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# Copyright 2015, Google Inc.
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met:
#
# * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# * Redistributions in binary form must reproduce the above
# copyright notice, this list of conditions and the following disclaimer
# in the documentation and/or other materials provided with the
# distribution.
# * Neither the name of Google Inc. nor the names of its
# contributors may be used to endorse or promote products derived from
# this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
"""Affords a connectivity-state-listenable channel."""
import threading
import time
from grpc._adapter import _low
from grpc._adapter import _types
from grpc.beta import interfaces
from grpc.framework.foundation import callable_util
_CHANNEL_SUBSCRIPTION_CALLBACK_ERROR_LOG_MESSAGE = (
'Exception calling channel subscription callback!')
_LOW_CONNECTIVITY_STATE_TO_CHANNEL_CONNECTIVITY = {
state: connectivity for state, connectivity in zip(
_types.ConnectivityState, interfaces.ChannelConnectivity)
}
class ConnectivityChannel(object):
def __init__(self, low_channel):
self._lock = threading.Lock()
self._low_channel = low_channel
self._polling = False
self._connectivity = None
self._try_to_connect = False
self._callbacks_and_connectivities = []
self._delivering = False
def _deliveries(self, connectivity):
callbacks_needing_update = []
for callback_and_connectivity in self._callbacks_and_connectivities:
callback, callback_connectivity = callback_and_connectivity
if callback_connectivity is not connectivity:
callbacks_needing_update.append(callback)
callback_and_connectivity[1] = connectivity
return callbacks_needing_update
def _deliver(self, initial_connectivity, initial_callbacks):
connectivity = initial_connectivity
callbacks = initial_callbacks
while True:
for callback in callbacks:
callable_util.call_logging_exceptions(
callback, _CHANNEL_SUBSCRIPTION_CALLBACK_ERROR_LOG_MESSAGE,
connectivity)
with self._lock:
callbacks = self._deliveries(self._connectivity)
if callbacks:
connectivity = self._connectivity
else:
self._delivering = False
return
def _spawn_delivery(self, connectivity, callbacks):
delivering_thread = threading.Thread(
target=self._deliver, args=(connectivity, callbacks,))
delivering_thread.start()
self._delivering = True
# TODO(issue 3064): Don't poll.
def _poll_connectivity(self, low_channel, initial_try_to_connect):
try_to_connect = initial_try_to_connect
low_connectivity = low_channel.check_connectivity_state(try_to_connect)
with self._lock:
self._connectivity = _LOW_CONNECTIVITY_STATE_TO_CHANNEL_CONNECTIVITY[
low_connectivity]
callbacks = tuple(
callback for callback, unused_but_known_to_be_none_connectivity
in self._callbacks_and_connectivities)
for callback_and_connectivity in self._callbacks_and_connectivities:
callback_and_connectivity[1] = self._connectivity
if callbacks:
self._spawn_delivery(self._connectivity, callbacks)
completion_queue = _low.CompletionQueue()
while True:
low_channel.watch_connectivity_state(
low_connectivity, time.time() + 0.2, completion_queue, None)
event = completion_queue.next()
with self._lock:
if not self._callbacks_and_connectivities and not self._try_to_connect:
self._polling = False
self._connectivity = None
completion_queue.shutdown()
break
try_to_connect = self._try_to_connect
self._try_to_connect = False
if event.success or try_to_connect:
low_connectivity = low_channel.check_connectivity_state(try_to_connect)
with self._lock:
self._connectivity = _LOW_CONNECTIVITY_STATE_TO_CHANNEL_CONNECTIVITY[
low_connectivity]
if not self._delivering:
callbacks = self._deliveries(self._connectivity)
if callbacks:
self._spawn_delivery(self._connectivity, callbacks)
def subscribe(self, callback, try_to_connect):
with self._lock:
if not self._callbacks_and_connectivities and not self._polling:
polling_thread = threading.Thread(
target=self._poll_connectivity,
args=(self._low_channel, bool(try_to_connect)))
polling_thread.start()
self._polling = True
self._callbacks_and_connectivities.append([callback, None])
elif not self._delivering and self._connectivity is not None:
self._spawn_delivery(self._connectivity, (callback,))
self._try_to_connect |= bool(try_to_connect)
self._callbacks_and_connectivities.append(
[callback, self._connectivity])
else:
self._try_to_connect |= bool(try_to_connect)
self._callbacks_and_connectivities.append([callback, None])
def unsubscribe(self, callback):
with self._lock:
for index, (subscribed_callback, unused_connectivity) in enumerate(
self._callbacks_and_connectivities):
if callback == subscribed_callback:
self._callbacks_and_connectivities.pop(index)
break
def low_channel(self):
return self._low_channel
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