[Zope] SharedResource insight ?

[Paolo Bizzarri]

On Friday 23 July 2004 20:52, Dieter Maurer wrote:
> Paolo Bizzarri wrote at 2004-7-23 16:48 +0200:
> > ... transaction aware cache management ...
> >We are looking for some product to provide a cache shared between all
> >the threads in Zope, and I think we could use the SharedResource (see
> >http://www.dieter.handshake.de/pyprojects/zope/SharedResource.html) module
> >for such a purpose. This cache will mantain objects built from an SQL
> >database.
> >
> >However, we have some doubt regarding Zope transactions and cache
> >management.
> > ...
>
> Your doubts may be justified.
>
>   "SharedResource" is not transaction aware.
>
>   When a transaction puts something into the resource and
>   later aborts, it is is still in the "SharedResource".
>
>   Moreover, other transactions can see it before the changing
>   transaction commits.
>
> For many applications, this is not very problematic -- e.g.
> when you cache the result of SQL methods. Usually, such SQL methods
> put only committed changes into the cache (however, it is
> easy to construct application for which even this is not true).

> When you really need transaction awareness, it is probably best
> to put your cache into a mounted ZODB backed by e.g. a RAM storage --
> very similar to how Zope manages sessions nowadays.
> You can even use Zope's "temp_folder" for this purpose (put an
> appropriate BTree based (!) cache manacher into this folder).

We thought to use an object inside a temp_folder, containing, inside, whatever 
suitable structure (a dictionary, a BTree, etc.).

However, we thought that since temp_folder uses the LowConflictResolution, 
which does not support the conflict resolution, this was unsuitable.

Are we wrong?

-- 
Paolo Bizzarri - President - Icube S.r.l.
Address:   	Via Ridolfi 15 - 56124 Pisa (PI), Italy
E-mail:	p.bizzarri at icube.it	Web:	http://www.icube.it
Phone:	(+39) 050 97 02 07	Fax: 	(+39) 050 31 36 588