baseimage-tutorial-framework/lib/tfw/networking/server/tfw_server.py

# Copyright (C) 2018 Avatao.com Innovative Learning Kft.
# All Rights Reserved. See LICENSE file for details.

from abc import ABC, abstractmethod

from tornado.web import Application

from tfw.networking.event_handlers import ServerUplinkConnector
from tfw.networking.server import EventHandlerConnector
from tfw.networking import MessageSender
from tfw.config.logs import logging
from .zmq_websocket_proxy import ZMQWebSocketProxy

LOG = logging.getLogger(__name__)


class TFWServer:
    """
    This class handles the proxying of messages between the frontend and event handers.
    It proxies messages from the "/ws" route to all event handlers subscribed to a ZMQ
    SUB socket.
    """
    def __init__(self):
        self._event_handler_connector = EventHandlerConnector()
        self._uplink_connector = ServerUplinkConnector()

        self.application = Application([(
            r'/ws', ZMQWebSocketProxy,{
                'event_handler_connector': self._event_handler_connector,
                'message_handlers': [self.handle_trigger, self.handle_recover],
                'frontend_message_handlers': [self.save_frontend_messages]
            })]
        )

        self._frontend_messages = FrontendMessageStorage()

    def handle_trigger(self, message):
        if 'trigger' in message:
            LOG.debug('Executing handler for trigger "%s"', message.get('trigger', ''))
            self._uplink_connector.send_to_eventhandler({
                'key': 'fsm',
                'data': {
                    'command': 'trigger',
                    'value': message.get('trigger', '')
                }
            })

    def handle_recover(self, message):
        if message['key'] == 'recover':
            self._frontend_messages.replay_messages(self._uplink_connector)

    def save_frontend_messages(self, message):
        self._frontend_messages.save_message(message)

    def listen(self, port):
        self.application.listen(port)


class MessageStorage(ABC):
    def __init__(self):
        self.saved_messages = []

    def save_message(self, message):
        if self.filter_message(message):
            self.saved_messages.extend(self.transform_message(message))

    @abstractmethod
    def filter_message(self, message):
        raise NotImplementedError

    def transform_message(self, message):
        yield message


class FrontendMessageStorage(MessageStorage):
    def filter_message(self, message):
        return message['key'] in ('message', 'dashboard', 'queueMessages')

    def transform_message(self, message):
        if message['key'] == 'queueMessages':
            yield from MessageSender.generate_messages_from_queue(message)
        else:
            yield message

    def replay_messages(self, connector):
        for message in self.saved_messages:
            connector.send(message)