[Twisted-Python] Twisted.Persisted ~ ZODB

Kevin Koym kevin at praxsys.com
Fri Jul 2 09:05:02 EDT 2004


Matt,
I have not integrated the two yet.... (so perhaps my other message was 
not appropriate for the list... but I did want to mention the modeling 
package as being another direction to look for object persistance.) I am 
interested in hearing what others have to say about modeling and twisted 
too.  I can tell, based on the activity on modeling list, things are 
moving on it quicker than was before. I believe that the community 
around modeling is starting to grow... so it might have further 
usefulness/robustness in the future than it might have in the past.

Thanks,
Kevin

Matt Goodall wrote:

>On Thu, 2004-07-01 at 18:07 -0500, Kevin wrote:
>  
>
>>you might also look at http://modeling.sourceforge.net/
>>
>>it is definitely different than other persistance layers in python- but 
>>if you have a background similar to mine, it will feel more comfortable 
>>to some of these other systems.
>>    
>>
>
>I haven't looked at Modeling for a long time. IIRC, it manages database
>connections using its own pool and all interaction takes place within an
>EditingContext. Out of interest, how do you integrate Twisted and
>Modeling? Do you just defer the calls into Modeling to a thread or do
>you have something clever going on?
>
>Thanks, Matt
>
>  
>
>>good luck,
>>kevin
>>
>>Jp Calderone wrote:
>>
>>    
>>
>>>Eugene Coetzee wrote:
>>>
>>>      
>>>
>>>>Hi,
>>>>
>>>>Being new to both Twisted and ZODB and not finding too much info on 
>>>>Twisted.Persisted by googling I have decided to post this question.
>>>>
>>>>I have also noticed a few projects running Twisted "on top of"  ZODB 
>>>>as it were.
>>>>
>>>>I get the impression that Twisted.Persisted is more of an utility 
>>>>add-on  to Twisted whereas ZODB is a full fledged object database.
>>>>        
>>>>
>>>  That is true.  Nothing in twisted.persisted is usable by itself as a 
>>>persistence mechanism for a non-trivial application.
>>>
>>>  AOT and Marmalade are graph serialization formats.  Neither supports 
>>>new-style objects very well, IIRC.  Even if they do, neither is 
>>>particularly quick, nor provides anything beyond simple storage of a 
>>>complete object graph, hardly the only requirement for a database.
>>>
>>>  dirdbm is a cute toy, but not again really useful as a non-trivial 
>>>data store.  It's slow and fragile, and doesn't provide any 
>>>functionality beyond what the bsddb module in Python 2.3 provides.
>>>
>>>  sob is a handy front-end to AOT, Marmalade, pickle, and tac files.
>>>
>>>  crefutil is helper code for aot and jelly and perhaps some other 
>>>serialization modules.
>>>
>>>  The styles module has all the cool code.  It lets you pickle 
>>>otherwise unpickleable types and provides the Versioned class, which 
>>>lets you deal with mixing old data with new code.
>>>
>>>      
>>>
>>>>Still - I  would very much like to  use Twisted.Persisted for 
>>>>trancient data/metadata in a new project I'm tackling cause it is 
>>>>always good to minimize dependencies and I know I can use postgreSQL 
>>>>with Twisted for heavy duty stuff - which I still believe a better 
>>>>option than OODB.
>>>>        
>>>>
>>>  Unless you have very little data, and you don't care _terribly_ if 
>>>you lose it, twisted.persisted probably isn't going to do it for you.
>>>
>>>      
>>>
>>>>How does Twisted.Persisted  compare to ZODB - if such a comparison 
>>>>can be made? Any other OODB's to be considered for use with Twisted?
>>>>        
>>>>
>>>  You might look at Atop.  It's somewhat lighter weight than ZODB. 
>>>http://www.divmod.org/ has some docs, but it needs more.  It also 
>>>isn't distributed separately from Quotient yet (but is easily 
>>>separable once you download it).
>>>
>>>      
>>>
>>>>I would also very much appreciate some links to on-line docs/examples 
>>>>regarding Twisted.Persisted if they exist.
>>>>kind regards,
>>>>
>>>>        
>>>>
>>>  I wish I could point you at something, but I hope the above has been 
>>>an adequate substitute.
>>>
>>>  Jp
>>>
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>>>
>>>      
>>>
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>>    
>>

-- 
Kevin Koym

Innovation

kevin at praxsys.com
+1.512.698.9328 cell in US


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