Re: no_cache tag..

From: Henrik Nordstrom <hno@dont-contact.us>
Date: Mon, 07 Feb 2000 18:17:02 +0100

Marc-Adrian Napoli wrote:

> Ahh, so if i have a website that is being cached - and there is a certain
> jpg on the site that has been changed, but anyone going through the proxy
> gets the old version after X amount of times attempting to refresh - i'll
> need to change the refresh_pattern for the jpg mime type?

Or wait for one user to push that reload button (unless you are running
a accelerator or "transparent proxy", and the user uses IE, in which
case the reload button won't help).

The algorithm is pretty simple:

* Squid considers the object fresh for X% of the modification age when
the object was first requested.

So lets say an object was modified at 14:00, a user requested the object
(not yet in cached) at 16:00, then the objects modification age was 2
hours. The default configuration then says that an object is considered
fresh for 20% of it's modification age which is 24 minues, so if another
request arrives between 16:00 and 16:24 Squid will assume the object
isn't modified. If a request arrives at 16:25 (or later) then Squid will
first query the origin server to see if the object has been modified
(after which this all starts over again, with the object considered
fresh for 20% of it's modification age, which is a little bit longer
time if the object hasn't been modified..)

The percentage and upper limit is configured in refresh_pattern.

--
Henrik Nordstrom
Squid hacker
Received on Mon Feb 07 2000 - 14:05:13 MST

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