Re: RE: [squid-users] adaptive refresh..

From: Klavs Klavsen <>
Date: Wed, 7 Nov 2001 10:57:44 +0100




> My boss, just discovered CacheFlow.. it's a cool lean, mean fighting
> machine.. but so is squid I tell him..

Sure squid is :)

> he's ready to let the two be set up, so we can compare their
> price/performance..
> Here's my problem.. I have set up squid 2.5 as an accelerator
> box (with the
> rproxy.patch)..
> but here comes my problem, in comparison with the cacheflow box..
> the cacheflow box, can be set up to refresh object's in the
> cache initially
> every 20 secs.. and then
> it adaptively - based upon how often the object actually
> changes it sets
> another refresh-rate.. thus saving
> capacity on the backend server..

see refresh_pattern.

Something I'd do is like (completely, utterly untested)

refresh_pattern jsp 0 0% 0
refresh_pattern html? 0 100% 10080
refresh_pattern jpg 1 100% 1440

etc etc.

format: "refresh_pattern" <regexp> <forced-valid> <percentage> <max-valid>

In this case the regexps are simple enough. The first line forces all
content to be always re-fetched each time. The second says "html is
fresh unless expressely reloaded for at most its age, and in any case not
more than 1 week", the third says "jpegs are valid for at least a minute,
most their age, up to a day".

KTK>this requires the server to state some sort of refresh-time?
KTK>the smart thing about the CacheFlow is that it sets
KTK>the refresh-time diffrently for every object - much more
KTK>detailed than any regexp pattern I could set..

The algo is very clearly explained in squid.conf, and is WAY more
than anything CacheFlow has to offer. Only "disadvantage", the resolution
in minutes, not seconds.
KTK> I get that.. 1 min. delay at min. - is ok.
KTK> it's just that when you have many objects, I don't want to have to
refresh them
KTK> all every minute - only the ones, that are often changed.. that's what
KTK> gives me.. without having to change code on the origin-servers.
KTK> as I see it, this should save requests between cache and

> This is the setup I have to compete with.. on squid, I can only set an
> update interval - to min. 1 minute.. -
> and I have journalists who updates somethings.. often.. and
> somethings not
> so often.. and they ofcourse want the changes
> to go on the site ASAP.. this is where the adaptive refresh
> is good.. cause
> perhaps they have to wait up to 5 min.. the first time,
> they change a page, after a longer time.. but the next time
> they change
> something, the adaptive refresh has lowered the time-between-refresh
> on that object.. while maintaining the higher
> time-between-refresh on the
> rest of the objects..
> This does save a lot of capacity, as old - never updated pages,
> automatically gets refreshed less often..

Just Ctrl-R (Ctrl-F5 in IE) while looking at that page, and anybody can
force a refresh for anybody.
KTK> and I don't want that.. cause then pages would be refreshed very
KTK> as we deliver news, many clients actually leave the page open, and
KTK> Ctrl+F5 in their browser to see if there are any new news..
KTK> Is it possible to set which IP's can force a reload via Ctrl+F5?

Received on Wed Nov 07 2001 - 02:58:17 MST

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