Caching issue
Shain Miley
SMiley at npr.org
Sat Mar 8 03:17:35 CET 2008
Thanks alot for the help...I have been trying some of these ideas with little success...even the simple example of 'lookup everything in vcl_recv' did not work...seems to me that should check the cache for everything it receives..which it might have been doing....but it still showed a cache miss..and showed me the 503 error...does anyone know how the matching works...does it only take a hash of the url..or does it use more then that...
Shain
-----Original Message-----
From: varnish-dev-bounces at projects.linpro.no on behalf of Daniel Papasian
Sent: Fri 3/7/2008 5:53 PM
To: Adrian Otto
Cc: varnish-dev at projects.linpro.no
Subject: Re: Caching issue
Adrian Otto wrote:
> I'm not certain if there is a VCL configuration that would cause varnish to
> simply disregard the Pragma and Cache-Control headers from the
> client, because anyone doing a shift+reload while your origin server
> is down is going to get sent back to the origin server as well.
No, I believe it's a simple matter to simply disregard the Pragma and
Cache-Control headers on incoming requests. Most
Most simply, if you wanted to have every request do a lookup from the cache:
sub vcl_recv {
lookup;
}
If the default.vcl I have lying around is still current, then the
default vcl_recv doesn't appear to be looking at Cache-Control or
Pragma, either.
But obviously you probably want to do some checks against
req.http.Cache-Control, req.http.Pragma, req.http.cookie, and perhaps
any other request header, before just blindly doing a lookup in the
cache. There are cases, however, where blindly doing a lookup could
make sense - such as when you are in full control of not only all of the
backends, but also all of the clients (e.g. you are putting varnish in
front of a web application that is used by another one of your systems)
Daniel
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