| # 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. |
| |
| """Implementations of in-order work deference.""" |
| |
| import abc |
| import enum |
| import threading |
| |
| from grpc.framework.foundation import activated |
| from grpc.framework.foundation import logging_pool |
| |
| _NULL_BEHAVIOR = lambda unused_value: None |
| |
| |
| class Relay(object): |
| """Performs work submitted to it in another thread. |
| |
| Performs work in the order in which work was submitted to it; otherwise there |
| would be no reason to use an implementation of this interface instead of a |
| thread pool. |
| """ |
| |
| @abc.abstractmethod |
| def add_value(self, value): |
| """Adds a value to be passed to the behavior registered with this Relay. |
| |
| Args: |
| value: A value that will be passed to a call made in another thread to the |
| behavior registered with this Relay. |
| """ |
| raise NotImplementedError() |
| |
| @abc.abstractmethod |
| def set_behavior(self, behavior): |
| """Sets the behavior that this Relay should call when passed values. |
| |
| Args: |
| behavior: The behavior that this Relay should call in another thread when |
| passed a value, or None to have passed values ignored. |
| """ |
| raise NotImplementedError() |
| |
| |
| class _PoolRelay(activated.Activated, Relay): |
| |
| @enum.unique |
| class _State(enum.Enum): |
| INACTIVE = 'inactive' |
| IDLE = 'idle' |
| SPINNING = 'spinning' |
| |
| def __init__(self, pool, behavior): |
| self._condition = threading.Condition() |
| self._pool = pool |
| self._own_pool = pool is None |
| self._state = _PoolRelay._State.INACTIVE |
| self._activated = False |
| self._spinning = False |
| self._values = [] |
| self._behavior = _NULL_BEHAVIOR if behavior is None else behavior |
| |
| def _spin(self, behavior, value): |
| while True: |
| behavior(value) |
| with self._condition: |
| if self._values: |
| value = self._values.pop(0) |
| behavior = self._behavior |
| else: |
| self._state = _PoolRelay._State.IDLE |
| self._condition.notify_all() |
| break |
| |
| def add_value(self, value): |
| with self._condition: |
| if self._state is _PoolRelay._State.INACTIVE: |
| raise ValueError('add_value not valid on inactive Relay!') |
| elif self._state is _PoolRelay._State.IDLE: |
| self._pool.submit(self._spin, self._behavior, value) |
| self._state = _PoolRelay._State.SPINNING |
| else: |
| self._values.append(value) |
| |
| def set_behavior(self, behavior): |
| with self._condition: |
| self._behavior = _NULL_BEHAVIOR if behavior is None else behavior |
| |
| def _start(self): |
| with self._condition: |
| self._state = _PoolRelay._State.IDLE |
| if self._own_pool: |
| self._pool = logging_pool.pool(1) |
| return self |
| |
| def _stop(self): |
| with self._condition: |
| while self._state is _PoolRelay._State.SPINNING: |
| self._condition.wait() |
| if self._own_pool: |
| self._pool.shutdown(wait=True) |
| self._state = _PoolRelay._State.INACTIVE |
| |
| def __enter__(self): |
| return self._start() |
| |
| def __exit__(self, exc_type, exc_val, exc_tb): |
| self._stop() |
| return False |
| |
| def start(self): |
| return self._start() |
| |
| def stop(self): |
| self._stop() |
| |
| |
| def relay(behavior): |
| """Creates a Relay. |
| |
| Args: |
| behavior: The behavior to be called by the created Relay, or None to have |
| passed values dropped until a different behavior is given to the returned |
| Relay later. |
| |
| Returns: |
| An object that is both an activated.Activated and a Relay. The object is |
| only valid for use as a Relay when activated. |
| """ |
| return _PoolRelay(None, behavior) |
| |
| |
| def pool_relay(pool, behavior): |
| """Creates a Relay that uses a given thread pool. |
| |
| This object will make use of at most one thread in the given pool. |
| |
| Args: |
| pool: A futures.ThreadPoolExecutor for use by the created Relay. |
| behavior: The behavior to be called by the created Relay, or None to have |
| passed values dropped until a different behavior is given to the returned |
| Relay later. |
| |
| Returns: |
| An object that is both an activated.Activated and a Relay. The object is |
| only valid for use as a Relay when activated. |
| """ |
| return _PoolRelay(pool, behavior) |