| /** |
| * 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. |
| */ |
| |
| package org.apache.hadoop.yarn.service; |
| |
| import java.util.ArrayList; |
| import java.util.List; |
| |
| import org.apache.commons.logging.Log; |
| import org.apache.commons.logging.LogFactory; |
| import org.apache.hadoop.conf.Configuration; |
| |
| public abstract class AbstractService implements Service { |
| |
| private static final Log LOG = LogFactory.getLog(AbstractService.class); |
| |
| /** |
| * Service state: initially {@link STATE#NOTINITED}. |
| */ |
| private STATE state = STATE.NOTINITED; |
| |
| /** |
| * Service name. |
| */ |
| private final String name; |
| /** |
| * Service start time. Will be zero until the service is started. |
| */ |
| private long startTime; |
| |
| /** |
| * The configuration. Will be null until the service is initialized. |
| */ |
| private Configuration config; |
| |
| /** |
| * List of state change listeners; it is final to ensure |
| * that it will never be null. |
| */ |
| private List<ServiceStateChangeListener> listeners = |
| new ArrayList<ServiceStateChangeListener>(); |
| |
| /** |
| * Construct the service. |
| * @param name service name |
| */ |
| public AbstractService(String name) { |
| this.name = name; |
| } |
| |
| @Override |
| public synchronized STATE getServiceState() { |
| return state; |
| } |
| |
| /** |
| * {@inheritDoc} |
| * @throws IllegalStateException if the current service state does not permit |
| * this action |
| */ |
| @Override |
| public synchronized void init(Configuration conf) { |
| ensureCurrentState(STATE.NOTINITED); |
| this.config = conf; |
| changeState(STATE.INITED); |
| LOG.info("Service:" + getName() + " is inited."); |
| } |
| |
| /** |
| * {@inheritDoc} |
| * @throws IllegalStateException if the current service state does not permit |
| * this action |
| */ |
| @Override |
| public synchronized void start() { |
| startTime = System.currentTimeMillis(); |
| ensureCurrentState(STATE.INITED); |
| changeState(STATE.STARTED); |
| LOG.info("Service:" + getName() + " is started."); |
| } |
| |
| /** |
| * {@inheritDoc} |
| * @throws IllegalStateException if the current service state does not permit |
| * this action |
| */ |
| @Override |
| public synchronized void stop() { |
| if (state == STATE.STOPPED || |
| state == STATE.INITED || |
| state == STATE.NOTINITED) { |
| // already stopped, or else it was never |
| // started (eg another service failing canceled startup) |
| return; |
| } |
| ensureCurrentState(STATE.STARTED); |
| changeState(STATE.STOPPED); |
| LOG.info("Service:" + getName() + " is stopped."); |
| } |
| |
| @Override |
| public synchronized void register(ServiceStateChangeListener l) { |
| listeners.add(l); |
| } |
| |
| @Override |
| public synchronized void unregister(ServiceStateChangeListener l) { |
| listeners.remove(l); |
| } |
| |
| @Override |
| public String getName() { |
| return name; |
| } |
| |
| @Override |
| public synchronized Configuration getConfig() { |
| return config; |
| } |
| |
| @Override |
| public long getStartTime() { |
| return startTime; |
| } |
| |
| /** |
| * Verify that that a service is in a given state. |
| * @param currentState the desired state |
| * @throws IllegalStateException if the service state is different from |
| * the desired state |
| */ |
| private void ensureCurrentState(STATE currentState) { |
| ServiceOperations.ensureCurrentState(state, currentState); |
| } |
| |
| /** |
| * Change to a new state and notify all listeners. |
| * This is a private method that is only invoked from synchronized methods, |
| * which avoid having to clone the listener list. It does imply that |
| * the state change listener methods should be short lived, as they |
| * will delay the state transition. |
| * @param newState new service state |
| */ |
| private void changeState(STATE newState) { |
| state = newState; |
| //notify listeners |
| for (ServiceStateChangeListener l : listeners) { |
| l.stateChanged(this); |
| } |
| } |
| } |