Re: Musings

G'day All!

On Dec 13, 12:20pm, Kevin Littlejohn wrote:
> Subject: Musings
>
> The default squid.conf sets the expiry time for pages to 3 days. If this
> default is lowered drastically, say to 12 hours, we're trying to predict
> what the results would be. As far as we can work out, it's going to
> depend on the makeup of the requests. If the cache is made up primarily
> of pages that are hit by many people (eg. msn.com), then this would mean a
> small number of pages would be refreshed 6 times as often, generating not
> too much extra traffic (and it's primarily our inbound traffic that I'm
> looking at here), and a lot of pages that are access say once every couple
> of days would no longer be cached
> (no big deal if they're only being accessed every couple of days anyway).
>
> On the other hand, if the cache is made up of lots of pages that are hit
> once a day only, then we're going to loose most of the cache, and most of
> the benefit of the server.

The problem with the example that you give above is that the server sends a
header to Squid telling it to not cache the page at all. They actually send
three headers to that effect, just to make sure I guess :(( (Not only that,
msn.com sends the whole content as the reply to a HEAD request).

A 'best practise' is for the server to send a realistic Expires: header. Most
of the big sites are setup to deny caching, so as to improve the number of hits
they recieve.

HEAD /default.asp HTTP/1.0

HTTP/1.0 200 OK
Date: Fri, 13 Dec 1996 04:49:20 GMT
Server: Microsoft-Internet-Information-Server/1.0
Cache-Control: no-cache
Set-Cookie: MSN2.0Splash=2; expires=Sat, 13 Dec 1997 04:49:20 GMT; path=/;
domain=.msn.com
Pragma: no-cache
Expires: Fri, 13 Dec 1996 04:49:20 GMT
Content-Length: 3243
Content-Type: text/html

To overcome this 'problem' upgrade to Squid-1.1.0 and increase the
refresh_patter min value from 0.

Constructive critisism to msn.com and friends about the appropriate use of
headers would probably fall on deaf ears.

Later
Ed

-- 
Ed Knowles aka Jasper				   Phone : +61 2 9385 4962
E-mail: ed@fatboy.geog.unsw.edu.au	           Fax   : +61 2 9313 7878
            What I lack in morals I make up for in principles.