| #!/usr/bin/env python |
| # -*- encoding: utf-8 -*- |
| |
| # 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. |
| |
| '''stateful_component.py''' |
| from abc import abstractmethod |
| |
| class StatefulComponent(object): |
| """Defines a component that saves its internal state using the State interface |
| When running under effectively once semantics, the state is periodically checkpointed |
| and is replayed when errors occur to a globally consistent checkpoint. |
| """ |
| @abstractmethod |
| def init_state(self, state): |
| """Initializes the state of the function or operator to that of a previous checkpoint. |
| This method is invoked when a component is executed as part of a recovery run. In case |
| there was no prior state associated with the component, the state will be empty. |
| Stateful Spouts/Bolts are expected to hold on to the state variable to save their |
| internal state |
| Note that init_state() is called before initialize() |
| :param state: the previously saved state of the component. |
| """ |
| pass |
| |
| @abstractmethod |
| def pre_save(self): |
| """This is a hook for the component to perform some actions just before the |
| framework saves its state. |
| """ |
| pass |