Saturday, June 8, 2013

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.

3 comments:

  1. Gosh, this is great - especially as Last.fm stopped working for tracks I listened to on Internet radio stations via Clementine. Will check your later blog post on this. I used to listen to KEXP and The End when I lived in Seattle, so I'll be able to scrobble those tracks.

    Do you take requests for other stations? Have a listen to Radio Riel's 6 streams and see what you think. It's a weird little niche, but you might get a kick out of their Steampunk, Dieselpunk, and Reverie channels based on your stations list. www.radioriel.org

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    Replies
    1. No problem - just added all the Radio Riel streams.

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  2. Love this! However, I noticed that ScrobbleAlong seems to be broken with the steam from The Current. I believe they may have just updated their website recently, so maybe that is to blame for it being stuck on the same artist/song in ScrobbleAlong for at least the past day. Is it possible to fix this?

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