s-maxage not being honored with proxy_cache
mdounin at mdounin.ru
Wed Apr 24 11:41:59 UTC 2013
On Tue, Apr 23, 2013 at 11:05:58AM -0400, Ryan Parrish wrote:
> I have a slow backend application that I'm using nginx to provide
> the authentication and caching for. It's been working great however there
> is one nagging issue that I cannot seem to resolve, when the backend app
> sets a s-maxage and a maxage Cache-Control, nginx only seems to honor the
> maxage and expires the cache with its value.
> An example response from the backend is like this...
> Cache-Control: max-age=60, s-maxage=3600, public, must-revalidate
> My idea here is I only want the client to cache this data for a short
> amount of time before checking in with me it see if it's still valid. The
> data usually wont be changing that often so I want nginx to cache it for an
> hour, but in the event it does I use the excellent nginx-cache-purge script
> in my backend app to invalidate the cache and the next time a client checks
> in (after 60 seconds) they will get the new data.
Note: you will not be able to purge shared chaches outside of your
control, so this might not work as you expect.
> However in all my testing and usage I will only get a cache HIT for 60
> seconds after the first request to a resource, after 60 seconds it will be
> EXPIRED then it will go to the backend again. Am I missing something in
> the Cache-Control that is causing this behavior?
As of now nginx doesn't handle s-maxage.
Trivial solution is to use X-Accel-Expires to specifi expiration
time for your nginx cache. This should also better match a use
case you've described (as it will only ask your nginx cache to
cache longer, not all shared caches in the world).
More information about the nginx