How can I make Rails 3 assets precompile faster?

Question

I have a running Rails 3.2.1 application, that I'm deploying via Capistrano with the deploy/assets which runs the deploy:assets:precompile task.

Everything works just fine, except that the compilation itself is really slow. I don't have that much CSS and JavaScript (about 8200 lines total).

It generally takes about 1-3 minutes to compile the assets, which is about 90% of the whole deployment time.

Is there any way to optimize this? Maybe use a different procedure to compile the assets or somehow optimize it?

I'm running the app on Linode 512 on 1.9.2-p290, Rails 3.2.1 and using therubyracer gem if that's of any relevance.

Answer 1

I've just written a gem to solve this problem inside Rails, called turbo-sprockets-rails3. It speeds up your assets:precompile by only recompiling changed files, and only compiling once to generate all assets. It works out of the box for Capistrano, since your assets directory is shared between releases.

It would be awesome if you could help me test out the turbo-sprockets-rails3 gem, and let me know if you have any problems.

Answer 2

This isn't an answer on making it run faster, but as far as a "different procedure" goes, you can tell Capistrano to only precompile assets when you've actually made any changes to your assets. You would want to do a custom assets:precompile task something like this, which would look at the git logs between the existing and newly deployed code. For me, this worked great and now I only need to deal with slow deployment when updating assets:

namespace :deploy do
  namespace :assets do
    task :precompile, :roles => :web, :except => { :no_release => true } do
      from = source.next_revision(current_revision)
      if capture("cd #{latest_release} && #{source.local.log(from)} vendor/assets/ app/assets/ | wc -l").to_i > 0
        run %Q{cd #{latest_release} && #{rake} RAILS_ENV=#{rails_env} #{asset_env} assets:precompile}
      else
        logger.info "Skipping asset pre-compilation because there were no asset changes"
      end
    end
  end
end

Source: http://www.bencurtis.com/2011/12/skipping-asset-compilation-with-capistrano/