Hello, Can you check the condition inside the lock? The following pattern seems simpler to me:
def _populate(self): with self._lock: if self._populated: return # … populate … self._populated = True You can look at Apps.populate for an example of this pattern. Please forgive me if I missed a reason for using something more complicated. self._lock needs to be a RLock if _populate can call itself recursively in a given thread. Best regards, -- Aymeric. > On 12 Jul 2016, at 03:20, Cristiano Coelho <cristianocc...@gmail.com> wrote: > > Sorry for my above answer I think the actual locks should go like this, so > all threads can actually go to the wait line while _populating is True. > > def _populate(self): > > self.lock.acquire() > > if self._populating: > self.lock.wait() > self.lock.release() > return > > self._populating = True > > self.lock.release() > > ... > > self.lock.acquire() > self._populating = False > self.lock.notify_all() > self.lock.release() > > > > El lunes, 11 de julio de 2016, 22:14:04 (UTC-3), Cristiano Coelho escribió: > Wouldn't a standard Lock do the trick? Also you are still vulnerable to a > race condition when reading self._populating, if the goal is to avoid > populating the object more than once in a short interval (in a case where > multiple requests hit the server before the object is initialized for the > first time?) you are still running all the critical code on all threads if > they check self.populating before it is set to True. > > Would a condition work better in this case? Something like this.. (add any > missing try/finally/with that might be required), warning, NOT TESTED, just > an idea. > The below code will not be prone to race conditions as the variables are > always read/set under a lock, and also the critical section code will be only > executed ONCE even if multiple threads attempt to run it at once, while still > locking all threads to prevent returning before the code is done. > > def __init__(self, regex, urlconf_name, default_kwargs=None, app_name=None, > namespace=None): > > ... > > self._populating = False > self.lock = threading.Condition() > > def _populate(self): > > self.lock.acquire() > > if self._populating: > self.lock.wait() > self.lock.release() > return > > self._populating = True > > ... > > self._populating = False > self.lock.notify_all() > self.lock.release() > > > > > > El lunes, 11 de julio de 2016, 10:08:50 (UTC-3), a.br...@rataran.com <> > escribió: > Hello everyone. > > As suggested by Markus on django-users group, I'm posting this here too. > > ------- > > I'm using django (1, 10, 0, u'beta', 1). > > When I try to reverse url in shell everything goes fine. > > When under nginx/uwsgi with many concurrent request I get > > ... /local/lib/python2.7/site-packages/django/urls/resolvers.py", line 241, > in reverse_dict > return self._reverse_dict[language_code] > KeyError: 'it' > > After a wile I figured out that RegexURLResolver is memoized by get_resolver > and so it acts like a singleton for a certain number of requests. > > Analyzing the code of RegexURLResolver I found that the method _poupulate > will return directly if it has been called before and not yet finished. > > ... > def _populate(self): > if self._populating: > return > self._populating = True > ... > > if used for recursive call in a single thread this will not hurt, but in my > case in uwsgi multi thread mode I got the error. > > here is my quick and dirty fix: > > class RegexURLResolver(LocaleRegexProvider): > def __init__(self, regex, urlconf_name, default_kwargs=None, > app_name=None, namespace=None): > > ... > > self._populating = False > self.RLock = threading.RLock() > > ... > > def _populate(self): > if self._populating: > self.RLock.acquire() > self.RLock.release() > return > self._populating = True > self.RLock.acquire() > > ... > > self._populating = False > self.RLock.release() > > > Does anyone know if there is a better solution? > > Thank you. > > -- > You received this message because you are subscribed to the Google Groups > "Django developers (Contributions to Django itself)" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to django-developers+unsubscr...@googlegroups.com > <mailto:django-developers+unsubscr...@googlegroups.com>. > To post to this group, send email to django-developers@googlegroups.com > <mailto:django-developers@googlegroups.com>. > Visit this group at https://groups.google.com/group/django-developers > <https://groups.google.com/group/django-developers>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/django-developers/922ca727-dd60-41dd-9b78-b8d8fe9ebd16%40googlegroups.com > > <https://groups.google.com/d/msgid/django-developers/922ca727-dd60-41dd-9b78-b8d8fe9ebd16%40googlegroups.com?utm_medium=email&utm_source=footer>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. -- You received this message because you are subscribed to the Google Groups "Django developers (Contributions to Django itself)" group. 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