[Pymilter] no memory release when assigning chunks to self.fp in milter-template.py

[Stuart D. Gathman]

On Tue, 4 Feb 2020, joao reis wrote:

> With "del self.fp" it is consuming 244.6 MiB in just one hour.

That proves pretty conclusively that the problem is not with postfix or
pymilter.  Either BytesIO/StringIO are badly broken (unlikely, we can
make a non-milter test), or you have "leaked" a reference to self.fp
(or self.fp.getvalue()) somewhere where it is being colllected globally.

Although, you are doing it wrong:

>       if self.fp:
>       self.fp.close()
>       self.fp = None
>       del self.fp
>       return Milter.CONTINUE

You need to delete *before* setting to None, otherwise it is a noop.
But even just setting it to None will immediately reclaim the memory
in C-Python when it is the last reference.  So apparently, it
is not the last reference.

-- 
 	      Stuart D. Gathman <stuart at gathman.org>
"Confutatis maledictis, flammis acribus addictis" - background song for
a Microsoft sponsored "Where do you want to go from here?" commercial.