[Zope] Re: Zeo and conflict resolution (was "suddenly confused")
ric at digitalmarbles.com
Wed Jan 30 17:31:14 EST 2008
On Jan 30, 2008, at 1:39 PM, Chris McDonough wrote:
> Ricardo Newbery wrote:
>> On Jan 30, 2008, at 12:59 PM, Tres Seaver wrote:
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>>> Ricardo Newbery wrote:
>>>> Has anyone given thought to maybe providing a more general class
>>>> conflict resolution in the core distribution? The Length class
>>>> for simple counters and I guess it can also be used for just simple
>>>> assignments, but what about something more complicated, perhaps
>>>> some sort of factory defined at the moment of instantiation?
>>>> Assuming this is even possible, having such a general purpose
>>>> conflict resolution class defined in the Zope products directory
>>>> might make it easier to distribute a third-party product that
>>>> needs a
>>>> little conflict resolution. Just a thought.
>>> Custom CR code is *hard* to get right: most people would be
>>> better off
>>> using stock code (e.g., on of the tree types defined in the BTrees
>>> package, or Length). Those who can get it right aren't likely to
>>> their hands held. ;)
>> I meant easier for the end user, not the developer. It's kind of
>> complicated right now to explain how to set up a ZEO configuration
>> to work with your third-party product. Makes it a bit of hurdle
>> to distribute such a thing for general use.
>> Oops, I just realized that Length won't work for simple
>> assignments as the conflict resolution assumes it's trying to
>> resolve a counter (which should have been obvious, I know). Is
>> there zope core class I can use for a simple assignment, that
>> maybe resolves conflicts by just picking the last value assigned?
> There is no such thing as the "last value" during a conflict (only
> three states: what's in the database, and the two conflicting
> states: what connection1 says, and what connection2 says). If the
> values are always going to have a __cmp__ method or if they can be
> otherwise compared (like integers), and if you're willing to accept
> the "highest" of the three states, you might use the conflict
> resolution policy of Products.Transience.Transience.py.Increaser.
Great, that's exactly what I need. Thanks.
I also noticed another interesting option for a counter at
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