rake assets:precompile is slow

Question

The command \"rake assets:precompile\" works very slow for me. Especially on my Amazon EC2 Micro production server which does not have a lot of processor resources. On EC2 I

Answer 1

My solution is to exclude application.js .css and any other application related assets from from precompilation. So that i can use rake assets:precompile once to precompile engine related assets only.

Then on each deploy i use a simple rake task to build any application related assets and merge them into manifest.yml:

namespace :assets do
  task :precompile_application_only => :environment do
    require 'sprockets'

    # workaround used also by native assets:precompile:all to load sprockets hooks 
    _ = ActionView::Base

    # ==============================================
    # = Read configuration from Rails / assets.yml =
    # ==============================================

    env           = Rails.application.assets
    target        = File.join(::Rails.public_path, Rails.application.config.assets.prefix)
    assets        = YAML.load_file(Rails.root.join('config', 'assets.yml'))
    manifest_path = Rails.root.join(target, 'manifest.yml')
    digest        = !!Rails.application.config.assets.digest
    manifest      = digest


    # =======================
    # = Old manifest backup =
    # =======================

    manifest_old = File.exists?(manifest_path) ? YAML.load_file(manifest_path) : {}

    # ==================
    # = Compile assets =
    # ==================

    compiler = Sprockets::StaticCompiler.new(env,
                                            target,
                                            assets,
                                            :digest => digest,
                                            :manifest => manifest)
    compiler.compile

    # ===================================
    # = Merge new manifest into old one =
    # ===================================

    manifest_new  = File.exists?(manifest_path) ? YAML.load_file(manifest_path) : {}

    File.open(manifest_path, 'w') do |out|
       YAML.dump(manifest_old.merge(manifest_new), out)
    end

  end
end

To specify which assets to compile i use a YAML configuration file (config/assets.yml):

eg.

---
- site/site.css
- admin/admin.css
- site/site.js
- admin/admin.js