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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 Future implementation based on Python's threading.Timer."""
import sys
import threading
import time
from grpc.framework.foundation import future
class TimerFuture(future.Future):
"""A Future implementation based around Timer objects."""
def __init__(self, compute_time, computation):
"""Constructor.
Args:
compute_time: The time after which to begin this future's computation.
computation: The computation to be performed within this Future.
"""
self._lock = threading.Lock()
self._compute_time = compute_time
self._computation = computation
self._timer = None
self._computing = False
self._computed = False
self._cancelled = False
self._result = None
self._exception = None
self._traceback = None
self._waiting = []
def _compute(self):
"""Performs the computation embedded in this Future.
Or doesn't, if the time to perform it has not yet arrived.
"""
with self._lock:
time_remaining = self._compute_time - time.time()
if 0 < time_remaining:
self._timer = threading.Timer(time_remaining, self._compute)
self._timer.start()
return
else:
self._computing = True
try:
return_value = self._computation()
exception = None
traceback = None
except Exception as e: # pylint: disable=broad-except
return_value = None
exception = e
traceback = sys.exc_info()[2]
with self._lock:
self._computing = False
self._computed = True
self._return_value = return_value
self._exception = exception
self._traceback = traceback
waiting = self._waiting
for callback in waiting:
callback(self)
def start(self):
"""Starts this Future.
This must be called exactly once, immediately after construction.
"""
with self._lock:
self._timer = threading.Timer(
self._compute_time - time.time(), self._compute)
self._timer.start()
def cancel(self):
"""See future.Future.cancel for specification."""
with self._lock:
if self._computing or self._computed:
return False
elif self._cancelled:
return True
else:
self._timer.cancel()
self._cancelled = True
waiting = self._waiting
for callback in waiting:
try:
callback(self)
except Exception: # pylint: disable=broad-except
pass
return True
def cancelled(self):
"""See future.Future.cancelled for specification."""
with self._lock:
return self._cancelled
def running(self):
"""See future.Future.running for specification."""
with self._lock:
return not self._computed and not self._cancelled
def done(self):
"""See future.Future.done for specification."""
with self._lock:
return self._computed or self._cancelled
def result(self, timeout=None):
"""See future.Future.result for specification."""
with self._lock:
if self._cancelled:
raise future.CancelledError()
elif self._computed:
if self._exception is None:
return self._return_value
else:
raise self._exception # pylint: disable=raising-bad-type
condition = threading.Condition()
def notify_condition(unused_future):
with condition:
condition.notify()
self._waiting.append(notify_condition)
with condition:
condition.wait(timeout=timeout)
with self._lock:
if self._cancelled:
raise future.CancelledError()
elif self._computed:
if self._exception is None:
return self._return_value
else:
raise self._exception # pylint: disable=raising-bad-type
else:
raise future.TimeoutError()
def exception(self, timeout=None):
"""See future.Future.exception for specification."""
with self._lock:
if self._cancelled:
raise future.CancelledError()
elif self._computed:
return self._exception
condition = threading.Condition()
def notify_condition(unused_future):
with condition:
condition.notify()
self._waiting.append(notify_condition)
with condition:
condition.wait(timeout=timeout)
with self._lock:
if self._cancelled:
raise future.CancelledError()
elif self._computed:
return self._exception
else:
raise future.TimeoutError()
def traceback(self, timeout=None):
"""See future.Future.traceback for specification."""
with self._lock:
if self._cancelled:
raise future.CancelledError()
elif self._computed:
return self._traceback
condition = threading.Condition()
def notify_condition(unused_future):
with condition:
condition.notify()
self._waiting.append(notify_condition)
with condition:
condition.wait(timeout=timeout)
with self._lock:
if self._cancelled:
raise future.CancelledError()
elif self._computed:
return self._traceback
else:
raise future.TimeoutError()
def add_done_callback(self, fn):
"""See future.Future.add_done_callback for specification."""
with self._lock:
if not self._computed and not self._cancelled:
self._waiting.append(fn)
return
fn(self)
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