I recently found myself wanting the features of the rails asset pipeline in my golang project at work.

Since there isn’t much in the way of asset pipelining for golang yet, I built it.

Turns out, sprockets is really easy to integrate.

Assets in development

First things first - lets get to ‘it works on my machine’.

I’ve put together a sample repo using the asset pipeline.

The setup for your app will be similar:

• The assets folder contains your stylesheets, javascript, etc (this directory name is set in sprockets/environment.rb).
• You’ll need a similar Rakefile to build assets (and maybe launch the server)
• You might store the sprockets directory somewhere else - update the Rakefile to match.
• Use a Gemfile and the bundler rubygem to manage dependencies.
• Edit the rakefile to change the port the asset server runs on.

When your app starts (in development), it should make a request to http://localhost:11111/assets/manifest.json.

Parse this JSON hash; the keys are asset names (eg “application.css”) and the values are relative URLs the compiled assets can be fetched from.

When generating a link to an asset in your app, use the JSON hash you fetched to lookup the URL. In the case of “application.css” this might look like http://localhost:11111/application-8e5bf6909b33895a72899ee43f5a9d53.css.

That should be all you need for development - you should be able to see SASS/Coffeescript assets compiled and loading normally.

Assets in production

For production we want to pre-compile assets rather than regenerating them each time they change.

rake assets will create a ‘public’ folder containing ‘manifest.json’ (same format as before). Get this directory onto your production servers (git add -Af public/ will add it to source control if you deploy via git).

When generating a link to an asset, look up manifest.json (the same as in development, but from the filesystem instead of over HTTP).

Fin

The whole thing, including deployment, took me well under a day to add to our app. The resulting assets are minified, concatenated, and gzipped (for size). They are also fingerprinted (so you can set an unlimited cache lifetime).