| # 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. |
| """Helpful utilities related to the stream module.""" |
| |
| import logging |
| import threading |
| |
| from grpc.framework.foundation import stream |
| |
| _NO_VALUE = object() |
| _LOGGER = logging.getLogger(__name__) |
| _LOGGER.addHandler(logging.NullHandler()) |
| |
| |
| class TransformingConsumer(stream.Consumer): |
| """A stream.Consumer that passes a transformation of its input to another.""" |
| |
| def __init__(self, transformation, downstream): |
| self._transformation = transformation |
| self._downstream = downstream |
| |
| def consume(self, value): |
| self._downstream.consume(self._transformation(value)) |
| |
| def terminate(self): |
| self._downstream.terminate() |
| |
| def consume_and_terminate(self, value): |
| self._downstream.consume_and_terminate(self._transformation(value)) |
| |
| |
| class IterableConsumer(stream.Consumer): |
| """A Consumer that when iterated over emits the values it has consumed.""" |
| |
| def __init__(self): |
| self._condition = threading.Condition() |
| self._values = [] |
| self._active = True |
| |
| def consume(self, value): |
| with self._condition: |
| if self._active: |
| self._values.append(value) |
| self._condition.notify() |
| |
| def terminate(self): |
| with self._condition: |
| self._active = False |
| self._condition.notify() |
| |
| def consume_and_terminate(self, value): |
| with self._condition: |
| if self._active: |
| self._values.append(value) |
| self._active = False |
| self._condition.notify() |
| |
| def __iter__(self): |
| return self |
| |
| def __next__(self): |
| return self.next() |
| |
| def next(self): |
| with self._condition: |
| while self._active and not self._values: |
| self._condition.wait() |
| if self._values: |
| return self._values.pop(0) |
| else: |
| raise StopIteration() |
| |
| |
| class ThreadSwitchingConsumer(stream.Consumer): |
| """A Consumer decorator that affords serialization and asynchrony.""" |
| |
| def __init__(self, sink, pool): |
| self._lock = threading.Lock() |
| self._sink = sink |
| self._pool = pool |
| # True if self._spin has been submitted to the pool to be called once and |
| # that call has not yet returned, False otherwise. |
| self._spinning = False |
| self._values = [] |
| self._active = True |
| |
| def _spin(self, sink, value, terminate): |
| while True: |
| try: |
| if value is _NO_VALUE: |
| sink.terminate() |
| elif terminate: |
| sink.consume_and_terminate(value) |
| else: |
| sink.consume(value) |
| except Exception as e: # pylint:disable=broad-except |
| _LOGGER.exception(e) |
| |
| with self._lock: |
| if terminate: |
| self._spinning = False |
| return |
| elif self._values: |
| value = self._values.pop(0) |
| terminate = not self._values and not self._active |
| elif not self._active: |
| value = _NO_VALUE |
| terminate = True |
| else: |
| self._spinning = False |
| return |
| |
| def consume(self, value): |
| with self._lock: |
| if self._active: |
| if self._spinning: |
| self._values.append(value) |
| else: |
| self._pool.submit(self._spin, self._sink, value, False) |
| self._spinning = True |
| |
| def terminate(self): |
| with self._lock: |
| if self._active: |
| self._active = False |
| if not self._spinning: |
| self._pool.submit(self._spin, self._sink, _NO_VALUE, True) |
| self._spinning = True |
| |
| def consume_and_terminate(self, value): |
| with self._lock: |
| if self._active: |
| self._active = False |
| if self._spinning: |
| self._values.append(value) |
| else: |
| self._pool.submit(self._spin, self._sink, value, True) |
| self._spinning = True |