services/nodemanager/arvnodeman/clientactor.py

   1 #!/usr/bin/env python
   2
   3 from __future__ import absolute_import, print_function
   4
   5 import logging
   6 import time
   7
   8 import pykka
   9
  10 from .config import actor_class
  11
  12 def _notify_subscribers(response, subscribers):
  13     """Send the response to all the subscriber methods.
  14
  15     If any of the subscriber actors have stopped, remove them from the
  16     subscriber set.
  17     """
  18     dead_subscribers = set()
  19     for subscriber in subscribers:
  20         try:
  21             subscriber(response)
  22         except pykka.ActorDeadError:
  23             dead_subscribers.add(subscriber)
  24     subscribers.difference_update(dead_subscribers)
  25
  26 class RemotePollLoopActor(actor_class):
  27     """Abstract actor class to regularly poll a remote service.
  28
  29     This actor sends regular requests to a remote service, and sends each
  30     response to subscribers.  It takes care of error handling, and retrying
  31     requests with exponential backoff.
  32
  33     To use this actor, define CLIENT_ERRORS and the _send_request method.
  34     If you also define an _item_key method, this class will support
  35     subscribing to a specific item by key in responses.
  36     """
  37     CLIENT_ERRORS = ()
  38
  39     def __init__(self, client, timer_actor, poll_wait=60, max_poll_wait=180):
  40         super(RemotePollLoopActor, self).__init__()
  41         self._client = client
  42         self._timer = timer_actor
  43         self._logger = logging.getLogger(self.LOGGER_NAME)
  44         self._later = self.actor_ref.proxy()
  45         self._polling_started = False
  46         self.log_prefix = "{} (at {})".format(self.__class__.__name__, id(self))
  47         self.min_poll_wait = poll_wait
  48         self.max_poll_wait = max_poll_wait
  49         self.poll_wait = self.min_poll_wait
  50         self.all_subscribers = set()
  51         self.key_subscribers = {}
  52         if hasattr(self, '_item_key'):
  53             self.subscribe_to = self._subscribe_to
  54
  55     def _start_polling(self):
  56         if not self._polling_started:
  57             self._polling_started = True
  58             self._later.poll()
  59
  60     def subscribe(self, subscriber):
  61         self.all_subscribers.add(subscriber)
  62         self._logger.debug("%r subscribed to all events", subscriber)
  63         self._start_polling()
  64
  65     # __init__ exposes this method to the proxy if the subclass defines
  66     # _item_key.
  67     def _subscribe_to(self, key, subscriber):
  68         self.key_subscribers.setdefault(key, set()).add(subscriber)
  69         self._logger.debug("%r subscribed to events for '%s'", subscriber, key)
  70         self._start_polling()
  71
  72     def _send_request(self):
  73         raise NotImplementedError("subclasses must implement request method")
  74
  75     def _got_response(self, response):
  76         self._logger.debug("%s got response with %d items",
  77                            self.log_prefix, len(response))
  78         self.poll_wait = self.min_poll_wait
  79         _notify_subscribers(response, self.all_subscribers)
  80         if hasattr(self, '_item_key'):
  81             items = {self._item_key(x): x for x in response}
  82             for key, subscribers in self.key_subscribers.iteritems():
  83                 _notify_subscribers(items.get(key), subscribers)
  84
  85     def _got_error(self, error):
  86         self.poll_wait = min(self.poll_wait * 2, self.max_poll_wait)
  87         return "{} got error: {} - waiting {} seconds".format(
  88             self.log_prefix, error, self.poll_wait)
  89
  90     def poll(self, scheduled_start=None):
  91         self._logger.debug("%s sending poll", self.log_prefix)
  92         start_time = time.time()
  93         if scheduled_start is None:
  94             scheduled_start = start_time
  95         try:
  96             response = self._send_request()
  97         except Exception as error:
  98             errmsg = self._got_error(error)
  99             if isinstance(error, self.CLIENT_ERRORS):
 100                 self._logger.warning(errmsg)
 101             else:
 102                 self._logger.exception(errmsg)
 103             next_poll = start_time + self.poll_wait
 104         else:
 105             self._got_response(response)
 106             next_poll = scheduled_start + self.poll_wait
 107         end_time = time.time()
 108         if next_poll < end_time:  # We've drifted too much; start fresh.
 109             next_poll = end_time + self.poll_wait
 110         self._timer.schedule(next_poll, self._later.poll, next_poll)