Ok I've dug deeper and now understand the problem. The root cause is
in the multi-databases support.
The problem is that the Zope startup only closes the main connection
it had on the root database. The first connection to the
TemporaryStorage, created and opened during Zope startup, is never
closed, so still is a synchronizer in its original transaction, but
is nevertheless reused in other transactins, without a proper
synchronizer set up.
When a MountedObject needs to be traversed, it tries to find an
existing connection for the new database by doing:
conn = anyjar.get_connection(db_name)
where anyjar is the "parent" connection. If there's a linked
connection for that database, it's returned, otherwise if the multi-
database already has seen the wanted database, it opens a connection
from it, then adds it to the "linked" connections attribute
(conn.connections) and shares this attribute between the two
connections.
I that fails, because the connection has never been linked to the new
database (which is the case during startup code), then the
MountedObject code does:
conn = self._getDB().open()
Here _getDB() correctly returns a newly instanciated database, which
has been linked to the other ones in the multi-databases setup
(shared "databases" dictionnary attribute, ultimately coming from
Zope2.Startup.datatypes.DBTab.databases).
Then open() returns a new opened connection for that database. *BUT*
this new connection is not "linked" to the others (using
their .connections attribute). This code from get_connections is needed:
self.connections.update(new_con.connections)
new_con.connections = self.connections
which would be written, in the context of code executing in
MountedObject (in _getMountedConnection):
except KeyError:
conn = self._getDB().open()
anyjar.connections.update(conn.connections)
conn.connections = anyjar.connections
return conn
But of course really this code doesn't belong to MountedObject. This
is just the simplest way I could find, if others want to test it.
The ".connections" sharing is really funky, apparently all the
connections opened in the context of the same multi-databases support
are intended to be present in it. Why is this access not indirected
through the multi-databases support in DB itself? Also I don't
understand why open()'s "delegate" attribute is not stored as a
connection attribute, and close() should reuse it instead of obeying
a "primary" attribute. Anyway, I guess historical code, etc.
I'll let specialistst of the multi-databases decide what to do :)
Florent
--
Florent Guillaume, Nuxeo (Paris, France) Director of R&D
+33 1 40 33 71 59 http://nuxeo.com [EMAIL PROTECTED]
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