs), some code that allows addition and querying of a key-value pair to the database (model.ts):

///<reference path='app.d.ts' />

import mongodb = module('mongodb');

interface TestDoc {
    key: string;
    value: string;
}

export class Model {
 private server: mongodb.Server;
 private client: mongodb.Db;

 constructor () {
        var dbname: string = 'testdbsdf';
        var host: string = 'localhost';
        var port: number = 27017;

     this.server = new mongodb.Server(host, port, { auto_reconnect: true });

     this.client = new mongodb.Db(dbname, this.server, { safe: true });
        this.client.open((error) => {
            if(error) { console.error(error); return; }
        });
 }

 putTestDoc(doc: TestDoc, callback: (doc: TestDoc) => void, errorcb: (error: any) => void): void {
     this.client.collection('TestDoc', function (error, docs) {
         if (error) { console.error(error); errorcb(error); return }

         docs.insert(doc, function (error, object) {
             if (error) { console.error(error); errorcb(error); return; }
             callback(object)
         });
     });
 }

 getTestDoc(key: string, callback: (doc: TestDoc) => void, errorcb: (error: any) => void): void {
     this.client.collection('TestDoc', function (error, docs) {
         if (error) { console.error(error); errorcb(error); return; }
            
            docs.findOne({'key': key}, function(error, doc) {
               if(error) { console.error(error); errorcb(error); return; }
               callback(doc);
            });
     });
 }

 getAllTestDocs(callback: (docs: TestDoc[]) => void, errorcb: (error: any) => void): void {
     this.client.collection('TestDoc', function (error, docs) {
         if (error) { console.error(error); errorcb(error); return; }
            
         docs.find({}, { limit: 100 }).toArray(function (err, docs) {
             if (error) { console.error(error); errorcb(error); return; }
             callback(docs);
         });
     });
 }
} 

We can now add some routes that use this class:

import model = module("./model")
app.get('/testMongo/:key/:value', function(req, res) {
    // Add the key/value pair to the DB and then fetch and return it
    database.putTestDoc({ key: req.params.key, value: req.params.value }, function () {
        database.getTestDoc(req.params.key, function (doc) {
            res.send("key = [" + doc.key + "] value = [" + doc.value + "]", 200);
        }, function (err) { res.send(err, 200); });
    }, function (err) { res.send(err, 200); });
});

app.get('/testMongo', function(req, res) {
    // return a list of all pairs
    var response: string = "";
    database.getAllTestDocs(function (docs) {
        _.each(docs, (doc) => { response += ("key = [" + doc.key + "] value = [" + doc.value + "]"); });
        res.send(response, 200);
    }, function (err) { res.send(err, 200); });
});

This is very simplistic - for example, it doesn't check for duplicate keys, but it's good enough to confirm that the database is set up correctly.

So that's all set up locally, but what about ~The Cloud~? Thankfully, The Cloud is generous, and there is a free service to set up cloud-based MongoDB servers called MongoLab. Sign up for an account, create a database, and we are nearly ready to go. Thanks, The Cloud! Before we can use this, we need to modify our model.ts file a bit, so that it can access MongoLab's database. We also now need to authenticate with our username and password. Since we all know that we should never put sensitive information like this in code, we will do this using Azure's app settings. First, we need to update our Model's constructor:

 constructor () {
        var dbname: string = process.env['MONGO_NODE_DRIVER_DBNAME'] || 'testdb';
        var host: string = process.env['MONGO_NODE_DRIVER_HOST'] || 'localhost';
        var port: number = parseInt(process.env['MONGO_NODE_DRIVER_PORT']) || 27017;

     this.server = new mongodb.Server(host, port, { auto_reconnect: true });

     this.client = new mongodb.Db(dbname, this.server, { safe: true });
        this.client.open((error) => {
            if(error) { console.error(error); return; }

            var username: string = process.env['MONGO_NODE_DRIVER_USER'];
            var password: string = process.env['MONGO_NODE_DRIVER_PASSWORD'];
            
            if (username && password) {
                this.client.authenticate(username, password, function (error) {
                    if (error) { console.error(error); return; }
                });
            }
        });
 }

Then we need to put those new settings into our Azure app settings section (in the dashboard, under Configure.

Save those, upload the new code to Azure, and we're up and running all over The Cloud. That's it for now, in the next post, I'll go over testing and debugging your app. As always, here is a Visual Studio template up to this point.

Previously: TypeScript Node.js Development Part 3 - Twitter Bootstrap, next: TypeScript Node.js Development Part 5 - Unit Tests and Debugging