How to Make Rails 3 Assets Precompile Faster

How can you speed up the Rails Asset Pipeline precompile process?

1. Capistrano deployment speedup

(1) use capistrano built-in task 'deploy/assets' to deploy.

Capistrano has its own built-in task 'deploy/assets'. It will automatically do task for you.

The difference between your own handcraft task is it only load assets group to precompile assets, not whole environment.

cd /home/apps/APP_NAME/releases/20120708184757 && bundle exec rake RAILS_ENV=production RAILS_GROUPS=assets assets:precompile

(2) skip precompile process when assets aren't changed.

https://gist.github.com/3072362

If

• app/assets
• lib/assets
• vendor/assets
• Gemfile.lock
• confir/routes.rb

are changed, it will recompile assets. Otherwise, it will skip the pecompile process, save a lot of time.

2. Use @import carefully.

(1) avoid using @import "compass"; directly.

It will both work when you

@import "compass"; or @import "compass/typography/links/link-colors"; in SCSS.

But @import "compass/typography/links/link-colors"; is 9 times faster than @import "compass"; when you compile assets.

That is because when @import "compass";, it compile whole compass assets. not only just link-colors part.

(2) avoid using partials

In SCSS, we like to use partial to organize our assets.

But only if you need to share variables, or there are necessary dependencies, otherwise

//= require "reset"
//= require "base"
//= require "product"

is faster than

@import "reset";
@import "base";
@import "product";

3. don’t require .scss & .coffee for no reason

(1) avoid using require_tree

When we use Rails generator to generate controllers. Rails will also generate assets likes this

• product.css.scss
• product.js.coffee

and mount assets in application.js using this techniques:

//= require_tree

But the empty assets (output nothing) which only contain this lines:

# Place all the behaviors and hooks related to the matching controller here.
# All this logic will automatically be available in application.js.
# You can use CoffeeScript in this file: http://jashkenas.github.com/coffee-script/

It will cost you about 250ms to compile each of them. If you have 10 empty assets, it will be 2.5 seconds .

Remove them from your project, or mount them individually in application.js like this:

//= require prodcuts
//= require users
//= require albums

(2) Don't use css.scss or js.coffee if unnecessary.

• Compiled jquery-ui-1.8.16.custom.css (0ms) (pid 19108)
• Compiled jquery.ui.1.8.16.ie.css (0ms) (pid 19108)
• Compiled jquery.js (5ms) (pid 19108)
• Compiled jquery_ujs.js (0ms) (pid 19108)
• Compiled custom.css (14ms) (pid 19108)

custom.css is custom.css.scss

Compile pure CSS and pure JS is fast ( cost almost 0 ms). But compile .scss and .coffee still cost some time.

Summarize

1. replace deploy.rb assets task.

2. check logs/production.log

   • find slow assets
   • remove @import "compass"; use alternative solution.
   • use require instead @import; ( use @import when it is really necessary )
   • remove require_tree, mount assets individually
   • remove empty .scss and .coffeescript
   • use .css when assets are pure CSS.

How do I speed up asset precompiling in Rails 3+?

I am assuming that you are running Rails >3.1.

Don't run the rake tasks at all. Rails development mode doesn't need the assets to be precompiled. Rails will automagically compile the assets when there is a change else it will not.

If you are looking for performance while serving assets in development you can look the gems such as https://github.com/wavii/rails-dev-tweaks

Speed up assets:precompile with Rails 3.1/3.2 Capistrano deployment

The idea is that if you don't change your assets you don't need to recompile them each time:

This is the solution that Ben Curtis propose for a deployment with git:

 namespace :deploy do
      namespace :assets do
        task :precompile, :roles => :web, :except => { :no_release => true } do
          from = source.next_revision(current_revision)
          if releases.length <= 1 || 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

Here is another approach based on asset age (https://gist.github.com/2784462) :

set :max_asset_age, 2 ## Set asset age in minutes to test modified date against.

