To ignore clients headers regarding cache this should be enough imo:
sub vcl_recv {
unset req.http.Cache-Control;
}
You can also override the backends cache settings.
For example because of some performance concerns (in case of broken image/resource the backend wont be hammered by the client
againt) we do something like this (in case the backend server "decides" to return something with less than 10 minutes cache
timeout):
sub vcl_fetch {
if (beresp.ttl < 10m) {
set beresp.ttl = 10m;
}
return (deliver);
}
rr
----- Original Message -----
From: <[email protected]>
To: <[email protected]>
Sent: Friday, May 28, 2010 4:15 PM
Subject: Ignoring refresh / force-refresh from the client
Hi guys,
I'm working with a client who has an emergency (a backend webapp misbehaving because of sluggishness under load), so I deployed
varnish in front to relieve the load.
The input from the customer is that the underlaying data doesn't change more often that 4 hours, so it would be good to be able
to not send requests for a given URL more often than that.
The basic setup was a piece of cake, but I'd like to also "lie" to users that hit refresh (and even forced refresh, if possible)
and still serve the request from the cache, as long as the page is fresh.
However in my tests a refresh from e.g. Firefox (with a "Cache-Control: max-age=0") causes the URL to be purged from the cache
and fetched from the backend.
AFAICT obj.cacheable is still true, so I'm not sure why is that happening.
I've tried unsetting/removing req.http.cache-control and had no success.
I've also tried sending Age: 0, also no success.
Any suggestion, or pointer to documentation/blog posts/source code/whatever?
In case it matters: the backend is sending an Expires header 4 hours in the
future, no ETag. I'm also sending a max-age.
Thanks in advance, bye,
Andrea
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