Tag: Ruby

Rails 3.1 – Sending Content-Length header using middleware – Rack::ContentLength

September 4, 2011 /

Some of applications need to send content-length header in every request. For example, when sending something to a mobile device - it would be nice to tell this device how much data are we sending, so the mobile user could see real progress bar.

How to do it in Ruby on Rails 3.1? Well, here you have a list of rack middleware. There is one called Rack::ContentLength, which we will be using. To do so, just include following line into application.rb:

    config.middleware.use Rack::ContentLength

There is a lot interesting stuff going on in rack middleware. For example you can also see this Railscast for more details.

Here example of full response header containing content-length:

Date	Sun, 04 Sep 2011 12:46:46 GMT
Server	Apache/2.2.14 (Debian)
X-Powered-By	Phusion Passenger (mod_rails/mod_rack) 2.2.11
Etag	"a464ed7f54b5637d393232d9dbd40523"
X-UA-Compatible	IE=Edge,chrome=1
X-Rack-Cache	miss
X-Runtime	0.039739
Cache-Control	must-revalidate, private, max-age=0
Content-Length	888
Status	200
Keep-Alive	timeout=15, max=100
Connection	Keep-Alive
Content-Type	application/json; charset=utf-8

Rails 3.1 RC5 + CSS and JS compression + undefined method `compress’ for :scss:Symbol in production mode

August 14, 2011 /

When running Rails 3.1RC5 with environments/production.rb containing:

  config.assets.js_compressor  = :uglifier
  config.assets.css_compressor = :scss
  config.assets.compress = true

probably you will see this type of exception:

undefined method `compress' for :scss:Symbol
  (in /home/path/app/assets/stylesheets/layouts/admin/default/init.scss)

But why? Lets go deeper ;) JS and CSS compression is quite simple. We have uncompressed stuff - we throw it into compressor and we have compressed version on output. Rails compression engine executes method called compress with one string parameter containing uncompressed stuff. We should also return string - containing input string compressed version.

Since we point out symbol as our default compressor - Rails will try to execute compress on this symbol. How can we fix this? There are two ways. First one is easy - screw compression:

  config.assets.compress = false

Second one is slightly more difficult (but still easy). We just need to attach our own compressors.

Javascript compression

Lets use Uglifier to compress our JS. We need to add it into gemfile

gem 'uglifier'

and we need to tell Rails - that it should use it to compress JS(in environments/production.rb):

  # Put this on top of production.rb file
  require 'uglifier'
  # Somewhere in the "middle"
  config.assets.js_compressor  = Uglifier.new

CSS compression

I compress CSS using my own compressor. It is a hybrid compressor including SASS and my own CSS Image Embeddera. I've managed to have SASS one line compression and embedded css backgrounds. How to use it?

Add into gemfile:

gem 'css_image_embedder'

and then attach my compressor in environments/production.rb:

  img_root = File.join(Rails.root, 'public')
  config.assets.css_compressor = CssImageEmbedder::Compressor.new(img_root)

Conclusions

CSS and JS compression worked really well already in Rails 3.0. However now we can easily get into whole process and do cool stuff (like css image embedding ;) ).

[Update] One more thing: from now I will be posting only in english.

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