On Sat, 2012-03-31 at 07:49 -0400, Jim Fulton wrote:
> On Thu, Mar 29, 2012 at 6:59 PM, Chris McDonough <chr...@plope.com> wrote:
> > On Thu, 2012-03-29 at 07:18 -0400, Jim Fulton wrote:
> >> On Wed, Mar 28, 2012 at 6:37 PM, Chris McDonough <chr...@plope.com> wrote:
> >> > On Wed, 2012-03-28 at 17:06 -0400, Jim Fulton wrote:
> >> >> On Wed, Mar 28, 2012 at 4:37 PM, Chris McDonough <chr...@plope.com>
> >> >> wrote:
> >> >> > On Wed, 2012-03-28 at 14:21 -0400, Jim Fulton wrote:
> >> >> ...
> >> >> > A decorator for running some code in the context of a txn and retrying
> >> >> > retryable exceptions would be nice higher level behavior. Â I'd be
> >> >> > willing to do this work over this weekend.
> >> >>
> >> >> Cool. Don't forget the transaction note part. :)
> >> >> Too many transactions in our apps don't have
> >> >> notes, especially transactions that happen
> >> >> outside of web requests.
> >> >>
> >> >> > In the meantime, I think the existing attempts context manager still
> >> >> > needs the small fix I proposed in my original message. Â Can you
> >> >> > confirm
> >> >> > that my understanding of the its intent seems roughly correct?
> >> >>
> >> >> I didn't see a statement of intent. I think your fix us good,
> >> >> but the code (that I wrote and your fix) makes my head hurt. :)
> >> >>
> >> >> I'd say, make some test cases for the bug and make it pass.
> >> >
> >> > OK. Once I fix this "Attempts" bug, I think the decorator code is just
> >> > a higher level interface that uses it:
> >> >
> >> > class job(object):
> >> > def __init__(self, attempts=1, note=None, manager=None):
> >> > self.attempts = attempts
> >> > self.note = note
> >> > if manager is None:
> >> > manager = transaction.manager
> >> > self.manager = manager
> >> >
> >> > def __call__(self, wrapped):
> >> > note = self.note
> >> > if note is None:
> >> > note = getattr(wrapped, '__name__', None)
> >> > def inner(*arg, **kw):
> >> > for attempt in self.manager.attempts(self.attempts):
> >> > with attempt as t:
> >> > t.note(note)
> >> > return wrapped(*arg, **kw)
> >> >
> >> > .. or something like that...
> >>
> >> It could be written that way, although I would
> >> use a much simpler implementation.
> >>
> >> The attempt design was a reach to overcome
> >> the limitations of the with statement. I'm not at all happy
> >> with it, although I couldn't think of anything better at the
> >> time. I hate to build on it.
> >
> > It's brainbusting, yes, but it works. Do you have any other specific
> > pattern in mind?
>
>
> def job(func=None, retries=3):
> if func is None:
> return lambda f: job(f, retries)
>
> note = func.__doc__
> if note:
> note = note.split('\n', 1)[0]
> else:
> note = func.__name__
>
> for i in xrange(retries + 1):
> t = manager.begin()
> if i:
> t.note("%s (retry: %s)" % (note, i))
> else:
> t.note(note)
>
> try:
> func(t)
> t.commit()
> except TransientError:
> t.abort()
> else:
> break
>
> The above is untested, but you get the idea.
>
> Aside from note and decorator support,
> this is straightforward. It encapsulates
> standard boilerplate.
Alright, I took a stab at it with tests, albeit as a method of the
TransactionManager class (and an alias in __init__ as "job"):
https://mail.zope.org/pipermail/checkins/2012-April/059120.html
- C
_______________________________________________
For more information about ZODB, see http://zodb.org/
ZODB-Dev mailing list - ZODB-Dev@zope.org
https://mail.zope.org/mailman/listinfo/zodb-dev
