[Zope-dev] [announce] for the CVS junkies: multiple ZODB mounting product.

[Shane Hathaway]

Anthony Baxter wrote:
> 
> I just bolted together from bits I scanned from CVS a 'MountedFileStorage'
> product. This allows you to use multiple ZODBs in a single Zope. It's
> something I've done "just for the hell of it" but thought that there
> might be other people out there who want to play with this stuff.
> 
> http://www.zope.org/Members/anthony/software/MountedFileStorage_hack/
> 
> It needs an up-to-date CVS.
> 
> As for why I've done this - I _really_ _really_ want multiple ZODB
> support - we have a couple of requirements for it. This was an excuse
> to fiddle and figure out how it works.

You did better than you think, Anthony.  I was going to release the
product I've been putting together, but your little product does
virtually the same thing.  Good work!

There is, however, a major security problem with making it so easy to
mount a FileStorage.  In my product, per Jim's suggestion I set it up
so that the user is required to create an External Method in order to
mount a database.  That actually makes things a little more flexible in
that it provides you the ability to mount things other than
FileStorages.

There are still some issues with mounted databases.  The primary issue
is that they interact strangely with ZClasses.  However, if you have
the same ZClass defined in both the primary database and the mounted
database, ZClasses seem to work fine.  (I wouldn't bet my company on
it, though.)

The other issues are that you can't easily undo nor manage mounted
databases.  That is more of a UI problem which could be solved by
product authors, however.  I envision a product that would create a
"mounted database manager" object.  Inside the database manager you
could add as many mount points as you want.  The database manager
object is where you would go to pack any of the mounted databases.

> Please don't run this on a Zope which hasn't got a backed-up copy of the
> Data.fs.

... And please report any problems which you may think are being caused
by the mount.  http://www.zope.org/Wikis is a mounted database and it's
running fine, but YMMV.

Shane