[FLINK-38559][python] Support unordered mode of async function in Python DataStream API

flink-python/pyflink/datastream/__init__.py

@@ -256,6 +256,7 @@
     - :class:`OutputTag`:
       Tag with a name and type for identifying side output of an operator
 """
+from pyflink.datastream.async_data_stream import AsyncDataStream
 from pyflink.datastream.checkpoint_config import CheckpointConfig
 from pyflink.datastream.externalized_checkpoint_retention import ExternalizedCheckpointRetention
 from pyflink.datastream.checkpointing_mode import CheckpointingMode
@@ -268,7 +269,8 @@
                                           SinkFunction, CoProcessFunction, KeyedProcessFunction,
                                           KeyedCoProcessFunction, AggregateFunction, WindowFunction,
                                           ProcessWindowFunction, BroadcastProcessFunction,
-                                          KeyedBroadcastProcessFunction)
+                                          KeyedBroadcastProcessFunction, AsyncFunction,
+                                          ResultFuture)
 from pyflink.datastream.slot_sharing_group import SlotSharingGroup, MemorySize
 from pyflink.datastream.state_backend import (StateBackend, CustomStateBackend,
                                               PredefinedOptions, HashMapStateBackend,
@@ -292,6 +294,7 @@
     'ConnectedStreams',
     'BroadcastStream',
     'BroadcastConnectedStream',
+    'AsyncDataStream',
     'DataStreamSink',
     'MapFunction',
     'CoMapFunction',
@@ -308,6 +311,7 @@
     'AggregateFunction',
     'BroadcastProcessFunction',
     'KeyedBroadcastProcessFunction',
+    'AsyncFunction',
     'RuntimeContext',
     'TimerService',
     'CheckpointingMode',
@@ -338,5 +342,6 @@
     'SinkFunction',
     'SlotSharingGroup',
     'MemorySize',
-    'OutputTag'
+    'OutputTag',
+    'ResultFuture'
 ]

flink-python/pyflink/datastream/async_data_stream.py

@@ -0,0 +1,77 @@
+################################################################################
+#  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.
+################################################################################
+import inspect
+
+from pyflink.common import Time, TypeInformation
+from pyflink.datastream.data_stream import DataStream, _get_one_input_stream_operator
+from pyflink.datastream.functions import AsyncFunctionDescriptor, AsyncFunction
+from pyflink.java_gateway import get_gateway
+from pyflink.util.java_utils import get_j_env_configuration
+
+
+class AsyncDataStream(object):
+    """
+    A helper class to apply :class:`~AsyncFunction` to a data stream.
+    """
+
+    @staticmethod
+    def unordered_wait(
+            data_stream: DataStream,
+            async_function: AsyncFunction,
+            timeout: Time,
+            capacity: int = 100,
+            output_type: TypeInformation = None) -> 'DataStream':
+        """
+        Adds an async function to the data stream. The order of output stream records may be
+        reordered.
+
+        :param data_stream: The input data stream.
+        :param async_function: The async function.
+        :param timeout: The timeout for the asynchronous operation to complete.
+        :param capacity: The max number of async i/o operation that can be triggered.
+        :param output_type: The output data type.
+        :return: The transformed DataStream.
+        """
+        AsyncDataStream._validate(data_stream, async_function)
+
+        from pyflink.fn_execution import flink_fn_execution_pb2
+        j_python_data_stream_function_operator, j_output_type_info = \
+            _get_one_input_stream_operator(
+                data_stream,
+                AsyncFunctionDescriptor(
+                    async_function, timeout, capacity,
+                    AsyncFunctionDescriptor.OutputMode.UNORDERED),
+                flink_fn_execution_pb2.UserDefinedDataStreamFunction.PROCESS,  # type: ignore
+                output_type)
+        return DataStream(data_stream._j_data_stream.transform(
+            "async wait operator",
+            j_output_type_info,
+            j_python_data_stream_function_operator))
+
+    @staticmethod
+    def _validate(data_stream: DataStream, async_function: AsyncFunction):
+        if not inspect.iscoroutinefunction(async_function.async_invoke):
+            raise Exception("Method 'async_invoke' of class '%s' should be declared as 'async def'."
+                            % type(async_function))
+
+        gateway = get_gateway()
+        j_conf = get_j_env_configuration(data_stream._j_data_stream.getExecutionEnvironment())
+        python_execution_mode = (
+            j_conf.get(gateway.jvm.org.apache.flink.python.PythonOptions.PYTHON_EXECUTION_MODE))
+        if python_execution_mode == 'thread':
+            raise Exception("AsyncFunction is still not supported for 'thread' mode.")

