[Zope] Strange session behavior [EXPLAINED]

[Andrew Athan]

For those of you who are experiencing sessioning issues, I wanted to
report back to the list on my findings:

Very strange things can and will begin to happen if you refer to
sessions within your standard_error_message, or within any "top level"
exception handling code registered with Zope.

The cause seems to be in Publish.py.  It does an abort(freeme=1) prior
to calling the exception handler.  This means the exception handler runs
outside any transaction (as in, Transaction.py).

Apparently this hoses the session machinery, presumably because the
index[] and data[] structures are no longer guaranteed to be
synchronized to each other (as they are at transaction boundaries).

So, to avoid problems, do not refer to session variables within your
standard_error_message.

The Zope folks are looking at this abort() call; the verdict is out on
whether calling abort(freeme=1) before exception handlers are invoked is
a bug.

Andrew (I've got the bends from diving so deep) Athan

PS:  I'll be putting various Zope/Python goodies at www.memeplex.com