[Zope-dev] Re: post publishing hook

[Florent Guillaume]

Dieter Maurer  <dieter at handshake.de> wrote:
> Christian Heimes wrote at 2005-4-1 22:28 +0200:
> > ...
> >You want to bind some actions to the transaction system because you want 
> >to execute some code at the end of the first phase of the 2 phase 
> >commit.
> 
> I do not think that Florent wants to execute things at the end
> or in the first commit phase. Instead, he wants to execute something
> *BEFORE* this phase.

Yes, wherever it's inserted, I want to do additional processing before
everything is finalized, and in some cases I want to be able to abort
the transaction, and to create and change objects in the ZODB.

> >Hooking into the transaction machinery of ZODB is very easy. Write 
> >your own DateManager implementing the IDateManager interface and 
> >register it into the current transaction using get_transaction.register(DM).
> >
> >For your use case overwrite the tpc_vote() method of the data manager to 
> >do the indexing at the boundary between the two phases.
> 
> This will not work for Florent's use case,
> at least not in the current ZODB (for Zope 2.7).
> 
> Reason:
> 
>   The transaction freezes the set of objects it processes
>   in the commit *BEFORE* the first commit phase.
> 
>   Therefore, no "tpc_vote" is allowed to modify any persistent
>   object. Failure to do so leads to extremely nasty
>   persistency errors (the object is marked changed but
>   no transaction knows about it -- no change to this object in the future
>   will get persisted until a restart).

Ah, that was what I was afraid of, but I was assured it was not the
case. I'll have to reread that transaction code... and maybe readd the
low-tech post-publishing hook I was thinking of.

Thanks Dieter,

Florent

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