From 1e342cc8a57591914930c663973d1ccb3a7a69d1 Mon Sep 17 00:00:00 2001 From: Fabio Manganiello Date: Sat, 11 Jan 2020 18:13:25 +0100 Subject: [PATCH] New interface for implementing backends. Backends that simply poll for changes and wait some time between checks can just implement a `loop()` method and, optionally, `__enter__` and `__exit__` methods, so they can perform initialization/cleanup logic within a context manager. --- platypush/backend/__init__.py | 35 +++++++++++++++++++++++++++---- platypush/backend/foursquare.py | 37 +++++++++++++++------------------ 2 files changed, 48 insertions(+), 24 deletions(-) diff --git a/platypush/backend/__init__.py b/platypush/backend/__init__.py index e81356b197..0cb939cea2 100644 --- a/platypush/backend/__init__.py +++ b/platypush/backend/__init__.py @@ -5,8 +5,10 @@ import logging import threading +import time from threading import Thread +from typing import Optional from platypush.bus import Bus from platypush.config import Config @@ -35,13 +37,15 @@ class Backend(Thread, EventGenerator): _default_response_timeout = 5 - def __init__(self, bus=None, **kwargs): + # 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 - :type bus: platypush.bus.Bus - + :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 - :type kwargs: dict """ self._thread_name = self.__class__.__name__ @@ -51,6 +55,7 @@ class Backend(Thread, EventGenerator): # 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 @@ -218,6 +223,28 @@ class Backend(Thread, EventGenerator): """ Starts the backend thread. To be implemented in the derived classes """ self.thread_id = threading.get_ident() set_thread_name(self._thread_name) + if not callable(self.loop): + return + + with self: + while not self.should_stop(): + try: + self.loop() + except Exception as e: + self.logger.error(str(e)) + self.logger.exception(e) + finally: + if self.poll_seconds: + time.sleep(self.poll_seconds) + + 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 """ diff --git a/platypush/backend/foursquare.py b/platypush/backend/foursquare.py index c75581e03e..f560efe52f 100644 --- a/platypush/backend/foursquare.py +++ b/platypush/backend/foursquare.py @@ -1,4 +1,4 @@ -import time +from typing import Optional from platypush.backend import Backend from platypush.context import get_plugin @@ -22,34 +22,31 @@ class FoursquareBackend(Backend): _last_created_at_varname = '_foursquare_checkin_last_created_at' - def __init__(self, poll_seconds: float = 60.0, *args, **kwargs): + def __init__(self, poll_seconds: Optional[float] = 60.0, *args, **kwargs): """ :param poll_seconds: How often the backend should check for new check-ins (default: one minute). """ - super().__init__(*args, **kwargs) - self.poll_seconds = poll_seconds + super().__init__(*args, poll_seconds=poll_seconds, **kwargs) self._last_created_at = None - def run(self): - super().run() + def __enter__(self): self._last_created_at = int(get_plugin('variable').get(self._last_created_at_varname). output.get(self._last_created_at_varname) or 0) self.logger.info('Started Foursquare backend') - while not self.should_stop(): - try: - checkins = get_plugin('foursquare').get_checkins().output - if checkins: - last_checkin = checkins[0] - if not self._last_created_at or last_checkin.get('createdAt', 0) > self._last_created_at: - self.bus.post(FoursquareCheckinEvent(checkin=last_checkin)) - self._last_created_at = last_checkin.get('createdAt', 0) - get_plugin('variable').set(**{self._last_created_at_varname: self._last_created_at}) - except Exception as e: - self.logger.error('Error while retrieving the list of checkins: {}'.format(str(e))) - self.logger.exception(e) - finally: - time.sleep(self.poll_seconds) + def loop(self): + checkins = get_plugin('foursquare').get_checkins().output + if not checkins: + return + + last_checkin = checkins[0] + last_checkin_created_at = last_checkin.get('createdAt', 0) + if self._last_created_at and last_checkin_created_at <= self._last_created_at: + return + + self.bus.post(FoursquareCheckinEvent(checkin=last_checkin)) + self._last_created_at = last_checkin_created_at + get_plugin('variable').set(**{self._last_created_at_varname: self._last_created_at}) # vim:sw=4:ts=4:et: