Re: Something about the caching feature in 0.9.x

Hi Philip,

Thank you! You are definitely right!
Now I do understand that whatever the server
answers I should take it as it is, and process
in consequence. I mean it's wiser to accept
that a given server doesn't want to provide
caching information about its content.

The question which seriously troubles me is:
Is it possible to have a server that returns
the same etag/last-modified data even if the
content has changed?

How should we handle that if it happens?

Karim
--
http://xhtml-css.com
Be Valid or die learning

On 11/15/07, Nikita The Spider The Spider <nikitathespider@gmail.com> wrote:
> On Nov 15, 2007 9:47 AM, Karim A. <directeur@gmail.com> wrote:
> >
> > I read here: http://validator.w3.org/todo.html
> > that in the 0.9.x series you'll start using Last-Modified
> > to cache validation results and request again only
> > if-modified-since.
> >
> > I'm very interested in that since the release of
> > our humble project http://xhtml-css.com
> > and I struggle with some say chaching "standards".
> > Not all servers provide "Last-Modified", some provide
> > "etag", other servers nothing and some others both![1]
>
> Hi Karim,
> Providing both is valid. According to the HTTP 1.1 spec, "[T]he
> preferred behavior for an HTTP/1.1 origin server is to send both a
> strong entity tag and a Last-Modified value."
> http://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html#sec13.3.4
>
> A server may also legitimately not send any cache information if it
> doesn't want its responses to be cached. When no cache information is
> sent, a strictly-complying user agent must assume that what it has in
> its cache is stale. In this case the UA can still use what is in its
> cache ("A client MAY also specify that it will accept stale
> responses...") and some browsers do so very aggresively to improve
> performance.
> http://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html#sec13.1.6
>
>
> > The best, of course, will be to use Last-Modified
> > and etag, but I'm not sure how reliable they are.
>
> Good news -- it isn't your job to decide how reliable they are. If the
> server sends out this information, your user agent must respect it or
> be in violation of RFC 2616. If the information looks odd (e.g. a
> Last-Modified date of 1 second ago along with an ETag that's the same
> as the one you saw one month ago), that's the business of the server
> admin. Caching is complicated enough without trying to second-guess
> what the server sends out. =)
>
> Good luck
>
> --
> Philip
> http://NikitaTheSpider.com/
> Whole-site HTML validation, link checking and more
>

Received on Thursday, 15 November 2007 18:49:33 UTC