| # Copyright 2016 - Parsely, Inc. (d/b/a Parse.ly) |
| # |
| # Licensed 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. |
| '''transformoperator.py: API for defining generic transformer in python''' |
| from abc import abstractmethod |
| |
| class TransformOperator(object): |
| """API for defining a generic transformer for Heron in the Python Streamlet API |
| """ |
| |
| @abstractmethod |
| def setup(self, context): |
| """Called when a task for this operator is initialized within a worker on the cluster |
| |
| It provides the operator with the environment in which the bolt executes. |
| Note that ``__init__()`` should not be overriden for initialization of a bolt, as it is used |
| internally by BaseBolt; instead, ``initialize()`` should be used to initialize any custom |
| variables or connection to databases. |
| |
| :type context: :class:`Context` |
| :param context: This object can be used to get information about this task's place within the |
| topology, including the task id and component id of this task, input and output |
| information, etc. |
| **Must be implemented by a subclass, otherwise NotImplementedError is raised.** |
| """ |
| raise NotImplementedError("TransformOperator not implementing setup() method.") |
| |
| @abstractmethod |
| def transform(self, tup): |
| """Process a single tuple of input |
| |
| The Tuple object contains metadata on it about which component/stream/task it came from. |
| To emit a tuple, call ``context.emit(tuple)``. |
| |
| **Must be implemented by a subclass, otherwise NotImplementedError is raised.** |
| |
| :type tup: :class:`Tuple` |
| :param tup: Tuple to process |
| """ |
| raise NotImplementedError("TransformOperator not implementing transform() method.") |