[Zope-dev] Re: sessions in the presence of conflicts

[Florent Guillaume]

[Using zope-dev@ instead of zope@]

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

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Florent Guillaume, Nuxeo (Paris, France)   CTO, Director of R&D
+33 1 40 33 71 59   http://nuxeo.com   fg at nuxeo.com