[Twisted-web] html cache with timeout

[Valentino Volonghi aka Dialtone]

On Wed, 2 Feb 2005 19:12:29 +0100, Andrea Arcangeli <andrea at cpushare.com> wrote:
> > t.cached(name=str(self.__class__)+IA(ctx).get('uid', ''), lifetime=10)[...]
> 
> Isn't that going to leak memory badly with tons of users seldom
> accessing the site? At least for my usage I can't do the above or it
> would risk to run my app out of memory.  lifetime isn't a timer, so
> it'll never be freed.

Since you are the one that is setting the cache this is actually not a problem at all. You can do

isLogged = IA(ctx).get('uid', None)
t.cached(name=str(self.__class__)+('1','0')[isLogged == False], lifetime=10)[..]

This won't leak anything except for logged/not logged users which is what you want.

Now it should be clear what are the advantages of being able to set the name yourself :).
 
> To get automatic garbage collection one should store it in the
> session, or at least attach a timer that fires indipendently if the
> rendering is enabled or not.

Just running the same thing that expires the sessions is enough. It's 5 lines of code or something like that, of course this should be left to the cache manager implementation.

> I'm using this only for the forms right now:
> 
> def renderCachedForms(ctx, lifetime=0, *args, **kwargs):
> 	return tags.cached(lifetime=lifetime,
> 			   name='formless-'+str(url.URL.fromContext(ctx)))[webform.renderForms(*args, **kwargs)]
> 
> It's very handy to use by just repalcing webform.renderForms() with
> renderCachedForms(ctx).

I think you can cache the result of self.docFactory.load() in the same way you put t.cached() in loader.stan()

> I still doubt it'll be as fast as httprender cache, but I can try.

from my tests it shouldn't be that slower. But  you do over 200 req/sec so it can be different.
 
> It has taken me minutes to enable httprender caching in the whole http
> site, so I tend to consider that API more handy, and peformance should
> be a bit higher too. So I don't see much point to use the stan cache in
> order to cache whole documents when the other lowlevel cache can be used
> in the rend.Page.

With this it should take a lot less.