twisted - interrupt callback via KeyboardInterrupt

Question

I'm currently repeating a task in a for loop inside a callback using Twisted, but would like the reactor to break the loop in the callback (one) if the user issues a KeyboardInterrupt via Ctrl-C. From what I have tested, the reactor only stops or processes interrupts at the end of the callback.

Is there any way of sending a KeyboardInterrupt to the callback or the error handler in the middle of the callback run?

Cheers,

Chris

#!/usr/bin/env python

from twisted.internet import reactor, defer


def one(result):
    print "Start one()"
    for i in xrange(10000):
        print i
    print "End one()"
    reactor.stop()


def oneErrorHandler(failure):
    print failure
    print "INTERRUPTING one()"
    reactor.stop()    


if __name__ == '__main__':

    d = defer.Deferred()
    d.addCallback(one)
    d.addErrback(oneErrorHandler)
    reactor.callLater(1, d.callback, 'result')

    print "STARTING REACTOR..."
    try:
        reactor.run()
    except KeyboardInterrupt:
        print "Interrupted by keyboard. Exiting."
        reactor.stop()

Answer 1

I got this working dandy. The fired SIGINT sets a flag running for any running task in my code, and additionally calls reactor.callFromThread(reactor.stop) to stop any twisted running code:

#!/usr/bin/env python

import sys
import twisted
import re
from twisted.internet import reactor, defer, task
import signal


def one(result, token):
    print "Start one()"
    for i in xrange(1000):
        print i
        if token.running is False:
            raise KeyboardInterrupt()
            #reactor.callFromThread(reactor.stop) # this doesn't work
    print "End one()"

def oneErrorHandler(failure):
    print "INTERRUPTING one(): Unkown Exception"
    import traceback
    print traceback.format_exc()
    reactor.stop()

def oneKeyboardInterruptHandler(failure):
    failure.trap(KeyboardInterrupt)
    print "INTERRUPTING one(): KeyboardInterrupt"
    reactor.stop()

def repeatingTask(token):
    d = defer.Deferred()
    d.addCallback(one, token)
    d.addErrback(oneKeyboardInterruptHandler)
    d.addErrback(oneErrorHandler)
    d.callback('result')

class Token(object):
    def __init__(self):
        self.running = True

def sayBye():
    print "bye bye."


if __name__ == '__main__':

    token = Token()

    def customHandler(signum, stackframe):
        print "Got signal: %s" % signum
        token.running = False                # to stop my code
        reactor.callFromThread(reactor.stop) # to stop twisted code when in the reactor loop
    signal.signal(signal.SIGINT, customHandler)

    t2 = task.LoopingCall(reactor.callLater, 0, repeatingTask, token)
    t2.start(5) 

    reactor.addSystemEventTrigger('during', 'shutdown', sayBye)

    print "STARTING REACTOR..."
    reactor.run()