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| # 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__) | |
| 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 | |