Main loop of the ConCache, starts updates in intervals and
        answers requests from the MWorkers

def run(self):
        '''
        Main loop of the ConCache, starts updates in intervals and
        answers requests from the MWorkers
        '''
        context = zmq.Context()
        # the socket for incoming cache requests
        creq_in = context.socket(zmq.REP)
        creq_in.setsockopt(zmq.LINGER, 100)
        creq_in.bind('ipc://' + self.cache_sock)

        # the socket for incoming cache-updates from workers
        cupd_in = context.socket(zmq.SUB)
        cupd_in.setsockopt(zmq.SUBSCRIBE, b'')
        cupd_in.setsockopt(zmq.LINGER, 100)
        cupd_in.bind('ipc://' + self.update_sock)

        # the socket for the timer-event
        timer_in = context.socket(zmq.SUB)
        timer_in.setsockopt(zmq.SUBSCRIBE, b'')
        timer_in.setsockopt(zmq.LINGER, 100)
        timer_in.connect('ipc://' + self.upd_t_sock)

        poller = zmq.Poller()
        poller.register(creq_in, zmq.POLLIN)
        poller.register(cupd_in, zmq.POLLIN)
        poller.register(timer_in, zmq.POLLIN)

        # our serializer
        serial = salt.payload.Serial(self.opts.get('serial', ''))

        # register a signal handler
        signal.signal(signal.SIGINT, self.signal_handler)

        # secure the sockets from the world
        self.secure()

        log.info('ConCache started')

        while self.running:

            # we check for new events with the poller
            try:
                socks = dict(poller.poll(1))
            except KeyboardInterrupt:
                self.stop()
            except zmq.ZMQError as zmq_err:
                log.error('ConCache ZeroMQ-Error occurred')
                log.exception(zmq_err)
                self.stop()

            # check for next cache-request
            if socks.get(creq_in) == zmq.POLLIN:
                msg = serial.loads(creq_in.recv())
                log.debug('ConCache Received request: %s', msg)

                # requests to the minion list are send as str's
                if isinstance(msg, six.string_types):
                    if msg == 'minions':
                        # Send reply back to client
                        reply = serial.dumps(self.minions)
                        creq_in.send(reply)

            # check for next cache-update from workers
            if socks.get(cupd_in) == zmq.POLLIN:
                new_c_data = serial.loads(cupd_in.recv())
                # tell the worker to exit
                #cupd_in.send(serial.dumps('ACK'))

                # check if the returned data is usable
                if not isinstance(new_c_data, list):
                    log.error('ConCache Worker returned unusable result')
                    del new_c_data
                    continue

                # the cache will receive lists of minions
                # 1. if the list only has 1 item, its from an MWorker, we append it
                # 2. if the list contains another list, its from a CacheWorker and
                #    the currently cached minions are replaced with that list
                # 3. anything else is considered malformed

                try:

                    if not new_c_data:
                        log.debug('ConCache Got empty update from worker')
                        continue

                    data = new_c_data[0]

                    if isinstance(data, six.string_types):
                        if data not in self.minions:
                            log.debug('ConCache Adding minion %s to cache',
                                      new_c_data[0])
                            self.minions.append(data)

                    elif isinstance(data, list):
                        log.debug('ConCache Replacing minion list from worker')
                        self.minions = data

                except IndexError:
                    log.debug('ConCache Got malformed result dict from worker')
                    del new_c_data

                log.info('ConCache %s entries in cache', len(self.minions))

            # check for next timer-event to start new jobs
            if socks.get(timer_in) == zmq.POLLIN:
                sec_event = serial.loads(timer_in.recv())

                # update the list every 30 seconds
                if int(sec_event % 30) == 0:
                    cw = CacheWorker(self.opts)
                    cw.start()

        self.stop()
        creq_in.close()
        cupd_in.close()
        timer_in.close()
        context.term()
        log.debug('ConCache Shutting down')