Weekend appengine project: symlinkd.com

posted in programming by jon on 2009-11-06

A few weekends ago I got an itch to play around with Appengine, and was trying to think of something suitably simple.

One idea that had been banging around in my head for awhile was a simpler take on dynamic DNS (ala dyndns). I've had a dyndns account forever, but it annoyed me that they periodically deactivated my account until I logged in and 're-confirmed' that it was active.

This was especially irritating to me because they problem they're solving (storing an IP address and updating the value) isn't really a difficult one. Essentially, since I could easily obtain the originating address from an incoming HTTP request, all I really needed was to request a unique address, record the originating host, and have a way to retrieve that information on demand.

Further, it occurred to me that URL shorteners (like tinyURL) have some overlap here: they also have a unique address (or 'handle') that refers to some recorded value and a method for redirecting you there. So, I decided to make a single app that does both: a 'tinyURL' that's easy to programmatically update with the originating IP of the computer making the update request.

Moreover, I decided that since each 'handle' might change frequently, it might be nice to provide a persistent history of when and how it changed. After implementing this, I realized that, as a cool side effect, it makes it possible to use a link handle like a categorized bookmark list. Naturally, then, I'd need to make each handle subscribable to better suit this use case.

Thus, with a few hundred lines of python/html and a dab of javascript, symlinkd was created. It was mostly built in one evening in front of the TV, though I fiddled with it for a few evenings afterward. It mostly does what I want it to do, though I'll likely continue to poke at it.

Overall, I'm happy that I can now use curl to update my home IP address (rather than dyndns's binary blob client), and that I have my own personal URL shortener ;)

Random thoughts and things I learned:

  • I don't think I like datastore, and I'm quite sure I don't really like GQL
  • the minimalistic 'webapp' framework created for appengine is pretty serviceable
  • getting user auth for free is a nice side effect of using appengine
  • adding pubsubhubbub support to a content feed is really, really easy
  • I like the Atom protocol for publishing syndicated content, especially when I'm generating the feed template manually.
  • you can't use subdomains with appengine if you want to use your own domain (instead of .appspot.com)

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