Ignored Cache-Control request header

[Maxim Dounin]

Hello!

On Thu, Mar 13, 2014 at 12:20:41PM -0400, bcx wrote:

> I noticed that the nginx http proxy module by default does nothing with the
> Cache-Control request header that is sent by browsers.
> 
> Most browsers (I tested Crome and Firefox, but from my online research it
> showed that even Internet Explorer has the same behaviour) send a
> Cache-Control: no-cache header when the page requested is with Ctrl-F5 (as
> opposed to a normal F5 or page hit). I would like to configure my nginx
> caching proxy to take this request as an instruction to invalidate the
> cache, send a request to an upstream server, and send and cache that
> response.
> 
> Note that I'm NOT talking about the Cache-Control header sent from upstream
> webservers to the proxy. It's the Cache-Control request headers, not the
> response header.
> 
> Is there a configuration option that I've missed? I spent quite some time
> reading the documentation. Sadly the search terms that I can come up with
> (cache-control, proxy, etc) are too generic for what I want to express.

The proxy_cache_bypass directive can be used for what you are 
looking for, see docs here:

http://nginx.org/r/proxy_cache_bypass

(Note well that in many cases it's not a good idea to allow users 
to bypass server-side cache, as this may be used as a DoS vector.)

-- 
Maxim Dounin
http://nginx.org/