[Zope-dev] MountedFileStorage

[Shane Hathaway]

Steve Alexander wrote:
> 
> I've just been trying out the MountedFileStorage product (by Anthony
> Baxter) with Zope 2.3.
> 
> I've got it mostly working, by patching a couple of typos, and making
> the SubApplication class derive from Traversable before Application.
> 
> I've *almost* got ZClasses defined in the root storage working in a
> mounted storage, but there are still a few issues there.
> 
> What product is DC using for the mounted storages on zope.org? Can I get
> a copy of it?

http://www.zope.org/Members/hathawsh/ExternalMount

ExternalMount is simpler and more flexible than MountedFileStorage. 
However, a feature of MountedFileStorage is that it lets you try to
mount the root of a ZODB.  For various reasons, that is a Bad Idea. 
That's why it has all the "subapplication" stuff, which ExternalMount
doesn't need because it won't let you mount the root of a ZODB.

Instead, you mount a subobject.  The application object in Wikis.fs on
zope.org contains a folder called "Wikis".  That folder is what gets
mounted; whatever else is in Wikis.fs (like a Control_Panel, an
acl_users, etc) is ignored.

I think you'll find that if you set up your mounted databases this way,
you'll get the reliability you're looking for.

> I don't see any undo records for objects in the mounted storage. It is a
> FileStorage, so I reckon they should be there.

Currently, undo and mounted databases don't mix.  You can only undo
transactions on the root database.  Besides that, there's the problem of
coordinating the undo of transactions that span multiple
databases--should it be done and how?

Mounted databases are interesting and, for the most part, robust, but
they aren't fully integrated with some of Zope's capabilities yet.

Shane