[PATCH] Upstream: prioritise Cache-Control over Expires

[Maxim Dounin]

Hello!

On Sun, Apr 17, 2022 at 08:50:25PM +0100, Vadim Fedorenko via nginx-devel wrote:

> On 17.04.2022 02:55, Maxim Dounin wrote:
> 
> > I'm quite sceptical about attempts to fix this by introducing
> > various flags and reverting cacheable status back to 1.  This is
> > not how it should be fixed.
> 
> Yeah, the solution might be a bit complicated, but I couldn't find
> another way without breaking concept of independent header parsing.
> Could you please suggest something if you think that current approach
> is wrong? The ticket that this patch tries to fix is 6 years old and
> still has discussions going on without any solution.

That's basically why the ticket is still not fixed: there is no 
easy fix, and the issue is rather minor, especially compared to 
the complexity of the changes required to fix it.

IMHO, the most promising approach would be to move 
Cache-Control/Exires/X-Accel-Expires handling elsewhere, and 
handle them somewhere in ngx_http_upstream_process_headers(), 
probably along with ngx_http_file_cache_valid() as well.

-- 
Maxim Dounin
http://mdounin.ru/