Code would be good.

Note that changing the transientobject conflict resolution algorithm won't get rid of all write conflict errors, because the BTree-based indexes in the transient object container will still conflict during a "bucket split" and other situations that I can't exactly recall (they're documented in the BTrees source code). In fact, before you spend a lot of time tuning the TO conflict resolution algorithm, you should make sure that the majority of conflicts you're seeing do indeed come out of attempting to resolve conflicting transientobject states (as per the conflict error traceback). Conflict resolution algorithms are difficult and any algorithm will have DWIM-y tradeoffs, so it's useful to keep it as simple as possible.

Note also that if you store your session data in a ZEO server in order to do *any* transience write conflict resolution, the ZEO server process needs to have Products.Transience on its PYTHONPATH (as it needs access to the resolution code).

You also still haven't told us if you've tuned any of the knobs that I recommended you tune, so if you haven't, do that first. ;-)

- C

On Dec 15, 2005, at 5:35 AM, Florent Guillaume wrote:

[Using zope-dev@ instead of [EMAIL PROTECTED]

Dennis Allison wrote:
A more session-friendly conflict resolution might use:
1. if any of the states are invalid (that is, has a key '_invalid')
       return the invalid state.
   2.  if any any of the states attributes ['token','id','_created']
differ then there is a conflict, raise the conflict exception. 3. order the newState and savedState by modification time (or if that cannot be computed, by access time). 4. any key appearing in oldState's dictionary but not appearing in both savedState and newState should be removed from all. This corresponds to a key-value pair being deleted in one of the transactions. Insertions will be managed automatically by the updates. 5. beginning with the oldest, update oldState dictionary of key-value pairs using the dictionary part of newState and savedState. Return oldState.
This does several things.  First, it captures independent key-value
changes made in both potentially conflicting transactions. Second, it
provides a reasonable ordering for multiple (potentially conflicting)
key-value pair updates. Third, it manages insertions and deletions to the
session variable set in the presence of conflicts.
Does this make sense?  I have yet to figure out how to map a
TransientObject "state" back to the object it represents, but it clearly
is possible.

I certainly makes sense from a high level description, but the devil is in the details. I'd be interested in looking at it if you code something.


Florent Guillaume, Nuxeo (Paris, France)   CTO, Director of R&D
+33 1 40 33 71 59   [EMAIL PROTECTED]
Zope-Dev maillist  -
**  No cross posts or HTML encoding!  **
(Related lists - )

For more information about ZODB, see the ZODB Wiki:

ZODB-Dev mailing list  -

Reply via email to