Why do things get started twice in django sometimes? I see the framework
being started twice here. Also if you overload the __init__(self): of
models, that too gets called twice. I've never understood this, but the
singleton pattern seems to provide a nice workaround.
Brian
On Mon, Dec 13, 2010 at 5:19 PM, Mike Dewhirst <mi...@dewhirst.com.au>wrote:
> On Dec 13, 10:57 am, martvefun <martve...@gmail.com> wrote:
> > On 10-12-10 11:09, Mike Dewhirst wrote:
> > > On 10/12/2010 7:43pm, martvefun wrote:
> > >> On 09-12-10 01:37, Mike Dewhirst wrote:
> > >>> It seems like a good place to put it. Maybe you can test to see if
> the
> > >>> threads have been started already?
>
> <snip>
>
> > Thank you, it works if I have to call in the same files (like s1 =
> > singleton() ; s2 = singleton() ) but here I still have two calls
> >
> > class singleton(object):
> > """ designed by Oren Tirosh and Jeff Pitman """
> > def __new__(self, *args, **kwargs):
> > print "call singleton"
> > if not '_singleton' in self.__dict__:
> > print "first time created"
> > slate = object.__new__(self)
> > slate.state = {
> > 'threads':True,
> > # add other state things as required
> > }
> > self._singleton = slate
> > return self._singleton
> >
> > singleton()
> > print "Server is now runing"
> >
> > gives me :
> > $ python manage.py runserver
> > call singleton
> > first time created
> > Server is now runing
> > call singleton
> > first time created
> > Server is now runing
> > Validating models...
> > 0 errors found
>
> I just tested it myself and while it definitely works - meaning it
> does return exactly the same object each time - manage.py runserver
> apparently starts the framework twice. Hence you see it twice. I
> noticed that when you edit a file and the dev server automatically
> restarts, the singleton gets recreated but only once as expected.
>
> Here is some research by Graham Dumpleton earlier this year and which
> explains the process in detail ...
>
> http://blog.dscpl.com.au/2010/03/improved-wsgi-script-for-use-with.html
>
> If you decide to use a singleton to monitor state you might have to
> look for somewhere safe to start it.
>
> >
> > And anyway I just realised another problem : I'll need to have access to
> > the objects I created from views.
>
> I think it would work from anywhere you can call the code but you need
> to test it.
>
> Mike
>
> > The idea is to send a message to the thread when a certain action is
> > done (like user registration, validate choices...) but to do that I need
> > an access to this object (I cannot create another one because of
> > concurrency safety)
> >
> > Any idea ?
>
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--
Brian Bouterse
ITng Services
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