Setting headers for negative caching

Server NGINX
1

Is it possible to set Cache-Control / Expires headers for 404 responses
in Nginx?

I’ve tried using an error_page like this:

location ^~ /x/ {
    error_page  404  /not_found.html;
}
location /not_found.html {
    internal;

    root /static/errordoc;
    expires 10m;
    add_header Cache-Control "private, max-age=600";
}

But no luck.

Thanks in advance!

Posted at Nginx Forum:

2

On Mon, Jun 28, 2010 at 6:54 PM, bkirkbri [email protected] wrote:

Is it possible to set Cache-Control / Expires headers for 404 responses
in Nginx?

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

3

Luca De Marinis Wrote:

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/

Best,
Brian

Posted at Nginx Forum:

4

On Wed, Jun 30, 2010 at 5:45 PM, bkirkbri [email protected] wrote:

respect those headers and take load off the nginx machine. Â 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

5

Luca De Marinis Wrote:

interested in a list of

you have fine control on when to purge a certain
conditions are met,
and never want intermediate caches or UA’s to
presume they can cache
my dynamic content).

Bye

All good advice, thanks.

For what it’s worth, the HTTP spec does allow caching of 404, 302, 301,
etc. responses if the Cache-Control header is set explicitly by the
origin. The spec forbids any caching of these responses without a
Cache-Control header though, which is in contrast to the allowed
behavior of caching 200 responses that do not have Cache-Control headers
for some reasonable amount of time.

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