[Twisted-Python] cleanup in twisted

[Joachim Boomberschloss]

--- Jp Calderone <exarkun at divmod.com> wrote:
> On Mon, 23 May 2005 02:40:53 -0700 (PDT), Joachim
> Boomberschloss <boomberschloss at yahoo.com> wrote:
> >
> >--- Bob Ippolito <bob at redivi.com> wrote:
> >>
> >> On May 22, 2005, at 8:46 AM, Joachim
> Boomberschloss
> >> wrote:
> >>
> >> > I just jotted down a little mechanism for
> >> cleaning-up
> >> > in Twisted, and I wanted to see if:
> >> > 1. other people think it's needed
> >> > 2. other people manage to use it
> >> >
> >> > What this does is enable one to define a
> >> __cleanup__
> >> > method which gets call either when the instance
> is
> >> > deleted, or when the reactor shuts down. It can
> >> return
> >> > a dereffed that delays the shutdown. The
> benefit
> >> is
> >> > being able to define communication-related
> stuff
> >> in
> >> > the cleanup method, which is not so useful to
> do
> >> in
> >> > __del__.
> >>
> >> This is just begging for object leaks, because
> >> __del__ disables
> >> aspects of cyclic GC.
> >
> >Hmmpf. What does this mean, and is there a simple
> way
> >of resolving it?
> >
> 
>   If you construct a reference cycle which contains
> an object which has a __del__ method, the entire
> cycle becomes "garbage" - Python cannot free any of
> the objects or call any of their __del__ methods. 
> Instead, it puts them into the gc module's `garbage'
> list and leaves them there forever.
> 
>   There's no simple way to resolve this (except to
> not implement __del__, of course ;).
> 
>   A non-simple way to resolve it is to use weakref
> callbacks instead of __del__.  Weakref callbacks
> have some nasty bugs in versions of Python older
> than 2.3.5 (more, the further back you go), and
> they're trickier to use than __del__.  They don't
> create garbage cycles, though.
> 

Can you point me to an example of this (preferably in
Twisted)? Is this whole cleanup thing worth my time
fixing it in your opinion?

Joe.


		
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