Merge pull request #4184 from tgxworld/precompile_our_assets_concurrently

PERF: Uglify and gzip assets concurrently.

lib/tasks/assets.rake

@@ -116,6 +116,16 @@ def compress(from,to)
   end
 end
 
+def concurrent?
+  if ENV["CONCURRENT"] == "1"
+    concurrent_compressors = []
+    yield(Proc.new { |&block| concurrent_compressors << Concurrent::Future.execute { block.call } })
+    concurrent_compressors.each(&:wait!)
+  else
+    yield(Proc.new { |&block| block.call })
+  end
+end
+
 task 'assets:precompile' => 'assets:precompile:before' do
   # Run after assets:precompile
   Rake::Task["assets:precompile:css"].invoke
@@ -124,6 +134,7 @@ task 'assets:precompile' => 'assets:precompile:before' do
     puts "Compressing Javascript and Generating Source Maps"
     manifest = Sprockets::Manifest.new(assets_path)
 
+    concurrent? do |proc|
       to_skip = Rails.configuration.assets.skip_minification || []
       manifest.files
               .select{|k,v| k =~ /\.js$/}
@@ -138,6 +149,7 @@ task 'assets:precompile' => 'assets:precompile:before' do
           else
             STDERR.puts "Compressing: #{file}"
 
+            proc.call do
               # We can specify some files to never minify
               unless (ENV["DONT_MINIFY"] == "1") || to_skip.include?(info['logical_path'])
                 FileUtils.mv(path, _path)
@@ -149,6 +161,8 @@ task 'assets:precompile' => 'assets:precompile:before' do
               gzip(path)
             end
           end
+      end
+    end
 
     # protected
     manifest.send :save