Ok, I narrowed the problem a bit:
In py4web/core.py, around line 207, there is this adjustment in order to
make some variables threadsafe:
# make sure some variables in pydal are thread safe
for _ in ['readable', 'writable', 'default', 'update', 'requires']:
setattr(pydal.DAL.Field, _, threadsafevariable.ThreadSafeVariable())
Turns out that PyDAL's _enable_record_versioning(), in order to create the
archive table, clones all original fields with their properties. Or, at
least, it tries to: it seems that copy() fails to correctly transfer
threadsafevariable informations when dealing with those variables.
I guess that when cloned field's requires attribute is accessed those
information are not valid anymore and py4web throws the aforementioned
exception.
I was able to circumvent this error adding an explicit copy of the
attribute in pydal, but still I'm not sure if this could eventually lead to
thread problems:
for field in self:
nfk = same_db or not field.type.startswith('reference')
clone = field.clone(unique=False, type=field.type if nfk else 'bigint')
clone.requires = copy.copy(field.requires)
clones.append(
clone
)
Any thougths?
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