[Zope-dev] Refresh trashes acquisition

[Ross Boylan]

On Wed, Jul 24, 2002 at 10:38:44AM -0400, Matthew T. Kromer wrote:
> Ross Boylan wrote:
> 
> >I find that when I refresh my product it destroys some of the
> >containment relationships.  Things start failing, and as far as I can
> >tell the only recovery is to completely rebuild the object.
> >
> >This is a big problem, and if anyone could explain what is going on
> >and how to avoid it I would appreciate it.
> >
> >Here is the result of aq_chain before the refresh:
> >[<RankQuestion instance at 8dd5620>,
> ><OriginalSuborder instance at 8c9f8d8>, <EMailBallot instance at
> >8dfc870>, <__FactoryDispatcher__ instance at 8e73770>,
> ><ProductDispatcher instance at 83f0618>, <Folder instance at 8d5733
> >
> >and after
> >[<RankQuestion instance at 8dee2d0>]
> > 
> >
> [...]
> 
> > 
> >
> 
> Hmm, while what you're referring to is "refresh" in the sense of a 
> product reload, it's important to first state that *no* acquisition is 
> expected to survive between transactions.
> 
> Each transaction must separately acquire its objects; if you try to pass 
> wrapped objects between transactions or threads you're going to end up 
> in trouble.
> 
> Secondly, when a product is refreshed, the extensionclass module will 
> probably create new base classes for any ExtensionClass derived class 
> file.  I dont *think* you can get much mileage out of knowing the id 
> (address) of a class now, but be aware that a refresh will likely cause 
> that address to change.  I have seen some bizarre errors where module 
> "constants" changed because of a reload, and "is" tests broke because 
> "is" tests the object address.
> 
> None of this is explicitly what you're asking about -- but I think what 
> you're trying to do is in violation of the "no wrapped objects should be 
> stored past a transaction boundary" rule.
> 
> However, I may be misreading your question too -- which is why I mention 
> those two rules above so YOU can see if they make sense in your context.
> 

The first point is definitely relevant, and explains why I am having
problems.  It's surprising what I'm doing is workign at all!  The
class redefinition in the second point might explain some of the
timing of the problems, but it's the instances, not the classes that I
am interested in.

The acquisition I want to do is in the object containment hierarchy,
but URL of the request will also have this hieararchy.  Is
there some way I can grab it at the appropriate time?

Your comments also clarify a point that was unclear to me from the
documentation on acquisition.  The documents refers to the object
containment hierarchy and the request path hierarchy, and recommend
keeping them consistent.  But I didn't understand which hierarchy it
used if they weren't.  Apparently only the request path matters.

It may be helpful to say more about the exact relations in my case:
[indentation indicates containment in this diagram; capital letters
are for objects]
B  ballot
  Q1  question
   R1a response
   R1b response
   SR  suborder of responses
      see below for suborders
     R1a
     R1b (same objects as the R1's above)
  Q2  question ...
  NQ  "namestyle" of questions (determines labeling)
  NR  namestyle of responses
  SQ  suborder of questions (sequential, random, ...)
   this suborder contains a list of the same questions Q1, Q2, etc
   that the ballot B holds.
   It also the name of the namestyle, to be acquired from the container.
Generally, B and maybe Q will be in my request path, and the other
items are not.

I ask the suborders for list of items, so they give me back a list of
Q's or R's.  The items in those lists were the ones I was trying to
wrap.

At the most extreme case, I get a response R from the suborder list of
a question Q, and I get the Q from the suborder of the ballot.  So I't
two levels removed from my original context, the ballot B, that has
the namestyle I'm trying to acquire.  The suborder on the Question
needs to acquire the namestyle from the Ballot.

Finally, I may be making an overly conservative assumption about
ObjectManagers.  Without it, the suborders would not need to hold onto
object references.  It's easiest to explain this with a specific
example.  I want to be able to recover the original order questions
were entered into the ballot.  Ballot is a subclass of ObjectManager.
I believe I am not allowed to make any assumptions about the order
its items will be returned by objectItems(), so I am using the
suborder to track that.

P.S. I also assume that objectItems('type') gets only objects of that
type, not subtypes.  Does anyone know if that's so?