Re: refresh_pattern?

From: Henrik Nordstrom <>
Date: Thu, 23 Jul 1998 22:19:08 +0200

Katariina* wrote:

> so what is percent for?

When the age is in between min and max age, and the origin server told
us when the object was last modified.

We can then assume that a object that has not changed in a long time is
less likely to change than one that changed a short time ago.

> but if the object was 1000 minutes old when we got it
> from the server then the LM_FACTOR will be bigger than
> the percent after 20000 minutes and till that time squid will
> return FRESH.

No. The percent are percent of the time since the object was last
modified. The max age sets a upper limit.

The default "0 20% 4320" says:
1. If the object was changed "now", then always revalidate.
2. If the object is older than 3 days, than always revalidate.
3. If the object was modified in less than 15 days ago, then revalidate
when the object is cached longer than LM_FACTOR*time-since-modification.

So if the object was changed 10 minutes ago, then revalidate the object
if it has been cached for 2 minutes. If it was changed 5 days ago then
revalidate if it has been cached for 1 day.

> well to my opinion old pages have more chance to get
> updated than pages updated 10 minutes ago!

Then you assume that most web contents are changing with a period
shorter than 10 minutes, even if older than 10 minutes... don't make
sense do it?

Today most web content divided into three categories:
1 Static objects that rarely gets updated
2 Dynamic pages that are not cacheable
3 Periodically changing pages

> but squid is thinking that old pages are less updated
> if I understood right...

Yes. Squid assumes that objects that has not been changed for a longer
period of time is less likely to change close in the future.

> also there it says that
> CLIENT_MAX_AGE and EXPIRES are may I set squid
> to not to check them???

Client set max age can't currently be overridden.

Expires is currently overridden when you set the min age.

Henrik Nordström
Sparetime Squid Hacker
Received on Thu Jul 23 1998 - 13:33:43 MDT

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