Re: Last-Modified vs. Expires

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The default is .html is static, and the admin has to enable .shtml
(or whatever extension they want) to get mod_include to start working.
mod_include's default is no Last-Modified. You have to enable XBitHack
full and chmod g+x the files to get Last-Modified.

Anything else would require two passes over the input -- which hurts
performance. However there might be some cute tricks we can pull... hmm.
I've got two speed improvements for mod_include on The List anyhow
(boyer-moore search for the <!--#, and use mmap()), with those in hand I
could really see making the default do two passes over the input. Then
not only would you get Last-Modified on truly static content, but I could
also generate a Content-Length.

There is no default Expires, but I can propose one, I'm not sure how
successful I'll be. What would be a good length?

BTW, MSIE 4.0b2 has preliminary HTTP/1.1 support. It has some bugs (visit
http://www.arctic.org/~dgaudet/ap13docs/misc/known_client_problems.html
for a list of all the client problems we've worked around). But they are
supporting HTTP/1.1 ETags, which is another validation mechanism.

Dean

P.S. And I don't envy you folks the task of HTTP/1.1 proxy implementation.
It's a huge job from what I see.

On Tue, 22 Jul 1997, Ernst Heiri wrote:

>
> On Mon, 21 Jul 97 15:11:51 -0700 Duane Wessels wrote:
>
> > dgaudet@arctic.org writes:
> >
> > >Hi folks, this may be a bit off-topic.
> > >
> > >I'm trying to decide on how to weight some additions to features in Apache
> > >which assist in generating Last-Modified headers for dynamic html content.
> > >Others in the group argue that it's better to just use mod_expires and
> > >generate Expires: headers than it is to try to get a sane Last-Modified
> > >header.
>
> The SSI mechanisme of Apache is used mostly for including *static* files but
> the result looks like a dynamic page to the proxy with no Last-Modified
> and no Expires (if Expires is not explicitly configured by the webmaster).
> BTW: On our webserver *every* (static) page uses SSI.
>
> If this is the default behavior of Apache, a lot of static pages on the web
> look like dynamic pages and will not be cached by any proxy anymore.
>
> > >I'm curious, what works better with squid?
> >
> > I think Expires would be preferable, and especially
> > if you can get long Expires values (e.g. days instead of minutes).
>
> Ok we could use Expires (instead of Last Modified) but only if it's possible
> that Apache sends per *default* reasonable Expires for all objects.
> (with default I mean with its standard configuration.)
>
> Duane, my argumentation are driven by my experience as webmaster *and*
> proxy manager in a real world environment:
> Technically I agree that Expires is the better mechanisme than Last-Modified
> but if we expect that a majority of webserver will not be configured
> to set a reasonable Expires it's much better to use Last-Modifed for
> SSI-documents which are not dynamic.
>
> Ernst
>
>
>
>

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Received on Tue Jul 29 2003 - 13:15:42 MDT