sven-weber-db commented on code in PR #55716: URL: https://github.com/apache/spark/pull/55716#discussion_r3280605465
########## python/pyspark/messages/spark_message_receiver.py: ########## @@ -0,0 +1,126 @@ +# +# 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. +# + +from enum import Enum +from functools import wraps +from typing import BinaryIO, Callable, TypeVar +from abc import ABC, abstractmethod + +from pyspark.messages.zero_copy_byte_stream import ZeroCopyByteStream + + +T = TypeVar("T", bound="SparkMessageReceiver") +R = TypeVar("R") + + +class MessageState(Enum): + WAITING_FOR_INIT = 1 + WAITING_FOR_DATA = 2 + WAITING_FOR_FINISH = 3 + DONE = 4 + + +class SparkMessageReceiver(ABC): + """ + Generic class that implements receiving messages from Spark. + Caution: This class is STATEFUL. It is expected, that the + methods of this class are called in the following order: + + 1. Init -> 2. Data stream -> 3. Finish + + This order is verified using assertions in the class. Each function + can be called EXACTLY ONCE in the specified order. + """ + + def __init__(self) -> None: + self._state = MessageState.WAITING_FOR_INIT + + @staticmethod + def _state_transition( + required_state: MessageState, next_state: MessageState + ) -> Callable[[Callable[[T], R]], Callable[[T], R]]: + """Decorator to enforce state transitions.""" + + def decorator(func: Callable[[T], R]) -> Callable[[T], R]: + @wraps(func) + def wrapper(self: T) -> R: + assert self._state == required_state + result = func(self) + self._state = next_state + return result + + return wrapper + + return decorator + + @_state_transition(MessageState.WAITING_FOR_INIT, MessageState.WAITING_FOR_DATA) + def get_init_message(self) -> ZeroCopyByteStream: + """ + Returns: + the binary contents of the initial message as a ZeroCopyByteStream. + """ + return self._do_get_init_message() + + @_state_transition(MessageState.WAITING_FOR_DATA, MessageState.WAITING_FOR_FINISH) + def get_data_stream(self) -> BinaryIO: + """ + Returns: + A binary stream containing the data to invoke the UDF on. + """ + return self._do_get_data_stream() + + @_state_transition(MessageState.WAITING_FOR_FINISH, MessageState.DONE) + def is_stream_finished(self) -> bool: Review Comment: I agree with your point. I didn't want to call it `get_` because, unlike the other functions, this one does not return any stream content. Instead, it returns whether the end of the stream could be successfully read. I renamed the function to `get_signal_signal_from_stream`. I think this captures both notions: 1. The function is a state transform - You would not expect that you can get the finish signal from the stream twice 2. The function does not return the actual stream content, but whether the finish signal was successfully received. Does this seem more reasonable to you? -- 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] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
