I have a server with Ubuntu 14.04.1, Apache at port 8008 and nginx at port 80 as a proxy for Apache. It runs a website based on Wordpress. I use Wordpress's plugin WP Super Cache with the following ...
So we have permalinks in place all over our site. Basically any product, category, article, etc with a "clean url" with canonical such as example.com/green-fidget-widget also have permalink ID ...