import time
from twisted.application import service, internet
from twisted.internet import defer, task, reactor

def sleep(t):
    return task.deferLater(reactor, t, lambda: None)

class WorkerApp(service.Service):
    myd = None
    def __init__(self):
        print("workerapp init")

    async def _startService(self):
        self.running = True
        while self.running:
            self.myd = defer.Deferred()
            print("1")
            await sleep(2)
            print("2")
            await sleep(2)
            raise Exception('my error')
            print("3")
            await sleep(2)
            self.myd.callback(self)

    def startService(self):
        defer.ensureDeferred(self._startService())

    def stopService(self):
        print("stop service")
        self.myd.addCallback(setattr, "running", False)
        return self.myd

application = service.Application("my twisted app")
service = WorkerApp()
service.setServiceParent(application)