tvalentyn commented on code in PR #38407: URL: https://github.com/apache/beam/pull/38407#discussion_r3211735982
########## sdks/python/apache_beam/utils/byte_limited_queue.py: ########## @@ -0,0 +1,96 @@ +# +# Licensed to the Apache Software Foundation (ASF) under one or more +# contributor license agreements. See the NOTICE file distributed with +# this work for additional information regarding copyright ownership. +# The ASF licenses this file to You 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. +# + +"""A thread-safe queue that limits capacity by total byte size.""" + +import queue +import time +from typing import Any +from typing import Callable + + +class ByteLimitedQueue(queue.Queue): + """A queue.Queue that limits by both element count and total weight. + + A single element is allowed to exceed the maxweight to avoid deadlock. + Note that shutdown is only supported after there are no more put calls. + """ + def __init__( + self, + weighing_fn, # type: Callable[[Any], int] + maxsize=0, # type: int + maxweight=0, # type: int + ): + # type: (...) -> None + + """Initializes a ByteLimitedQueue. + + Args: + weighing_fn: A Callable that accepts an item and returns its integer + weight. + maxsize: The maximum number of items allowed in the queue. If 0 or + negative, there is no limit on the number of elements. + maxweight: The maximum accumulated weight allowed in the queue. + """ + super().__init__(maxsize=0) + self.max_elements = maxsize + self.max_weight = maxweight + self.weighing_fn = weighing_fn + self._byte_size = 0 + + def _is_full(self, item_size): + if self._qsize() == 0: + return False + if self.max_elements > 0 and self._qsize() >= self.max_elements: + return True + if self.max_weight > 0 and self._byte_size + item_size > self.max_weight: + return True + return False + + def put(self, item, block=True, timeout=None): Review Comment: It may be worth calling out in the docstring that we don't guarantee that the element will land as soon as enough space opens up, since https://github.com/python/cpython/blob/45c47d26c230086163ac1ef0aa9f955f794fb69c/Lib/queue.py#L214-L215 will wake up one random thread that is waiting, which might not be the one that can fit. this is fine as long as we are emptying the queue -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
