Nice, Massimo will there be a new book?
On 4 aug, 09:04, mdipierro <mdipie...@cs.depaul.edu> wrote:
> Changing now into utcnow would break backward compatibility.
>
> I do agree with you that othen people may want to use
>
> Field(....,default=datetime.utcnow())
>
> instead of
>
> Field(....,default=request.now)
>
> I will add a comment about this in the book.
>
> Massimo
>
> On Aug 3, 3:22 am, Armin Ronacher <armin.ronac...@active-4.com> wrote:
>
> > Hi,
>
> > > True. but I would not call it a race condition. We timestamp
> > > everything with the time when a request arrives, not when it is
> > > processed, unless specified otherwise (datetime.now() instead of
> > > request.now)
>
> > True. But that does not make it a better idea. Also, datetime.now()
> > should be consistently replaced with datetime.utcnow() because using
> > anythign else than UTC data internally is problematic for various
> > reasons. See the discussion on that topic in various i18n/l10n
> > libraries such as babel / pytz.
>
> > > True but I believe we never do that in web2py. It is also true that
> > > nothing prevent the user from doing it but the same would be true with
> > > other frameworks.
>
> > You're not doing it, a user might be doing that by accident or because
> > he things it should work. This problem does not exist in other
> > frameworks because besides web2py I don't know a single one that does
> > this sort of execfile() + namespace thing or uses any other kind of
> > throwaway modules. As soon as a single reference leaks from the
> > execfile()'d namespace you're in big troubles and due to the open
> > nature of Python this could happen very, very fast.
>
> > > Yes but because all relevant application code is executed within a
> > > context and there are no references outside the context to stuff
> > > inside the context, when a request is completed, the context is
> > > deleted and everything should be garbage collected.
>
> > That depends on two things. First not having a reference leaked,
> > which could happen with abstract base classes and other stuff that
> > uses registries or steals non-weak references. Also and more
> > importantly, the file descriptor limit is very low and the majority of
> > Python implementations will only collect that on the GC run (always,
> > no matter where references are). Say you're opening three files per
> > request and you have more than 100 requests/sec you could lose all
> > file descriptors that are available before the GC even thought about
> > running.
>
> > Regards,
> > Armin
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