Try ESI's locally

esi_development.rb

module ApplicationHelper
  
  USE_AJAX_FOR_ESIS = false
  
  def my_render_esi(path)
    response.headers['X-RUN-ESI'] = 'true'
    
    if Rails.env.development?
      
      if USE_AJAX_FOR_ESIS
        div_id = Digest::MD5.hexdigest(path + rand.to_s)
        <<-END

          <div id="#{div_id}"></div>
          <script type="text/javascript">
            var xmlhttp = new XMLHttpRequest();
            xmlhttp.open("GET", "#{path}", false);
            xmlhttp.send();
            document.getElementById("#{div_id}").innerHTML = xmlhttp.responseText;
          </script>
        END
      else
        begin
          require 'net/http'
          url = URI.parse('http://localhost.nytimes.com:3001' + path)
          req = Net::HTTP::Get.new(path)
          res = Net::HTTP.start(url.host, url.port) { |http| http.request(req) }
          res.body
        rescue Errno::ECONNREFUSED => e
          <<-END

            <div style="font-family: sans-serif; font-size: large; background-color: red; color: white; font-weight: bold; padding: 2em;">
              To test ESIs locally, start a second server:
              <pre>rails server -p 3001</pre>
            </div
          END
        end
      end
    else
      '<esi:include src="' + path + '" />'
    end.html_safe
  end
  
end