[Pymilter] Dataproxy proxy in pymilter

[Stuart D Gathman]

On May 13, Abhijeet Rastogi transmitted in part:

> Before wanting to have my answer, I need to understand how a milter
> works. So, it it like when a new mail is in queue, one instance of
> milter script is spawned for each mail?

No.  One instance of a user class derived from Milter.Base is created
for each SMTP connection to the MTA.  Each connection also has its 
own Thread.

> I need to have a functionality like having a python object common to
> all milter instances. The reason I want to do this is because I need a
> persistent database connection to postgres to do some queries and
> fetch data.

So create a global object.  Caveat: since each SMTP connection is its own
thread, you need to wrap non-reentrant global objects with something
like:

import thread

my_lock = thread.allocate_lock()

my_global = MakeMyGlobalObject()

class MyMilter(Milter.Base):

   # callback picked at random
   def hello(name):
     my_lock.acquire()
     my_global.frobigate(name)
     my_lock.release()
   ...


Another approach is to use the multiprocessing or threading module as
illustrated in the example milter:

http://pythonhosted.org/pymilter/milter-template_8py-example.html