| # 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) |