""" .. moduleauthor:: Fabio Manganiello .. license: MIT """ import logging import re import socket import threading import time from threading import Thread from typing import Optional from platypush.bus import Bus from platypush.config import Config from platypush.context import get_backend from platypush.message.event.zeroconf import ZeroconfServiceAddedEvent, ZeroconfServiceRemovedEvent from platypush.utils import set_timeout, clear_timeout, \ get_redis_queue_name_by_message, set_thread_name, get_backend_name_by_class from platypush import __version__ from platypush.event import EventGenerator from platypush.message import Message from platypush.message.event import Event, StopEvent from platypush.message.request import Request from platypush.message.response import Response class Backend(Thread, EventGenerator): """ Parent class for backends. A backend is basically a thread that checks for new events on some channel (e.g. a network socket, a queue, some new entries on an API endpoint or an RSS feed, a voice command through an assistant, a new measure from a sensor etc.) and propagates event messages to the main application bus whenever a new event happens. You can then build whichever type of custom logic you want on such events. """ _default_response_timeout = 5 # Loop function, can be implemented by derived classes loop = None def __init__(self, bus: Optional[Bus] = None, poll_seconds: Optional[float] = None, **kwargs): """ :param bus: Reference to the bus object to be used in the backend :param poll_seconds: If the backend implements a ``loop`` method, this parameter expresses how often the loop should run in seconds. :param kwargs: Key-value configuration for the backend """ self._thread_name = self.__class__.__name__ EventGenerator.__init__(self) Thread.__init__(self, name=self._thread_name, daemon=True) # If no bus is specified, create an internal queue where # the received messages will be pushed self.bus = bus or Bus() self.poll_seconds = float(poll_seconds) if poll_seconds else None self.device_id = Config.get('device_id') self.thread_id = None self._should_stop = False self._stop_event = threading.Event() self._kwargs = kwargs self.logger = logging.getLogger('platypush:backend:' + get_backend_name_by_class(self.__class__)) self.zeroconf = None self.zeroconf_info = None # Internal-only, we set the request context on a backend if that # backend is intended to react for a response to a specific request self._request_context = kwargs['_req_ctx'] if '_req_ctx' in kwargs \ else None if 'logging' in kwargs: self.logger.setLevel(getattr(logging, kwargs.get('logging').upper())) def on_message(self, msg): """ Callback when a message is received on the backend. It parses and posts the message on the main bus. It should be called by the derived classes whenever a new message should be processed. :param msg: Received message. It can be either a key-value dictionary, a platypush.message.Message object, or a string/byte UTF-8 encoded string """ msg = Message.build(msg) if not getattr(msg, 'target') or msg.target != self.device_id: return # Not for me self.logger.debug('Message received on the {} backend: {}'.format( self.__class__.__name__, msg)) if self._is_expected_response(msg): # Expected response, trigger the response handler clear_timeout() self._request_context['on_response'](msg) self.stop() return if isinstance(msg, StopEvent) and msg.targets_me(): self.logger.info('Received STOP event on {}'.format(self.__class__.__name__)) self._should_stop = True else: msg.backend = self # Augment message to be able to process responses self.bus.post(msg) def _is_expected_response(self, msg): """ Internal only - returns true if we are expecting for a response and msg is that response """ return self._request_context \ and isinstance(msg, Response) \ and msg.id == self._request_context['request'].id def _get_backend_config(self): config_name = 'backend.' + self.__class__.__name__.split('Backend')[0].lower() return Config.get(config_name) def _setup_response_handler(self, request, on_response, response_timeout): def _timeout_hndl(): raise RuntimeError('Timed out while waiting for a response from {}'. format(request.target)) req_ctx = { 'request': request, 'on_response': on_response, 'response_timeout': response_timeout, } resp_backend = self.__class__(bus=self.bus, _req_ctx=req_ctx, **self._get_backend_config(), **self._kwargs) # Set the response timeout if response_timeout: set_timeout(seconds=response_timeout, on_timeout=_timeout_hndl) resp_backend.start() def send_event(self, event, **kwargs): """ Send an event message on the backend. :param event: Event to send. It can be a dict, a string/bytes UTF-8 JSON, or a platypush.message.event.Event object. """ event = Event.build(event) assert isinstance(event, Event) event.origin = self.device_id if not hasattr(event, 'target'): event.target = self.device_id self.send_message(event, **kwargs) def send_request(self, request, on_response=None, response_timeout=_default_response_timeout, **kwargs): """ Send a request message on the backend. :param request: The request, either a dict, a string/bytes UTF-8 JSON, or a platypush.message.request.Request object. :param on_response: Optional callback that will be called when a response is received. If set, this method will synchronously wait for a response before exiting. :type on_response: function :param response_timeout: If on_response is set, the backend will raise an exception if the response isn't received within this number of seconds (default: None) :type response_timeout: float """ request = Request.build(request) assert