[Twisted-Python] reactor.addSystemEventTrigger("before", "shutdown", self.logout)

[Manlio Perillo]

Jean-Paul Calderone ha scritto:
> On Fri, 14 Apr 2006 17:15:25 -0200, Manlio Perillo
> <manlio_perillo at libero.it> wrote:
>> Hi.
>>
>> I would like to have a function be called at the very end of the reactor
>> lifetime.
>>
>> I have tried with the statement in the subject, where self.logout sends
>> a packet via UDP (self is an instance of a class derived from
>> DatagramProtocol).
>>
> 
> Services or the underlying APIs they rely on (addSystemEventTrigger) are
> the correct way to go about this.
> 

Ok.

>> But this seems to be not allowed.
>> I obtain:
>>
> [...]
>>
>> This means, in short, that in a shutdown event I can't use the reactor?
>> I think that this should be documented.
>>
> 
> You can, and many applications do.  Perhaps you have found a bug, or
> perhaps you are using system event triggers improperly. Could you post
> a minimal, complete example which will reproduce this behavior?
> 

Sure!
My system is Windows XP SP2, Python 2.4.3, Twisted 2.2.0


##########
import sys

from twisted.python import log

from twisted.internet.protocol import DatagramProtocol
from twisted.internet import defer, reactor


class Server(DatagramProtocol):
    def datagramReceived(self, data, addr):
        print "server: received from %s:%d" % addr, data
        self.transport.write("LOGGED OUT", addr)


class Client(DatagramProtocol):
    def __init__(self):
        self.deferred = defer.Deferred()

    def startProtocol(self):
        self.transport.connect("127.0.0.1", 9000)

        reactor.addSystemEventTrigger("before", "shutdown", self.logout)

    def connectionRefused(self):
        print "unable to connect"

    def datagramReceived(self, data, addr):
        print "client: received from %s:%d" % addr, data
        self.deferred.callback(data)

    def logout(self):
        self.transport.write("LOGOUT")

        return self.deferred



reactor.listenUDP(9000, Server())
reactor.listenUDP(0, Client())

reactor.callLater(2, reactor.stop)

log.startLogging(sys.stdout)
reactor.run()

#############



The problem seems to be with the response.
There are no problems if logout does not return a deferred (but in this
case the client does not sees the LOGGED OUT response).


Is this an improper use of system event triggers?



Thanks and regards  Manlio Perillo