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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.
"""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)
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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