Flying Machine Studios
adventures in making stuff with Daniel Higginbotham

RubyProfHelper: Reducing ruby-prof Boilerplate

02 June 2008

This is meant to save me from having to write the same boilerplate profiling code over and over.

By default, it creates an HTML graph and saves it to RAILS_ROOT/ruby-prof/profile.html .

The method url_path is a convenience method for saving your HTML graph to a location based on the URL used.

To use, add the below to lib, then add around_filter RubyProfHelper to whatever controllers you want to profile. Then go to the URL you want to profile and add profile=true to the query string. You should probably ensure that this can't be run by any schmoe in production. Also, you'll probably want to have your SCM ignore the ruby-prof directory.

If you want to get more fine grained with your filter, use the following:

RubyProfHelper.run("output_file_name.html") do
  code_to_profile(here)
end

p. When you visit the corresponding URL, leave out profile=true from the query string.

This arguably needs to be a plugin, but I find it more straightforward as a /lib addition.

class RubyProfHelper
  class << self
    def filter(controller, &block)
      return (yield block) unless controller.params[:profile] 

      # Instead of "profile.html" you can try url_path(controller),
      # which will return a file path based on the url visited
      run("profile.html", &block)
    end

    def run(output_file_name = "profile.html", &block)
      require 'ruby-prof'
      RubyProf.start

      yield block

      result                 = RubyProf.stop
      printer                = RubyProf::GraphHtmlPrinter.new(result)

      # create directory
      dir                    = File.join(RAILS_ROOT, "ruby-prof")
      FileUtils.mkdir_p dir

      file_path              = File.join(dir, output_file_name)
      f                      = File.open(file_path, "w+")
      printer.print(f)
    end

    # will evaluate to home.html or something like
    # products.html
    # products/2.html
    def url_path(controller)
      if controller.request.path =~ /\/$|^$/
        "home.html"
      else
        controller.request.path + ".html"
      end
    end
  end
end

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