Caching

Different Kind of Caches

• Browser Caches
• Proxy Caches
• Gateway Caches (Reverse Proxy Caches) -> image

HTTP Expiration and Validation

• Expiration = Can i take the ressource from my cache without requesting the server?
• Validation = Check on the server, if my ressource is still valid

Expiration - Expires Header

Expires: Fri, 30 Oct 1998 14:19:41 GMT

• easy to use
• good for static ressources (long caching time)
• Date is based on server time

Expiration - Cache Control Header

Cache-Control: max-age=3600, public

--> image proxy / gateway / browser cache

• max-age=[seconds] - ttl for all caches
• s-maxage=[seconds] - override max-age ttl for proxy caches (proxy/gateway)
• public - MAY be cached by any cache
• private - MUST NOT be cached by a shared cache

Cache-Control is preferred against Expires

Validation - Last-Modified

Response: Last-Modified Request: If-Modified-Since

--

Validation - ETag

Generated by Server Change every time, when representation does

->image

General Tips

• cache as long as possible for dynamic ressources
• static ressources should have a version (change if representation changes)
• split your page in different parts and try to cache every part as long as possible (ESI)

Ressources: http://symfony.com/doc/current/book/http_cache.html http://www.mnot.net/cache_docs/ http://tomayko.com/writings/things-caches-do