platypush/platypush/bus/__init__.py

import logging
import threading
import time

from queue import Queue

from platypush.config import Config
from platypush.message.event import Event, StopEvent

logger = logging.getLogger(__name__)


class Bus(object):
    """ Main local bus where the daemon will listen for new messages """

    _MSG_EXPIRY_TIMEOUT = 60.0  # Consider a message on the bus as expired
                                # after one minute without being picked up

    def __init__(self, on_message=None):
        self.bus = Queue()
        self.on_message = on_message
        self.thread_id = threading.get_ident()

    def post(self, msg):
        """ Sends a message to the bus """
        self.bus.put(msg)

    def get(self):
        """ Reads one message from the bus """
        return self.bus.get()

    def stop(self):
        """ Stops the bus by sending a STOP event """
        evt = StopEvent(target=Config.get('device_id'),
                        origin=Config.get('device_id'),
                        thread_id=self.thread_id)

        self.post(evt)

    def poll(self):
        """
        Reads messages from the bus until either stop event message or KeyboardInterrupt
        """

        if not self.on_message:
            logger.warning('No message handlers installed, cannot poll')
            return

        stop=False
        while not stop:
            msg = self.get()
            if msg.timestamp and time.time() - msg.timestamp > self._MSG_EXPIRY_TIMEOUT:
                logger.debug('{} seconds old message on the bus expired, ignoring it: {}'
                            .format(int(time.time()-msg.timestamp), msg))
                continue

            try:
                self.on_message(msg)
            except Exception as e:
                logger.error('Error on processing message {}'.format(msg))
                logger.exception(e)

            if isinstance(msg, StopEvent) and msg.targets_me():
                logger.info('Received STOP event on the bus')
                stop=True


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