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# Copyright 2015 gRPC authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Utilities for the gRPC Python Beta API."""
import threading
import time
# implementations is referenced from specification in this module.
from grpc.beta import implementations # pylint: disable=unused-import
from grpc.beta import interfaces
from grpc.framework.foundation import callable_util
from grpc.framework.foundation import future
_DONE_CALLBACK_EXCEPTION_LOG_MESSAGE = (
'Exception calling connectivity future "done" callback!')
class _ChannelReadyFuture(future.Future):
def __init__(self, channel):
self._condition = threading.Condition()
self._channel = channel
self._matured = False
self._cancelled = False
self._done_callbacks = []
def _block(self, timeout):
until = None if timeout is None else time.time() + timeout
with self._condition:
while True:
if self._cancelled:
raise future.CancelledError()
elif self._matured:
return
else:
if until is None:
self._condition.wait()
else:
remaining = until - time.time()
if remaining < 0:
raise future.TimeoutError()
else:
self._condition.wait(timeout=remaining)
def _update(self, connectivity):
with self._condition:
if (not self._cancelled and
connectivity is interfaces.ChannelConnectivity.READY):
self._matured = True
self._channel.unsubscribe(self._update)
self._condition.notify_all()
done_callbacks = tuple(self._done_callbacks)
self._done_callbacks = None
else:
return
for done_callback in done_callbacks:
callable_util.call_logging_exceptions(
done_callback, _DONE_CALLBACK_EXCEPTION_LOG_MESSAGE, self)
def cancel(self):
with self._condition:
if not self._matured:
self._cancelled = True
self._channel.unsubscribe(self._update)
self._condition.notify_all()
done_callbacks = tuple(self._done_callbacks)
self._done_callbacks = None
else:
return False
for done_callback in done_callbacks:
callable_util.call_logging_exceptions(
done_callback, _DONE_CALLBACK_EXCEPTION_LOG_MESSAGE, self)
return True
def cancelled(self):
with self._condition:
return self._cancelled
def running(self):
with self._condition:
return not self._cancelled and not self._matured
def done(self):
with self._condition:
return self._cancelled or self._matured
def result(self, timeout=None):
self._block(timeout)
return None
def exception(self, timeout=None):
self._block(timeout)
return None
def traceback(self, timeout=None):
self._block(timeout)
return None
def add_done_callback(self, fn):
with self._condition:
if not self._cancelled and not self._matured:
self._done_callbacks.append(fn)
return
fn(self)
def start(self):
with self._condition:
self._channel.subscribe(self._update, try_to_connect=True)
def __del__(self):
with self._condition:
if not self._cancelled and not self._matured:
self._channel.unsubscribe(self._update)
def channel_ready_future(channel):
"""Creates a future.Future tracking when an implementations.Channel is ready.
Cancelling the returned future.Future does not tell the given
implementations.Channel to abandon attempts it may have been making to
connect; cancelling merely deactivates the return future.Future's
subscription to the given implementations.Channel's connectivity.
Args:
channel: An implementations.Channel.
Returns:
A future.Future that matures when the given Channel has connectivity
interfaces.ChannelConnectivity.READY.
"""
ready_future = _ChannelReadyFuture(channel)
ready_future.start()
return ready_future
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