[Zope-Coders] Persistent Sessions question

[Shane Hathaway]

Evan Simpson wrote:
> This is primarily a question for Chris, but please chime in if you're 
> familiar with <ominous echo>Mounting Databases</ominous echo>.

Funny you should ask.  I've just created a product for a customer called 
DBTab.  It lets you mount databases (including ZEO) using a simple 
configuration file, similar to /etc/fstab.  Works great so far.

I've been holding off on releasing it publically because the ZConfig 
work will probably change the configuration file format.  But does 
anyone really mind having to rewrite a few lines in their config files 
sometime down the road?  Since I'm giving prior warning, I think no one 
can complain. :-)

> Having done all this, I created a Transient Object Container in the 
> MountedFolder and set expiration to about a week.  I pointed my Session 
> Data Manager at the new container, and everything *seems* to work as 
> planned.

It should work, although there's a bug in ZODB/Mount.py: long-running 
transactions that work on lots of ZODB objects can exhaust all the 
available mounted connections, resulting in a deadlock which is likely 
to eventually deadlock all other ZODB threads as well.  DBTab fixes this 
(it does not use ZODB/Mount.py).  I haven't found a good way to fix it 
in ZODB/Mount.py.

Shane