| # |
| # 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. |
| # |
| |
| """Create transform for streaming.""" |
| |
| from __future__ import absolute_import |
| |
| from builtins import map |
| |
| from apache_beam import DoFn |
| from apache_beam import ParDo |
| from apache_beam import PTransform |
| from apache_beam import Windowing |
| from apache_beam import pvalue |
| from apache_beam.transforms.window import GlobalWindows |
| |
| |
| class StreamingCreate(PTransform): |
| """A specialized implementation for ``Create`` transform in streaming mode. |
| |
| Note: There is no unbounded source API in python to wrap the Create source, |
| so we map this to composite of Impulse primitive and an SDF. |
| """ |
| |
| def __init__(self, values, coder): |
| self.coder = coder |
| self.encoded_values = list(map(coder.encode, values)) |
| |
| class DecodeAndEmitDoFn(DoFn): |
| """A DoFn which stores encoded versions of elements. |
| |
| It also stores a Coder to decode and emit those elements. |
| TODO: BEAM-2422 - Make this a SplittableDoFn. |
| """ |
| |
| def __init__(self, encoded_values, coder): |
| self.encoded_values = encoded_values |
| self.coder = coder |
| |
| def process(self, unused_element): |
| for encoded_value in self.encoded_values: |
| yield self.coder.decode(encoded_value) |
| |
| class Impulse(PTransform): |
| """The Dataflow specific override for the impulse primitive.""" |
| |
| def expand(self, pbegin): |
| assert isinstance(pbegin, pvalue.PBegin), ( |
| 'Input to Impulse transform must be a PBegin but found %s' % pbegin) |
| return pvalue.PCollection(pbegin.pipeline, is_bounded=False) |
| |
| def get_windowing(self, inputs): |
| return Windowing(GlobalWindows()) |
| |
| def infer_output_type(self, unused_input_type): |
| return bytes |
| |
| def expand(self, pbegin): |
| return (pbegin |
| | 'Impulse' >> self.Impulse() |
| | 'Decode Values' >> ParDo( |
| self.DecodeAndEmitDoFn(self.encoded_values, self.coder))) |