Showing posts from January 20, 2010

ESI: Edge Side Includes

Web page caching gets tricky once personalization is involved. Lets take twitter public_timeline for example which seems to be perfect for caching. Unfortunately when a user is logged in, it also shows the user’s information. Caching that particular page in its entirety, on the web server, in such scenarios, may not be an option. Another scenario is where parts of a page might expire faster than other (require different cache TTLs). Here again caching the whole page doesn’t help. Edge side includes(ESI) is a markup language specifically designed to help web servers assemble dynamic content at the web layer. <esi:include src=""/> The above ESI tag is similar to tags in jsp/php/etc which allow one page to refer to another page for parts of the content on the page. By breaking up the page into smaller objects the webserver could apply different TTL settings (and user validation) to different parts of content. Twitter used to (and may still ) use “ Varnis