Force caching for a specific page in Varnish

Just a self-reminder, in the vcl_recv section (before sending request to the backend), check the url you want to always serve from cache and tell it to return(lookup);
  if (req.url ~ "request_server.php$") { return(lookup); }
Reload Varnish and get ready for a massive fall of your load if this bloody request_server.php was overloading your site uselessly...