platypush/platypush/backend/local/__init__.py

import logging
import json
import os
import time
import threading

from .. import Backend

from platypush.message import Message
from platypush.message.event import StopEvent
from platypush.message.request import Request
from platypush.message.response import Response

class LocalBackend(Backend):
    """ Sends and receive messages on two distinct local FIFOs, one for
    the requests and one for the responses """

    def __init__(self, request_fifo, response_fifo, **kwargs):
        super().__init__(**kwargs)

        self.request_fifo  = request_fifo
        self.response_fifo = response_fifo

        try: os.mkfifo(self.request_fifo)
        except FileExistsError as e: pass

        try: os.mkfifo(self.response_fifo)
        except FileExistsError as e: pass


    def send_message(self, msg):
        fifo = self.response_fifo \
            if isinstance(msg, Response) or self._request_context \
            else self.request_fifo

        msg = '{}\n'.format(str(msg)).encode('utf-8')

        with open(fifo, 'wb') as f:
            f.write(msg)


    def _get_next_message(self):
        fifo = self.response_fifo if self._request_context else self.request_fifo
        with open(fifo, 'rb', 0) as f:
            msg = f.readline()

        return Message.build(msg) if len(msg) else None


    def run(self):
        super().run()
        logging.info('Initialized local backend on {} and {}'.
                     format(self.request_fifo, self.response_fifo))

        while not self.should_stop():
            try:
                msg = self._get_next_message()
                if not msg: continue
            except Exception as e:
                logging.exception(e)
                time.sleep(0.2)
                continue

            logging.debug('Received message on the local backend: {}, thread_id: '.format(msg, self.thread_id))

            if self.should_stop(): break
            self.on_message(msg)


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