#
# 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.
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"""
A PTransform that provides an unbounded, streaming source of empty byte arrays.
This can only be used with the flink runner.
"""
# pytype: skip-file
from __future__ import absolute_import
import json
from typing import Any
from typing import Dict
from apache_beam import PTransform
from apache_beam import Windowing
from apache_beam import pvalue
from apache_beam.transforms.window import GlobalWindows
[docs]class FlinkStreamingImpulseSource(PTransform):
URN = "flink:transform:streaming_impulse:v1"
config = {} # type: Dict[str, Any]
[docs] def expand(self, pbegin):
assert isinstance(pbegin, pvalue.PBegin), (
'Input to transform must be a PBegin but found %s' % pbegin)
return pvalue.PCollection(pbegin.pipeline, is_bounded=False)
[docs] def get_windowing(self, inputs):
return Windowing(GlobalWindows())
[docs] def infer_output_type(self, unused_input_type):
return bytes
[docs] def to_runner_api_parameter(self, context):
assert isinstance(self, FlinkStreamingImpulseSource), \
"expected instance of StreamingImpulseSource, but got %s" % self.__class__
return (self.URN, json.dumps(self.config))
[docs] def set_interval_ms(self, interval_ms):
"""Sets the interval (in milliseconds) between messages in the stream.
"""
self.config["interval_ms"] = interval_ms
return self
[docs] def set_message_count(self, message_count):
"""If non-zero, the stream will produce only this many total messages.
Otherwise produces an unbounded number of messages.
"""
self.config["message_count"] = message_count
return self
[docs] @staticmethod
@PTransform.register_urn("flink:transform:streaming_impulse:v1", None)
def from_runner_api_parameter(spec_parameter, _unused_context):
config = json.loads(spec_parameter)
instance = FlinkStreamingImpulseSource()
if "interval_ms" in config:
instance.set_interval_ms(config["interval_ms"])
if "message_count" in config:
instance.set_message_count(config["message_count"])
return instance