The Web Service

This page of the Playlister case study describes the "cloud" web service that provides playlist data to the iPhone application.

I built the web service on the symfony PHP framework and deployed it on one of Dreamhost's private server instances.

The web service infrastructure for the Playlister application is what makes the ten-fold improvement in load times possible. It applies two simple approaches:

1. Resource-intensive tasks are off-loaded to the fast server where the web service runs, e.g. determining whether a song is available on the iTunes Music Store, finding album cover art, etc.
2. Only the minimum info needed to tell me what song is playing is sent to the iPhone.

Regarding the first point, here is a diagram that depicts the flow of Playlister data on its way to the iPhone. The Playlister iPhone application would be very slow if it had to make separate requests to KEXP and Apple and then process that data. So the Playlister Web Service takes care of all that, allowing the iPhone application to get all the data it needs in a single, concise, request.

And the next image below is a graphic comparison of the amount of data sent from the Playlister web service versus the full playlist page to illustrate the second point from above. The page load time difference between these examples are small on a desktop or laptop computer, but it makes a huge difference for mobile applications where your audience may be using EDGE for network access. Even when your users have WiFi access, it taxes the limited resources of the iPhone to render complicated markup and Javascript, and that shows in slow page load times.

So I have a web service that is ready to provide quick-to-load nuggets of song data. Time to look at the iPhone application itself.