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I implemented a pre-commit hook on transaction supporting subscribers
within CPS for our indexation use case. (for ZODB-3.2.x on

if you're interested to take a look at it :


The difference I can see with your proposal is the abort() hook facility
that can be a good thing especially if the subscriber code has to
communicate with external programs for rollback purpose.


Jim Fulton wrote:
> I propose to add a pre-commit hook to ZODB.
> Problem
>   Sometimes, applications want to execute some code when
>   a transaction is committed.  For example, one might want to
>   delay object indexing until a transaction commits, rather
>   than indexing every time an object is changed. Or, someone
>   might want to check invariants only after a set of operations.
> Proposal
>   We add a new method to transaction objects:
>      def beforeCommitHook(hook, *args, **kw):
>          """Register a hook to call before the transaction is committed
>           The provided hook will be called after the transaction's
>           commit method has been called, but before the commit process
>           has been started.  The hook will be passed the given
>           positional and keyword arguments.
>           Multiple hooks can be registered and will be called in order.
>           This method can be called from executing hooks.  That is,
> executing
>           hooks can register more hooks.  (Applications should take care
>           to avoid creating infinite loops by recursvely registering
> hooks.)
>           Hooks are not called and are discarded if the transaction aborts.
>           """
>   We would also modify transaction commit methods to call hooks.  Hooks
> would
>   not be called on sub-transaction commit.  (If necessary, we could add
>   separate sub-transaction hooks, but I don't think we need this.)
>   This hook is very simple to use an implement and, I think, addresses
>   the requitement much more directly than implementing special data
>   managers.
> Thoughts?
> Anyone up for implementing this (with a doctest, of course)?
> I'd like to get this into ZODB 3.4.
> Jim

- --
Julien Anguenot | Nuxeo R&D (Paris, France)
CPS Plateform : http://www.cps-project.org
mail: anguenot at nuxeo.com; tel: +33 (0) 6 72 57 57 66
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