[Zope] Question on: How-To: When Cookies won't do it

[Johan Carlsson]

> >   I browsed trough the How-To: When Cookies won't do it
> >   and I have some questions.
> >
> >   How much speed do you really gain from using file for
> >   data marshaling?
> >
> >   Would it be a good idea to use Object Pooling (pre created
> >   objects) to speed up a session object solution?
> >
> >   The reason I don't like the file based solution is that
> >   I won't scale with ZEO but a Object solution would, right?
> >   There would also be possible for cool stuff like session
> >   failover and long time session (much list version but individual
> >   and perhaps with a limited scoop)
> >
> >   Another reason is that I like the concept of the ZODB,
> >   why think in a non ZODB way?
> 
> One word: Transactions.
> 
> Every change to a ZODB persistent object causes another transaction to be 
> written to storage. A busy site with lots of sessions will cause the 
> Data.fs file to grow at quite a rate. Pavlos choose this solution 
> to avoid 
> this growth.
> 
> I suggested trying to use a seperate instance of the ZODB, using 
> MemoryStorage, so that all session objects would be in memory. This could 
> then maybe be extended to support ZEO as well, but I haven't really dived 
> into that yet.

Ok.
One (or more:) question(s).

- When does filestorage or rdbm-storage write to disk? 

- Why can't the session object rely on the ZODB memory cache.
  They are (for the most) fast deployed objects. 
  Maybe even use _v_ objects (which would be automatically destroyed).

- How does transactions slow down the process, and how are
  transactions connected to storage (in this situation)?


Transaction support for sessions are one of the things you
really want. I even been thinking about using private versions
for sessions, for instance in a e-shop you would be able to 
customize your order directly in the OLAP-system but within a
version. Not until you commit your transaction the changes 
gets propagated to the OLAP-system.

Regards,
//johan