Dennis Allison wrote:
The issue here has had to do with session variables and their iteraction
with the persistence mechanism and conflicts and multiple threads for the
same session.  Chris McDonough has pointed out that session variables can
cause writes and write conflicts even if the only Zope level access is a
read.


Indeed, they have to track expirey and the like. This is why "sessions are evil" (tm)

I thought MVCC works out of the box for Zope 2.8.4 which uses ZODB
2.3.4. Am I wrong?

Nope, it works fine, we've seen all our read conflicts go away :-)

Sorry, I wasn't all that clear when I had my epiphany about REQUEST and
transactions.  You said it much more clearly and precisely.  Since
conflict errors are discovered and managed when the publisher commits,
there is not a whole lot one can do, in terms of code organization, to
minimize the potential for conflicts.

Oh, there's plenty, I can assure you ;-)

Ditching your frames is the 1st place I'd start... any scenario where several frames/iframes/whatever try to manipulate the same session variable (ie: per user) is doomed to failure ;-)

cheers,

Chris

--
Simplistix - Content Management, Zope & Python Consulting
           - http://www.simplistix.co.uk

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