Thursday, 6 May 2010
RFC5861: HTTP Stale Controls
On a bit of a roll, RFC5861: HTTP Stale Controls has (finally) been published as an Informational RFC.
As discussed before in “Two HTTP Caching Extensions,” these are very useful ways to hide latency and errors from your end users. While they’re most useful in HTTP gateway caches (a.k.a. reverse proxy caches / accelerators), very latency-sensitive sites might find them useful as well when working with “normal” proxy caches.
Both are implemented in Squid 2.7. Not only does Squid respect both response Cache-Control directives, but it also allows you to tweak its behaviour using the stale-while-revalidate and max-stale refresh_pattern options. Squid 3.2 should have them when it’s released, and I understand that Apache Traffic Server will have stale-while-revalidate available soon as well.