Devoxx 2013: HTTP Caching in Practice

Xavier Coulon

types of cache:

• local cache
• proxy cache
• gateway cache
• (app cache -- custom built in the app)

http1.1 caching GET requests

• expiration Last-Modified + Expires headers
• If-Modified-Since header -> 304 not modified
• ETag header
• If-Match & 412 Precondition failed.

prevent inconsistencies: use explicit directives

• Cache-Control
  • request header: no-cache, max-age, no-store, max-stale, min-fresh, no-transform & only ..
  • response: public, private, no-cache, proxy-revalidate, max-age,...
• pragma header, request & response: no-cache: only for http 1.0 backwards compatiblity.
• Refresh button in brower adds Cache-Control and Pragma headers to request. (not in Ajax requests!

java helpers:

• Servlet Filter
• JAX-RS 2.0: interceptors: Ajax-specific (e.g. add ETag + send Status.NOT_MODIFIED)
• testing:
  • Arquillian (+ REST extension)
  • REST-assured

Https:

• proxy caching doesn't work
• decide on using http for static resources...

caching strategy:

• static content:
  • max cache usage
  • enable gateway caching: Cache-Control: public, max-age
• dynamic content:
  • timeout or ETag

RFC 2616 spec (http 1.1): http://www.ietf.org/rfc/rfc2616.txt