isinstance(request, Request) request.origin = self.device_id if on_response and response_timeout != 0: self._setup_response_handler(request, on_response, response_timeout) self.send_message(request, **kwargs) def send_response(self, response, request, **kwargs): """ Send a response message on the backend. :param response: The response, either a dict, a string/bytes UTF-8 JSON, or a :class:`platypush.message.response.Response` object. :param request: Associated request, used to set the response parameters that will link them """ assert isinstance(response, Response) assert isinstance(request, Request) self.send_message(response, **kwargs) def send_message(self, msg, queue_name=None, **kwargs): """ Sends a platypush.message.Message to a node. To be implemented in the derived classes. By default, if the Redis backend is configured then it will try to deliver the message to other consumers through the configured Redis main queue. :param msg: The message to send :param queue_name: Send the message on a specific queue (default: the queue_name configured on the Redis backend) """ try: redis = get_backend('redis') if not redis: raise KeyError() except KeyError: self.logger.warning("Backend {} does not implement send_message " + "and the fallback Redis backend isn't configured") return redis.send_message(msg, queue_name=queue_name) def run(self): """ Starts the backend thread. To be implemented in the derived classes if the loop method isn't defined. """ self.thread_id = threading.get_ident() set_thread_name(self._thread_name) if not callable(self.loop): return while not self.should_stop(): try: with self: has_error = False while not self.should_stop() and not has_error: try: self.loop() except Exception as e: has_error = True self.logger.error(str(e)) self.logger.exception(e) finally: if self.poll_seconds: time.sleep(self.poll_seconds) elif has_error: time.sleep(5) except Exception as e: self.logger.error('{} initialization error: {}'.format(self.__class__.__name__, str(e))) self.logger.exception(e) time.sleep(self.poll_seconds or 5) def __enter__(self): """ Invoked when the backend is initialized, if the main logic is within a ``loop()`` function """ self.logger.info('Initialized backend {}'.format(self.__class__.__name__)) def __exit__(self, exc_type, exc_val, exc_tb): """ Invoked when the backend is terminated, if the main logic is within a ``loop()`` function """ self.on_stop() self.logger.info('Terminated backend {}'.format(self.__class__.__name__)) def on_stop(self): """ Callback invoked when the process stops """ self.unregister_service() def stop(self): """ Stops the backend thread by sending a STOP event on its bus """ def _async_stop(): evt = StopEvent(target=self.device_id, origin=self.device_id, thread_id=self.thread_id) self.send_message(evt) self._stop_event.set() self.on_stop() Thread(target=_async_stop).start() def should_stop(self): return self._should_stop def wait_stop(self, timeout=None) -> bool: return self._stop_event.wait(timeout) def _get_redis(self): import redis redis_backend = get_backend('redis') if not redis_backend: self.logger.warning('Redis backend not configured - some ' + 'web server features may not be working properly') redis_args = {} else: redis_args = redis_backend.redis_args redis = redis.Redis(**redis_args) return redis def get_message_response(self, msg): try: redis = self._get_redis() response = redis.blpop(get_redis_queue_name_by_message(msg), timeout=60) if response and len(response) > 1: response = Message.build(response[1]) else: response = None return response except Exception as e: self.logger.error('Error while processing response to {}: {}'.format(msg, str(e))) @staticmethod def _get_ip() -> str: """ Get the IP address of the machine. """ s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) s.connect(('8.8.8.8', 80)) addr = s.getsockname()[0] s.close() return addr def register_service(self, port: Optional[int] = None, name: Optional[str] = None, udp: bool = False): """ Initialize the Zeroconf service configuration for this backend. """ try: from zeroconf import ServiceInfo, Zeroconf from platypush.plugins.zeroconf import ZeroconfListener except ImportError: self.logger.warning('zeroconf package not available, service discovery will be disabled.') return self.zeroconf = Zeroconf() srv_desc = { 'name': 'Platypush', 'vendor': 'Platypush', 'version': __version__, } name = name or re.sub(r'Backend$', '', self.__class__.__name__).lower() srv_type = '_platypush-{name}._{proto}.local.'.format(name=name, proto='udp' if udp else 'tcp') srv_name = '{host}.{type}'.format(host=self.device_id, type=srv_type) if port: srv_port = port else: srv_port = self.port if hasattr(self, 'port') else None self.zeroconf_info = ServiceInfo(srv_type, srv_name, addresses=[socket.inet_aton(self._get_ip())], port=srv_port, weight=0, priority=0, properties=srv_desc) self.zeroconf.register_service(self.zeroconf_info) self.bus.post(ZeroconfServiceAddedEvent(service_type=srv_type, service_name=srv_name, service_info=ZeroconfListener.parse_service_info(self.zeroconf_info))) def unregister_service(self): """ Unregister the Zeroconf service configuration if available. """ if self.zeroconf and self.zeroconf_info: self.zeroconf.unregister_service(self.zeroconf_info) if self.zeroconf: self.zeroconf.close() if self.zeroconf_info: self.bus.post(ZeroconfServiceRemovedEvent(service_type=self.zeroconf_info.type, service_name=self.zeroconf_info.name)) else: self.bus.post(ZeroconfServiceRemovedEvent(service_type=None, service_name=None)) self.zeroconf_info = None self.zeroconf = None # vim:sw=4:ts=4:et: