Generate Gzipped Assets in Rails 4.2 +

Doesn’t Rails generate gzipped assets on running rake assets:precompile? It did so, until Rails 4.2. What changed?

Rails uses sprockets gem, for compiling and serving web assets. Before Sprockets 3 was introduced, rake assets:precompile generated .gz versions for all the assets.

This change, seems backward, for several reasons

1. Gzipping should always be enabled for static assets. It’s super charges serving of static content.
2. Assets should be gzip’ed beforehand as part of the build process, rather than letting the webserver do it on the fly, saving on CPU cycles.
3. Also, Nginx has the ability to serve static .gz files directly, by using the gzip_static on; directive.

The reason for dropping this, was its incompatibility with Apache.

Since Sprockets 3 dropped this feature, it means Rails had to loose it too. The Rails team, plans to bring it back as an opt-in. Nevertheless, what does one do in the meantime?

Here are the options to generate Gzipped Assets with Rails

1. depends on parallel gem to use multiple CPU cores, but can easily be simplified
2. gzip assets with Capistrano
3. write an assets:gzip rake task that plugs into assets:precompile (mentioned below)

namespace :assets do
  desc "Create .gz versions of assets"
  task :gzip => :environment do
    zip_types = /\.(?:css|html|js|otf|svg|txt|xml)$/

    public_assets = File.join(
      Rails.root,
      "public",
      Rails.application.config.assets.prefix)

    Dir["#{public_assets}/**/*"].each do |f|
      next unless f =~ zip_types

      mtime = File.mtime(f)
      gz_file = "#{f}.gz"
      next if File.exist?(gz_file) && File.mtime(gz_file) >= mtime

      File.open(gz_file, "wb") do |dest|
        gz = Zlib::GzipWriter.new(dest, Zlib::BEST_COMPRESSION)
        gz.mtime = mtime.to_i
        IO.copy_stream(open(f), gz)
        gz.close
      end

      File.utime(mtime, mtime, gz_file)
    end
  end

  # Hook into existing assets:precompile task
  Rake::Task["assets:precompile"].enhance do
    Rake::Task["assets:gzip"].invoke
  end
end

Reading Code

Writing documentation, is harder than writing code.

If you thought writing code is harder, my experience tells me that writing documentation even more so!

In the calculus of communication, writing coherent paragraphs that your fellow human beings can comprehend and understand is far more difficult than tapping out a few lines of software code that the interpreter or compiler won’t barf on. ~ Coding Horror

If its not documented, it doesn’t exist.

For open source projects, ‘getting started’ documentation is usually good these days. But once you run into some obscure issue or an edge case – you would have to resort to reading the code and documentation would mostly fail.

This is the time, when people are encouraged to document there finding and help out improving documentation. But as it would, code moves at a far more pace than documentation can.

Reading Code

Reading code might be an incidental task that you do while figuring out the issue with the code. But, it should actually be done as an activity of its own too. It’s widely agreed that reading great code definitely improves one’s own programming skill.

My experience while doing these ‘code reading’ exercises have been a revelation in terms of the knowledge that one can gather and the depth of the understanding.

I have realized that reading through the issues and comments listed on rails, has made me more knowledgeable with the code base than the documentation itself could ever do. Also, reading through such a huge code base like rails – is difficult to understand just by reading it. The issues and the comments / discussion on them is the best form of documentation. More like FAQs.

Smitten by this habit of reading through issues and the comments – I have decided to start *documenting* these understandings as blogpost series where I would take up the issue listed on rails/rails and then document my understanding of the behavior and summarize the comments.

Hopefully, that’s going to be helpful to all of us

– Code Reading Groups – Code is not Literature