import traceback
from twisted.internet.task import LoopingCall

class Manager:

    def __init__(self):
        self._job2loop = {}

    def register(self, *tasks):
        for task in tasks:
            self._job2loop[task.name] = LoopingCall(self.run_job, task)

    def start(self, *schedule):
        for task, timer in schedule:
            if task.name in self._job2loop:
                self._job2loop[task.name].start(timer, False)
                print 'Job %s started' % task.name
            else:
                print 'Job not scheduled: %s' % task.name

    def run_job(self, task):
        job = task.job()
        try:
            job()
        except Exception, e:
            self.exception_handler(task, e)
        else:
            if task.job_done():
                self.finalize(task)

    def exception_handler(self, task, e):
        print 'Exception happened in %s.%s' % (task.name, task.job().__name__)
        print e
        print traceback.format_exc()
        self.finalize(task)

    def finalize(self, task):
        self._job2loop[task.name].stop()
        del self._job2loop[task.name]
        print '%s finalized' % task.name
        if not self._job2loop:
            reactor.stop()

class Countdown(object):

    def __init__(self, name, start):
        self.name = name
        self.counter = start

    def job_done(self):
        if not self.counter:
            return True
        return False

    def job(self):
        return self.count

    def count(self):
        if self.counter <= 0:
            raise ValueError, '%s.counter = %d, value must be greater than 0' % (self.name, self.counter)
        print 'counter %s:' % str(self.name), self.counter, '...'
        self.counter -= 1

cntA = Countdown('AAA', 5)
cntB = Countdown('BB', 10)
cntC = Countdown('C', 7)
cntErr = Countdown('Err', 0)

mng = Manager()

mng.register(cntA, cntB, cntC, cntErr)

mng.start((cntA, 1), (cntB, 0.3))
mng.start((cntC, 0.5), (cntErr, 1))

from twisted.internet import reactor
reactor.run()