after "deploy:finalize_update", "deploy:assets:determine_modified_assets", "deploy:assets:conditionally_precompile"

namespace :deploy do
  namespace :assets do

    desc "Figure out modified assets."
    task :determine_modified_assets, :roles => assets_role, :except => { :no_release => true } do
      set :updated_assets, capture("find #{latest_release}/app/assets -type d -name .git -prune -o -mmin -#{max_asset_age} -type f -print", :except => { :no_release => true }).split
    end

    desc "Remove callback for asset precompiling unless assets were updated in most recent git commit."
    task :conditionally_precompile, :roles => assets_role, :except => { :no_release => true } do
      if(updated_assets.empty?)
        callback = callbacks[:after].find{|c| c.source == "deploy:assets:precompile" }
        callbacks[:after].delete(callback)
        logger.info("Skipping asset precompiling, no updated assets.")
      else
        logger.info("#{updated_assets.length} updated assets. Will precompile.")
      end
    end

  end
end

If you prefer to precompile your assets locally you can use this task:

namespace :deploy do
  namespace :assets do
    desc 'Run the precompile task locally and rsync with shared'
    task :precompile, :roles => :web, :except => { :no_release => true } do
      from = source.next_revision(current_revision)
      if releases.length <= 1 || capture("cd #{latest_release} && #{source.local.log(from)} vendor/assets/ app/assets/ | wc -l").to_i > 0
        %x{bundle exec rake assets:precompile}
        %x{rsync --recursive --times --rsh=ssh --compress --human-readable --progress public/assets #{user}@#{host}:#{shared_path}}
        %x{bundle exec rake assets:clean}
      else
        logger.info 'Skipping asset pre-compilation because there were no asset changes'
      end
    end
  end
end 

Another interesting approach can be that of using a git hook.
For example you can add this code to .git/hooks/pre-commit which checks if there are any differences in the assets files and eventually precompiles them and add them to the current commit.

#!/bin/bash

# source rvm and .rvmrc if present
[ -s "$HOME/.rvm/scripts/rvm" ] && . "$HOME/.rvm/scripts/rvm"
[ -s "$PWD/.rvmrc" ] && . "$PWD/.rvmrc"

# precompile assets if any have been updated
if git diff-index --name-only HEAD | egrep '^app/assets' >/dev/null ; then
  echo 'Precompiling assets...'
  rake assets:precompile:all RAILS_ENV=production RAILS_GROUPS=assets
  git add public/assets/*
fi

If you decide to use this approach you would probably need to change your config/environments/development.rb adding:

config.assets.prefix = '/assets_dev'

So that while in development you won't serve the precompiled assets.

rake assets:precompile is slow

If you don't need to load the Rails environment, you should disable that with:

config.assets.initialize_on_precompile = false

EDIT: I've just written a gem to solve this problem, called turbo-sprockets-rails3. It speeds up your assets:precompile by only recompiling changed files, and only compiling once to generate all assets.

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.

rake assets:precompile is slooooow. Any way to speed it up?

You can try to load the assets only on the changed files which would speed up compiling process by a huge margin. You can easily do so using turbo-sprockets-gem.

https://github.com/ndbroadbent/turbo-sprockets-rails3

The documentation is pretty straight forward. Hope this helps.

rake assets:precompile is slow in production

Try to skip compiling ckeditor assets

config/environments/production.rb

  require_relative '../../lib/assets/selective_assets_compressor'
  config.assets.js_compressor = SelectiveAssetsCompressor.new

lib/assets/selective_assets_compressor.rb

class SelectiveAssetsCompressor < Uglifier
  def initialize(options = {})
    super(options)
  end

  def compress(string)
    if string =~ /CKSource/
      string
    else
      super(string)
    end
  end
end

rake assets:precompile taking extremely long to complete

The hackety hack solution seems to be to monkey patch the standard sass compression engine out of the way. I added this to the top of my application.rb

module Sass
  module Rails
    class CssCompressor
      def compress(css)
        css
      end
    end
  end
end

The difference in file size was 124k before the monkey patch and 125k after and an order of magnitude speed improvement.

Rails Assets precompile is too slow ~12hrs

I solved this problem:

The problem was the use of @extend sentence in my .scss files.
This problem appear in this sass version.

I wanted more semantic html files(READ HERE for more information about it).

I found this problem making introspection into Sprockets precompile. With this great tutorial

The solution is take off all @extend sentences from my scss files and use plain bootstrap in my html.

Example: I had to change this.

# main.html
<div class='user-information'> ... </div>

# main.scss
.user-information {
  @extend .col-md-12
}

by this:

# main.html
<div class='col-md-12'> ... </div>

---

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