Why are my Rails assets getting precompiled twice? - ruby-on-rails

Question

I've noticed my assets seem to get compiled twice, which considerably slows down my deployment, as this step is the most time consuming part:
~/projects/rewportal(mapwidget ✔) rake assets:precompile
/home/ruy/.rvm/rubies/ruby-1.9.3-p194/bin/ruby /home/ruy/.rvm/gems/ruby-1.9.3-p194#rewportal/bin/rake assets:precompile:all RAILS_ENV=production RAILS_GROUPS=assets
AssetSync: using /home/ruy/projects/rewportal/config/initializers/asset_sync.rb
AssetSync: using /home/ruy/projects/rewportal/config/initializers/asset_sync.rb
AssetSync: Syncing.
Using: Directory Search of /home/ruy/projects/rewportal/public/assets
Uploading: assets/application-5170f52c1dd49cb382d5135bee01d75e.js
[...]
Fetching files to flag for delete
Flagging 8 file(s) for deletion
Deleting: assets/active_admin-4ce46d089d4b0080e87c9abcb6fa6c97.css
[...]
AssetSync: Done.
It this normal?
When I precompile to other environments (non-production), I can see the detailed compilation of each asset twice:
~/projects/rewportal(mapwidget ✔) rake RAILS_ENV=qa assets:precompile --trace
** Invoke assets:precompile (first_time)
** Execute assets:precompile
/home/ruy/.rvm/rubies/ruby-1.9.3-p194/bin/ruby /home/ruy/.rvm/gems/ruby-1.9.3-p194#rewportal/bin/rake assets:precompile:all RAILS_ENV=qa RAILS_GROUPS=assets --trace
** Invoke assets:precompile:all (first_time)
** Execute assets:precompile:all
** Invoke assets:precompile:primary (first_time)
** Invoke assets:environment (first_time)
** Execute assets:environment
AssetSync: using /home/ruy/projects/rewportal/config/initializers/asset_sync.rb
** Invoke tmp:cache:clear (first_time)
** Execute tmp:cache:clear
** Execute assets:precompile:primary
Compiled gmaps4rails/gmaps4rails.base.js (141ms) (pid 8480)
Compiled gmaps4rails/gmaps4rails.googlemaps.js (148ms) (pid 8480)
[...]
Compiled active_admin.css (1299ms) (pid 8480)
Compiled active_admin/print.css (113ms) (pid 8480)
** Invoke assets:precompile:nondigest (first_time)
** Invoke assets:environment (first_time)
** Execute assets:environment
AssetSync: using /home/ruy/projects/rewportal/config/initializers/asset_sync.rb
** Invoke tmp:cache:clear (first_time)
** Execute tmp:cache:clear
** Execute assets:precompile:nondigest
Compiled gmaps4rails/gmaps4rails.base.js (133ms) (pid 8480)
Compiled gmaps4rails/gmaps4rails.googlemaps.js (133ms) (pid 8480)
[...]
Compiled active_admin.css (1290ms) (pid 8480)
Compiled active_admin/print.css (116ms) (pid 8480)
AssetSync: Syncing.
Using: Directory Search of /home/ruy/projects/rewportal/public/assets
Uploading: assets/active_admin-d05b61ab8366b74eabc9074d3e60fe82.css.gz
[...]
Fetching files to flag for delete
Flagging 6 file(s) for deletion
Deleting: assets/active_admin-ec90e7d9a9f45f14d1387f58fa1452b4.css
[...]
AssetSync: Done.
My application.rb has the following:
config.assets.precompile += %w( active_admin/print.css active_admin.css active_admin.js admin.js admin.css html5shiv.js )
Ideas?

Answer 1

Rails 3 by default compiles once to generate fingerprinted assets, and once to generate non-fingerprinted assets (the fingerprinted ones have the MD5 hash in the filename).
You can use the turbo-sprockets-rails3 gem to create both from one compilation.
In Rails 4, this functionality was extracted into the sprockets-rails gem and the behavior was changed, so the double compilation does not happen in Rails 4.

Answer 2

Are you using capistrano? If so, you can try to compile your assets locally, and then upload to server, with a task like this
namespace :deploy do
namespace :assets do
desc "Precompile assets on local machine and upload them to the server."
task :precompile, roles: :web, except: {no_release: true} do
run_locally "bundle exec rake assets:precompile"
find_servers_for_task(current_task).each do |server|
run_locally "rsync -vr --exclude='.DS_Store' public/assets #{user}##{server.host}:#{shared_path}/"
end
end
end
end

Answer 3

I overwrite the deploy_all task inside deploy.rb to compile before uploading:
task :remake_all do
puts "precompiling assets"
res = `env rake assets:precompile:all RAILS_ENV=precompile RAILS_GROUPS=assets 2>&1`
$stderr.puts "assets res is: #{res}"
if res =~ /aborted|don't|invalid|segmentation|bug/i
puts "############ Unable to compile assets #########"
exit
end
end
I had issues with the development environment not compiling properly and the production environment needing access to mysql servers behind a firewall, so made a new environment called :precompile

Answer 4

The solution for me (Rails 3) was to run rake assets:precompile:primary instead of rake assets:precompile:all.