[Zope-dev] How to develope a ZObject to connect to an socket server?

[Leonardo Rochael Almeida]

On Thu, 2002-08-22 at 10:47, Casey Duncan wrote:
> On Thursday 22 August 2002 09:04 am, Juan Carlos CORU=D1A wrote:
> > Hi all!
> >=20
> > I'm trying to develope a zope object that connects to a external socket
> > server in order to comun=EDcate with it and receive some events (Maybe =
I
> > need a thread to process events).
>=20
> That's probably a good idea if not necessary if Zope must respond to inco=
ming=20
> events other than over HTTP.
> =20
> > The problem is how to establish the connection at the start of zope and
> > to disconnect at the end. After some test assigning the socket server
> > object to _v_ variables in the zope object, it missed the connection
> > after a while. It seems that it can't maintain the reference stored in
> > the _v_ variable.
>=20
> I would recommend using module level global variables instead.

And you can initialize them on the module body, which means it will run
only one time, either at Zope init or at the first time the module is
imported.

Disconnecting at the end could be a problem though. I don't know of a
reliable way to know when Zope is going to shut down because it could be
stopped from the command line (./stop) where the Zope process will just
be killed. Maybe you can plug into the new Zope signal handling stuff.

> Volatile vars=20
> are just that. If a persistent object with volatiles gets unloaded by the=
=20
> ZODB (which can happen at any time arbitrarily), its volatiles go bye bye=
.=20
>=20
> Volatiles are also thread specific.

Which means that, with Zope's default 4 (I think) worker threads, you
can get as much as 4 simultaneous open connections (Yes, most database
adapters do that on purpose).

> Module globals are shared across threads,=20
> which may be a good or bad thing depending on your situation ;^).

But at least they're unique within Zope.

> =20
> > I thing that the behaviour is something like database connections and
> > I'm looking into some database connection objects to find out the
> > mechanism used.
>=20
> Yup. Except they don't receive events except in response to a request com=
ing=20
> from Zope.


Cheers, Leo

--=20
Ideas don't stay in some minds very long because they don't like
solitary confinement.