[Lispweb] Mod_lisp 2.0 released

Marc Battyani marc.battyani at fractalconcept.com
Tue Jun 19 15:27:04 CDT 2001


Daniel Barlow writes:

> > The model has some concrete advantages:
> >
> [...]
>
> As long as we're discussing the general approach:
>
> 8.  Dynamic but infrequently changing content can be cached by the
> front-end webserver and future requests for the same page served
> directly by it (using sendfile() or mmap() or something fast) without
> having to involve Lisp - or involve Lisp only to ask "has this page
> changed since {n}"
>
> This is something that mod_lisp could score a significant win on if it
> also added a cache control protocol so that Lisp could tell it to
> discard outdated pages whenever it needed to.  You can do a certain
> amount with mod_proxy (it claims, though I've never actually managed
> to persuade it to do so in the real world) by setting appropriate HTTP
> headers (Last-Modified, Expires, etc) and correctly handling
> conditional GETs in your backend server.  But it would still be a lot
> neater if you could control page flushing from the Lisp side instead
> of the frontend having to poll.

Good idea. But the cached data has to be managed by the Lisp process so that
it will work with URI session encoding which gives problems to cache
managers.
For instance, when I connect to the mod_lisp page I get redirected to an URI
like
http://test.fractalconcept.com/asp/sdataQIEcRwW0ZHW9DQjsCbq_/sdataQucECuqhCs
SGnNjI where the base64 code the session id and other data. If somebody else
go to the same page he will have a different URI.

So it could be interesting to have a caching prootocol between Lisp and
Apache like:

mod_lisp to Lisp: give me /asp/sdataQIEcRwW0ZHW9DQjsCbq
Lisp to mod_lisp: ok here it is, please cache it for 600 seconds with name
"cached-data1"  + <data>

mod_lisp to Lisp: give me /asp/sdataW9DQjsCbqQIEcRwW0ZH
Lisp to mod_lisp: use "cached-data154"


mod_lisp to Lisp: give me /asp/sdataCbqQIEcRQjswWW9D0ZH
Lisp to mod_lisp: use "cached-data154"
mod_lisp to Lisp: I don't have "cached-data154", give me
/asp/sdataCbqQIEcRQjswWW9D0ZH
Lisp to mod_lisp: ok here it is, please cache it for 600 seconds with name
"cached-data1455"  + <data>

It's just an ideas not a real protocol but it could work.

Marc





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