[Zope-dev] Mountpoints

[Tim Peters]

[Chris McDonough]
> There is a wrinkle about performing this merge that eluded my memory
> until now.
>
> To support multidatabases within Zope, it was reasonable to change
> ZODB.config.ZODBDatabase to support the heretofore
> likely-unused-by-real-world-code "databases" and "database_name" options
> that may now be passed into ZODB.DB's constructor:
>
> http://svn.zope.org/ZODB/branches/blob-merge-branch/src/ZODB/config.py?rev=38626&r1=38574&r2=38626
>
> The current blob-merge-branch code depends on this change being
> available in the ZODB revision it uses.  In case you're interested, the
> code that actually makes use of this feature in the zodb-blobs-branch is
> in the Zope2.datatypes.DBTab.getDatabase method.
>
> Is this change acceptable for a merge into the ZODB HEAD?

Turns out that a release of Zope3 has already been made that supports
multidatabases, and I'd naturally prefer to follow the lead of a Zope
that's already out there.  Jim showed me the Zope3 implementation code
and an example today.  I found the code easily (on Zope3 trunk), but
can't for the life of me find anything there that looks like his
example.  Jim, where is that?

The Zope3 code in question is in

    src/zope/app/appsetup/appsetup.py

function multi_database().  Note that they didn't change any ZODB
files, instead they give values to a DB's .databases and
.database_name attributes after constructing the DB.  While that might
be questionable in general <cough>, the implementation of
multidatabases was meant to be both concrete and public.  It's not an
accident that ZODB's tutorial tests/multidb.txt doctest explains and
exploits details of the concrete implementation -- it's not meant to
be abstract.  IOW, poking in new values for these attributes isn't
considered to be evil.

I believe (here's where the example I can't find would nail it) they
use the name on a <zodb> section as the DB's database_name.  Fred
points out that ZConfig section names are case-insensitive, forced to
lowercase, so that

    <zodb CHRIS>

and

    <zodb cHris>

have the same name.  That's not ideal, and threading these attributes
throughout ZODB's config.py instead (as you did) would be a sane way
to worm around that.

But for right now, I think doing it differently than Zope3 does it
would cause needless confusion more than it would help.  Enhancing
Zope3 and Zope 2.9 in the same way(s) here could make sense.

Some mechanics:  if we do need to make changes, ya, ZODB trunk is the
place to do it.  Work on the branch should use ZODB trunk now.  When
that's as ready to go as it's going to get, let me know and I'll make
"an internal release" of ZODB 3.6 so we can use a ZODB tag before
merging into Zope trunk.  ("An internal release" just means I update
ZODB's NEWS.txt, fiddle version numbers and dates in umpteen places,
and make a tag so other projects can use that -- it's the tag that's
important here; an internal release does not involve making tarballs,
Windows installers, announcements (etc), so it's much cheaper and goes
much faster (minutes vs hours) than making a public release.)