proxy_cache - how to change expires ?

[Cédric Jeanneret]

Hello!

I'm using nginx as a proxy-cache for OSM tiles. My problem is this
sentence in documentation :
"""The cache honors backend's Cache-Control, Expires, and etc since
version 0.7.48"""[1]

I saw that we're supposed to be able to override some headers, like
"expires" with proxy_ignore_headers[2], but it doesn't seem to work.

OSM has an expires set to 3 hours. I'd like to keep tiles for 5 days, so I have:
  proxy_ignore_client_abort on;
  proxy_ignore_headers "Expires" "X-Accel-Expires";
  proxy_cache_valid  200 302  7d;
  proxy_cache_valid  404      1m;

But it seems my cache is really reseted each 3 hours (for now there
isn't many traffic on this vhost, it's just a proof of concept for a
client).

Did I miss something in the documentation ? if so, what ?
Maybe I don't use the right configuration, too. Any hints ?

Thank you !

Best regards,

C.


[1] http://wiki.nginx.org/NginxHttpProxyModule#proxy_cache
[2] http://wiki.nginx.org/NginxHttpProxyModule#proxy_ignore_headers