[Zope-dev] _v_ and ZEO

[Florent Guillaume]

Toby Dickenson  <tdickenson@geminidataloggers.com> wrote:
> > Whenever a write comes in at the over-ten-second mark, 
> >you write the _v_ attribute to the persistent attribute. 
> 
> That would be bad. _v_ attributes are lost when the object is
> deactivated and removed from the ZODB memory cache.... It would lose
> the majority of counts for all the most frequently accessed counters.

This reminds me of a question I had: given that (from what I understand)
_v_ attributes only live in the object cache of a given Zope, what
happens with ZEO if a product uses _v_ attributes (with a timeout) as a
cache to avoid going to an slower database ?

Here I'm thinking specifically of LDAPUserFolder. Suppose a user hits
ZEOclient1, which caches in _v_* his info. Then the same user hits
ZEOclient2 and changes some info in LDAP. This new info is cached on
ZEOclient2. When the user goes back to ZEOclient1, he will see old data.

Or am I misunderstanding something ? My question really relates to any
use of _v_ as a cache that can survive on publisher transaction, really.
Should _v_ never be used like that ?

Florent

-- 
Florent Guillaume, Nuxeo (Paris, France)
+33 1 40 33 79 87  http://nuxeo.com  mailto:fg@nuxeo.com