| package org.apache.helix.participant.statemachine; |
| |
| /* |
| * 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 org.apache.helix.NotificationContext; |
| import org.apache.helix.model.Message; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| public abstract class StateModel { |
| static final String DEFAULT_INITIAL_STATE = "OFFLINE"; |
| protected boolean _cancelled; |
| Logger logger = LoggerFactory.getLogger(StateModel.class); |
| |
| // TODO Get default state from implementation or from state model annotation |
| // StateModel with initial state other than OFFLINE should override this field |
| protected String _currentState = DEFAULT_INITIAL_STATE; |
| |
| public String getCurrentState() { |
| return _currentState; |
| } |
| |
| // @transition(from='from', to='to') |
| public void defaultTransitionHandler() { |
| logger |
| .error("Default default handler. The idea is to invoke this if no transition method is found. Yet to be implemented"); |
| } |
| |
| public boolean updateState(String newState) { |
| _currentState = newState; |
| return true; |
| } |
| |
| /** |
| * Called when error occurs in state transition |
| * TODO:enforce subclass to write this |
| * @param message |
| * @param context |
| * @param error |
| */ |
| public void rollbackOnError(Message message, NotificationContext context, |
| StateTransitionError error) { |
| |
| logger.error("Default rollback method invoked on error. Error Code: " + error.getCode()); |
| |
| } |
| |
| /** |
| * Called when the state model is reset |
| */ |
| public void reset() { |
| logger |
| .warn("Default reset method invoked. Either because the process longer own this resource or session timedout"); |
| } |
| |
| /** |
| * default transition for drop partition in error state |
| * @param message |
| * @param context |
| * @throws InterruptedException |
| */ |
| @Transition(to = "DROPPED", from = "ERROR") |
| public void onBecomeDroppedFromError(Message message, NotificationContext context) |
| throws Exception { |
| logger.info("Default ERROR->DROPPED transition invoked."); |
| } |
| |
| /** |
| * Default implementation for cancelling state transition |
| * |
| * IMPORTANT: |
| * |
| * 1. Be careful with the implementation of this method. There is no |
| * grantee that this method is called before user state transition method invoked. |
| * Please make sure the implemention contains logic for checking state transition already started. |
| * Similar to this situation, when this cancel method has been called. Helix does not grantee the |
| * state transition is still running. The state transition could be completed. |
| * |
| * 2. This cancel method should not throw HelixRollbackException. It is better to trigger the real |
| * state transition to throw HelixRollbackException if user would like to cancel the current |
| * running state transition. |
| */ |
| public void cancel() { |
| _cancelled = true; |
| } |
| |
| /** |
| * Default implementation to check whether state transition has been cancelled or not |
| * @return |
| */ |
| public boolean isCancelled() { |
| return _cancelled; |
| } |
| } |