[Techtalk] caching and apache2

Caroline Johnston johnston at biochemistry.ucl.ac.uk
Thu Jul 13 18:18:10 UTC 2006

thanks Almut! Wasn't at all RTFM, was actually quite helpful. I'd given up
googling because I didn't know what I was looking for. I had another look
when I got your mail and eventually discovered that you can mix html and
svg in the same xml doc with namespaces. I didn't know that was possible.
It avoids the iframe caching problem altogether and means you can pretty
much just dump pictures anywhere in your html. Probably everyone else knew
this already, but it's all new and exciting to me. I can see me
spending all evening making small shapes bounce across my browser ;)


On Wed, 12 Jul 2006, Almut Behrens wrote:

> On Wed, Jul 12, 2006 at 06:59:53PM +0100, Caroline Johnston wrote:
> >
> > I've managed to get this working now, but I'm hitting problems
> > with pages in iframes. Basically, I have some svg files that are changed
> > often. They can be <embed>ed or <iframe>d in an html page. When I access
> > the svg files directly, they don't cache, but when I access the parent
> > page, unless the url changes it doesn't reload the svg file. I've managed
> > to work around it because the parent file is actually dynamically
> > generated, so I can add a ?param=somerandomvalue to the end of the iframe
> > src url, but it seems a bit clunky. Am open to suggestions for a nicer way
> > of doing this?
> ahh, browser caching... This has already driven a number of people
> close to insanity ;)  Considering the big mess this whole caching issue
> is (getting better, though), your "workaround" seems like a rather
> elegant solution.  At least, it should work on any browser which is not
> entirely broken...
> In case you still want to play around with alternative approaches, just
> a few random pointers here.  My apologies, if this sounds RTFM-like --
> I promise, it's not meant that way. It's just that I'm a bit in a hurry
> at the moment...
> For one, it's good to know what the theory says; e.g., for HTTP/1.1:
> http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.9 .
> There are a number of similar caching directives for slightly different
> purposes. But maybe, you've perused this stuff already.
> Then, there's also the related Expires, ETag, etc. headers...
> Generally, many of those are HTTP/1.1 only, so make sure that's
> actually what the browser/webserver is talking.  BTW, is this a direct
> browser-to-webserver connection, or are there any proxies in between?
> Although the w3 document makes frequent use of the word "MUST",
> real-world implementations sometimes interpret those things as if
> they were more of an advisory nature...  So, trial and error often is
> the only sensible approach here.
> There's a neat page to test client caching features and behaviour:
> http://www.mnot.net/javascript/xmlhttprequest/cache.html
> For some additional ideas also see the related blog entry
> http://www.mnot.net/blog/2006/05/11/browser_caching
> And, if it comforts you to see that other people are having similar
> problems, just google for "iframe caching" :) -- you might even come
> across one or the other interesting suggestion...
> Good luck,
> Almut
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