Setting headers for negative caching

[Luca De Marinis]

On Wed, Jun 30, 2010 at 5:45 PM, bkirkbri <nginx-forum at nginx.us> wrote:

>> I believe that even if you do, user agents and
>> intermediate caches /
>> proxies may decide not to honour them, so it may
>> be pointless.
>> Regards
>
> That's true in some cases, definitely.  I'd be interested in a list of
> which browsers respect Cache-Control for non-200 repsonses...
>
> But we might throw a reverse proxy cache in front of nginx, which would
> respect those headers and take load off the nginx machine.  Check out
> http://degizmo.com/2010/03/25/why-you-should-upstream-cache-your-404s/

Interesting point, but I believe this is violating standards for
performance (or maybe not, I don't know what the http rfc says about
it), so I'd personally do it only for very good reasons; at our sites
we don't get that many 404s so not caching them for us is preferable.
Anyway if plan on using a reverse proxy it all changes because then
you have fine control on when to purge a certain url, which obviously
you don't have when your headers say "I can be saved by anything in
between for 20 minutes". Even then, when I had to instruct a reverse
proxy, I found it more convenient to use a custom header rather than
munging cache-control, but my scenario was a bit different (I usually
want caching to happen on my proxy, unless some conditions are met,
and never want intermediate caches or UA's to presume they can cache
my dynamic content).

Bye