The other day I needed to add an HTML form to the LittleShoot site to upload files directly to Amazon S3. S3’s “browser-based uploads” allow you to send files directly into S3 using hidden form fields to sign the request as opposed to sending files through your server. Nice and efficient.
Everything was going along fine until I realized one glaring problem: how the heck could I set the Content-Type on the file? S3 requires you to do this in the initial request, in this case using another hidden form field, but how could I determine the MIME type at all? Cut past 30 minutes of digging around, and it turns out you can, of course do the following:
- Attach to the form submit event. In JQuery, this is just:
- Dynamically add a hidden “Content-Type” form field just before the upload.
Now comes the beauty of Google App Engine (GAE). With App Engine, you can fire up a site in a matter of minutes that will scale to millions. With a little help from my favorite App Engine Patch, you can run it all on Django. The speed and ease of deployment are breathtaking: 1 hour to deploy a REST API for MIME lookups, all for free.
The result is http://www.mimeapi.org/. It’s a trivial, ridiculously simple API that basically just exposes the Python “mimetypes” module. It’s the simplest, silliest, and most trivial REST API I’ve ever seen or written, and that’s the whole point. Google App Engine annihilates the barrier to creating this type of API on the only two scales that really matter in this case: time and cost.
I predict we’ll see a lot of similarly trivial services continuing to pop up because they’re so easy. They seem almost stupid at first. Simple building blocks like these are the secret sauce in building any truly powerful platform, however, and with tools like GAE, the web is getting more powerful by leaps and bounds.