If you’re deploying a high traffic site, I can see this perhaps being a slight issue. However, in that case, you’d probably have a staging server for CruiseControl and Selenium/screw_unit (or equivalent) which would mitigate the particular risk of live files not being tested before they were put into production.

I agree that if you don’t have a staging environment, performing concatenation before minify could be a tad risky. In that particular case, doing minify first would be more desirable.

The risk comes from running yuicompressor on live files. Capistrano is designed to prepare the entire directory first, then switchover in a flash by changing the symlink. What you’re advocating in this post goes outside that philosophy by modifying the files in the currently running application.

yuicompressor -> Rails concatenate

Versus the more complicated flow described in this blog post:

Rails concatenate -> yuicompressor

There is a lot of extra work here to reverse the natural order of these two steps and get Rails to concatenate first. Waiting for the server to restart, wget, etc. It’s messy. And — perhaps more importantly — the compression step really should be done before deploy:symlink. Otherwise you risk the server sending uncompressed js to an end user, or even worse: if the server happens to read the file at the same time as yuicompressor is writing it, it could send a partial js file.

My point is the difference in the size of the final *.js file is insignificant. Literally just a few bytes, including all of Prototype and Scriptaculous.

I tried to diff them but since each file is one huge line, it was not really possible to see the difference, but I suspect the only difference is that the more complicated flow eliminates the newlines between the concatenated files. Hardly worth the added complexity and risk.

Here’s my recipe to compress each js and css file. [I hope the formatting works...]

after “deploy:update_code”, “deploy:minify”

namespace :deploy do
task :minify, :roles => :web do

def go(ext, path)
compressor = “java -jar /opt/yuicompressor-2.4.2/build/yuicompressor-2.4.2.jar”
path = File.join(release_path, “public”, path)
run “for i in #{path}/*.#{ext}; do #{compressor} –type #{ext} -o $i $i; done”
end

go ‘js’, ‘javascripts’
go ‘css’, ’stylesheets’
end
end

As for letting Rails perform the concatenation, isn’t that what < %= javascript_include_tag 'jquery', 'ninja', :cache => ‘all’ %> does?

The wget business is due to weird issues with our load balancer. This was necessary to force Rails running on Phusion Passenger to perform the concatenation on all of our production servers.