Re: Update Delays

From: Ernst Heiri <>
Date: Mon, 28 Jul 1997 14:37:09 +0200

On Mon, 28 Jul 1997 17:59:46 +1000 (EST) Paul Black wrote:

> I think this is a question that gets asked a lot, anyway here goes:
> A user updates his homepage which is running on our Apache Http server.
> The user is using our squid cache (1.1-11) and he cannot see the changes he
> has made for a period of a couple of hours.

Please allow me to give you two answers:

1. Answer:
If a page is regularly updated (may be automatically generated) use a
metafile to set an expire header.
If it's a quasi static page the last modification header generated from
the last modifcation date of the file used is best choice.
> Is this the normal behavour of squid? Is there any config options which
> could be set to make squid accept the update a bit faster? I suspect if
> he was using netscape and used the control reload option he would see
> the new version of his page, but I dont want to have to tell thousands
> of users about this.

2. Answer:
There is no best solution for everybody!
If you will prevent that everybody gets allways the actual page there
is almost no caching possible (unless it's possible for you to set an exact
expires value for all your documents - but this is difficult in my opinion).

Users which can affort to have an exellent connectivity will not
risk to have ever a stale page - but they don't need to have a caching
proxy anyway ...

But there are people arround the world who can't afford Internet with
reasonable response times without using a caching proxy - they will
accept the risk to get some stale pages from time to time and to have to
press the reload bottom.
The staleness of an object is influenced by the refresh pattern rules
set by the cache manager using the last modification header.
There are no best refresh pattern too - there is for every organisation
a specific tradeoff between the risk to have some stale objects and the
risk to have long response times.


----------------- SWITCH Swiss Academic & Research Network ------------------
Ernst Heiri Voice: +41 1 268 1540 (direct: 1543)
SWITCH Head Office Fax : +41 1 268 1568
Limmatquai 138 Mail :
CH-8001 Zurich, Switzerland Mail : S=heiri;O=switch;P=switch;A=400net;C=ch;
Received on Mon Jul 28 1997 - 05:45:23 MDT

This archive was generated by hypermail pre-2.1.9 : Tue Dec 09 2003 - 16:35:51 MST