[Zope] Multiple Processes

[Michel Pelletier]

David Binger wrote:
> 
> What prevents id collisions in Zope?

An "Optimisitic Colision Resolution Protocol"

> It looks like the the ObjectManager.py code
> checks to see if the id is taken, and then
> it reserves the id.

Right.

> Is there a danger that 2 processes/threads
> (z2.py -t 4?) could both check and reserve
> the same id?

Yes.  One thread will win, and one thread will loose.  The winner will
get the new id.  The looser will try again.  The looser will find out
when it tries again the the id it wants is taken, and will report that
to the user.  The user picks another id.

> Is there something in Zope that prevents this
> (improbable, but perhaps possible) problem?

No, but a programatic resolution protocol is planned for future releases
of ZODB.

> 
> Is there certain way to find an
> object id that is not taken?

The chances of colision are very small unless you have an incredibly
write intensive application (which is not ideal for ZODB filestorage. 
In that case, you should store your information in a RDBMS).  This the
"optimism" in optimistic.

-Michel