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...
> I'll admit, I didn't understand "Either that or it needs to not try to
> do a commit itself, and leave it up to the caller."
"The caller" in this case is the body of the context manager which
"calls" __exit__ by raising an exception or returning. I just meant
instead of:
for attempt in transaction.attempts(3):
with attempt as t:
.. do stuff, rely on context manager __exit__ to commit ..
You might change its contract to:
for attempt in transaction.attempts(3):
with attempt as t:
.. do stuff ..
t.commit() # you must commit yourself, __exit_ catches
# errors only and aborts on exception
But this would break existing code as well as probably going against the
spirit of intent.
- C
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