Thank you Ian.
Likewise, this technique can also apply to almost any other kind of file
that doesn't normally accept arguments. Like *.CSS, *.JS or even plain old
*.HTML.
Cheers....
----- Original Message -----
From: "Ian Daniel" <[EMAIL PROTECTED]>
To: "Multiple recipients of list witango-talk" <[EMAIL PROTECTED]>
Sent: Monday, July 22, 2002 11:04 PM
Subject: RE: Witango-Talk: Caching Problems in General ... was IE caching
problem
> I concur with Scott's response ... that is exactly what we do in these
> cases, to guarantee that the browser actually calls the server.
>
> Ian
>
> -----Original Message-----
> From: Scott Cadillac
>
> Hi Garth,
>
> Do like Ian does with TAF files. When making a fresh call to the image -
to
> check that it made it - dynamically add an argument (to the filename)
that
> contains a unique value each time.
>
> Example:
>
> <img src="uploaded_images/emu.jpg?random=2349872394872" />
>
> MSIE believes it has to get a fresh copy because MSIE cache is typically
> based on the entire URL. Then IIS will serve up your image normally and
the
> arguments are ignored.
>
> Hope this helps. Cheers...
>
> ----- Original Message -----
> From: "Garth Penglase" <[EMAIL PROTECTED]>
> To: "Multiple recipients of list witango-talk" <[EMAIL PROTECTED]>
> Sent: Tuesday, July 23, 2002 10:18 AM
> Subject: RE: Witango-Talk: Caching Problems in General ... was IE caching
> problem
>
>
> > Another thought, regarding this...
> > Have unique URLS won't stop IE's aggressive caching of images though. A
> lot
> > of my caching problems are not the HTML code but images that are cached
> by IE.
> >
> > For example, a recent problem which still has me stumped is the case of
> an
> > admin system which includes a file upload process.
> >
> > The process entails a particular file being uploaded (say emu.jpg) and
> then
> > referenced by the following page (ie ubuys/emu.jpg) to display that the
> > image was successfully loaded. However, if the image changes, though
the
> > reference stays the same, the old image will still show, or if there
now
> is
> > no image, IE still shows that there is an image. Accordingly the admin
> > system is now "lying" to the administrators and they don't know what to
> > believe.
> >
> > Any ideas on how to get around this?
> > Garth
> >
> > At 11:25 22/07/02 -0700, you wrote:
> > >Good point, Robert .... always thinking ..
> > >
> > >Ian
> > >
> > >-----Original Message-----
> > >From: Robert Shubert
> > >
> > >Just an interesting note:
> > >
> > >The HASH function of T2K restricts output to 32 characters and it is
> > >therefore possible to create two identical HASHes with <@CIPHER
> > >action=hash str=<@CURRENTTIME>>.
> > >
> > >Another way of creating an ever increasing value is <@TSTOSECS
> > ><@CURRENTTIMESTAMP>><@TIMER> This value is ensured to be unique unless
> > >the same person is able to retrieve two pages in the same millisecond.
> > >Keep in mind that this only works if the CURRENTTIMESTAMP is ever
> > >increasing, if you adjust the time on the server (or adjust for
daylight
> > >savings) it could create duplication, although it's still highly
> > >unlikely.
> > >
> > >Bob Shubert
> > >Tronics
> > >
> > > > Ian Daniel wrote:
> > > >
> > > > Hey Garth:
> > > >
> > > > We experienced great caching issues which would not all be solved
> > > > using the approach described below. Remember that cache involves
> > > > multiple versions and schemes of browsers, proxy servers,
firewalls,
> > > > network routers and servers.
> > > >
> > > > In my experience, the only way to "beat them all" in one action is
to
> > > > ensure that every URL is unique.
> > > >
> > > > For dynamically-generated pages, we append what we call a
"no-cache"
> > > > argument to every URL. At NCOL, we have standardized on a hash of
> the
> > > > currenttimestamp, like so:
> > > >
> > > > &_nc=<@CIPHER action=hash str=<@CURRENTTIME>>
> > > >
> > > > For statically-generated pages, we add a large random number,
> > > > generated in JavaScript, to ensure that every browser display (even
> > > > those presented by the browser back button) has a unique URL.
There
> > > > are several ways to do this. We usually use:
> > > >
> > > > <script language="javascript">document.write('<a
href="whatever.taf?'
> > > > + Math.round(Math.random()*1000000000) + '">Your Link
> > > > Here</a>')</script>
> > >
>
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