flink-python/pyflink/datastream/data_stream.py

@@ -46,7 +46,8 @@
                                           KeyedBroadcastProcessFunction,
                                           InternalSingleValueAllWindowFunction,
                                           PassThroughAllWindowFunction,
-                                          InternalSingleValueProcessAllWindowFunction)
+                                          InternalSingleValueProcessAllWindowFunction,
+                                          AsyncFunctionDescriptor)
 from pyflink.datastream.output_tag import OutputTag
 from pyflink.datastream.slot_sharing_group import SlotSharingGroup
 from pyflink.datastream.state import (ListStateDescriptor, StateDescriptor, ReducingStateDescriptor,
@@ -2757,7 +2758,8 @@ def _is_keyed_stream(self):
 def _get_one_input_stream_operator(data_stream: DataStream,
                                    func: Union[Function,
                                                FunctionWrapper,
-                                               WindowOperationDescriptor],
+                                               WindowOperationDescriptor,
+                                               AsyncFunctionDescriptor],
                                    func_type: int,
                                    output_type: Union[TypeInformation, List] = None):
     """
@@ -2891,7 +2893,8 @@ def _get_two_input_stream_operator(connected_streams: ConnectedStreams,
 
 
 def _create_j_data_stream_python_function_info(
-    func: Union[Function, FunctionWrapper, WindowOperationDescriptor], func_type: int
+    func: Union[Function, FunctionWrapper, WindowOperationDescriptor, AsyncFunctionDescriptor],
+    func_type: int
 ) -> bytes:
     gateway = get_gateway()
 

flink-python/pyflink/datastream/functions.py

@@ -17,8 +17,10 @@
 ################################################################################
 
 from abc import ABC, abstractmethod
+from enum import Enum
+
 from py4j.java_gateway import JavaObject
-from typing import Union, Any, Generic, TypeVar, Iterable
+from typing import Union, Any, Generic, TypeVar, Iterable, List
 
 from pyflink.datastream.state import ValueState, ValueStateDescriptor, ListStateDescriptor, \
     ListState, MapStateDescriptor, MapState, ReducingStateDescriptor, ReducingState, \
@@ -53,6 +55,9 @@
     'BaseBroadcastProcessFunction',
     'BroadcastProcessFunction',
     'KeyedBroadcastProcessFunction',
+    'AsyncFunction',
+    'AsyncFunctionDescriptor',
+    'ResultFuture'
 ]
 
 
@@ -897,6 +902,83 @@ def on_timer(self, timestamp: int, ctx: 'KeyedCoProcessFunction.OnTimerContext')
         pass
 
 
+class ResultFuture(Generic[OUT]):
+    """
+    Collects data / error in user codes while processing async i/o.
+    """
+
+    @abstractmethod
+    def complete(self, result: List[OUT]):
+        """
+        Completes the result future with a collection of result objects.
+
+        Note that it should be called for exactly one time in the user code. Calling this function
+        for multiple times will cause data lose.
+
+        Put all results in a collection and then emit output.
+
+        :param result: A list of results.
+        """
+        pass
+
+    @abstractmethod
+    def complete_exceptionally(self, error: Exception):
+        """
+        Completes the result future exceptionally with an exception.
+
+        :param error: An Exception object.
+        """
+        pass
+
+
+class AsyncFunction(Function, Generic[IN, OUT]):
+    """
+    A function to trigger Async I/O operation.
+
+    For each #async_invoke, an async io operation can be triggered, and once it has been done, the
+    result can be collected by calling :func:`~ResultFuture.complete`. For each async operation, its
+    context is stored in the operator immediately after invoking #async_invoke, avoiding blocking
+    for each stream input as long as the internal buffer is not full.
+
+    :class:`~ResultFuture` can be passed into callbacks or futures to collect the result data. An
+    error can also be propagated to the async IO operator by
+    :func:`~ResultFuture.complete_exceptionally`.
+    """
+
+    @abstractmethod
+    async def async_invoke(self, value: IN, result_future: ResultFuture[OUT]):
+        """
+        Trigger async operation for each stream input.
+        In case of a user code error. You can raise an exception to make the task fail and
+        trigger fail-over process.
+
+        :param value: Input element coming from an upstream task.
+        :param result_future: A future to be completed with the result data.
+        """
+        pass
+
+    def timeout(self, value: IN, result_future: ResultFuture[OUT]):
+        """
+        In case :func:`~ResultFuture.async_invoke` timeout occurred. By default, the result future
+        is exceptionally completed with a timeout exception.
+        """
+        result_future.complete_exceptionally(
+            TimeoutError("Async function call has timed out for input: " + str(value)))
+
+
+class AsyncFunctionDescriptor(object):
+
+    class OutputMode(Enum):
+        ORDERED = 0
+        UNORDERED = 1
+
+    def __init__(self, async_function, timeout, capacity, output_mode):
+        self.async_function = async_function
+        self.timeout = timeout
+        self.capacity = capacity
+        self.output_mode = output_mode
+
+
 class WindowFunction(Function, Generic[IN, OUT, KEY, W]):
     """
     Base interface for functions that are evaluated over keyed (grouped) windows.