[Twisted-Python] A proposal for simple remote object editing (Twisted and ZODB integration)

Robert Gravina robert at gravina.com
Tue Jun 27 14:31:56 EDT 2006

I'd just like to throw out an idea after working with Twisted  
(especially Perspective Broker) getting the early stages of my  
application going over the last few weeks.

I love object databases... I've been using ZODB because it's so  
simple to work with, no SQL, just create your Python classes and all  
their attributes (dictionaries, references to other objects) will be  
pickled for you and saved in a file (or database, never tried it  

Anyhow, I've started writing my Twisted application, where clients  
contact a server to get objects, edit their details, and send them  
back. Because ZODB works by maintaining references to other objects,  
I can't just replace them with the new Copyables  when they come back  
because they are different instances. So, I compare the _p_oid  
attribute (object ID) with my original objects to locate the one I'm  
looking for, copy the __dict__ across from the Copyable to the  
original object, and commit the transaction. I haven't gotten much  
further than that, but I'm sure I'll have problems with objects which  
refer to other objects etc.

What's great about Referenceables is that Twisted gives you the  
original instance when they come back to you, but the client can't  
access the attributes or run any of it's methods locally. What's  
great about Copyables is that the whole instance is sent down the  
wire and the client can alter it's attributes, call it's methods, and  
send it back...

Back to the ZODB... what would be extremely useful is if clients  
could get an objects from the ZODB sent down to them, edit the  
attributes and call the methods, and sent it back and *have it be the  
original instance again*. Sort of like the best of both words of  
Referenceables and Copyables. Of course, this doesn't have to have  
anything to do with the ZODB, it was just my motivation for this  
idea. Any object could be sent down the wire, edited, and sent back  
having the original instance updated.

My questions are:

1) Is there any way to achieve this using Twisted the way things are?

2) Is my copying-across-the-dict a good enough solution, and I should  
just forget about the whole thing?

3) I hear Zope 3 contains some kind of Twisted integration. For the  
life of me I can't find any information about this on the web, and I  
even bought a book on Zope 3 recently and the only reference to  
Twisted is that you can use Twisted Web instead of Zope's ZServer to  
service web requests.

4) I've been toying with Divmod Axiom, and I see there is Twisted  
Persisted (but can't find much info on it), plus there is Twisted  
Enterprise, but that is too close to relational databases for my  
liking. Do any of these projects have integration like this?

5) Does anyone else think this is a cool idea and like to see it  


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