001 /**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements. See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership. The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License. You may obtain a copy of the License at
009 *
010 * http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019 package org.apache.hadoop.lib.server;
020
021 import org.apache.hadoop.classification.InterfaceAudience;
022
023 /**
024 * Service interface for components to be managed by the {@link Server} class.
025 */
026 @InterfaceAudience.Private
027 public interface Service {
028
029 /**
030 * Initializes the service. This method is called once, when the
031 * {@link Server} owning the service is being initialized.
032 *
033 * @param server the server initializing the service, give access to the
034 * server context.
035 *
036 * @throws ServiceException thrown if the service could not be initialized.
037 */
038 public void init(Server server) throws ServiceException;
039
040 /**
041 * Post initializes the service. This method is called by the
042 * {@link Server} after all services of the server have been initialized.
043 *
044 * @throws ServiceException thrown if the service could not be
045 * post-initialized.
046 */
047 public void postInit() throws ServiceException;
048
049 /**
050 * Destroy the services. This method is called once, when the
051 * {@link Server} owning the service is being destroyed.
052 */
053 public void destroy();
054
055 /**
056 * Returns the service dependencies of this service. The service will be
057 * instantiated only if all the service dependencies are already initialized.
058 *
059 * @return the service dependencies.
060 */
061 public Class[] getServiceDependencies();
062
063 /**
064 * Returns the interface implemented by this service. This interface is used
065 * the {@link Server} when the {@link Server#get(Class)} method is used to
066 * retrieve a service.
067 *
068 * @return the interface that identifies the service.
069 */
070 public Class getInterface();
071
072 /**
073 * Notification callback when the server changes its status.
074 *
075 * @param oldStatus old server status.
076 * @param newStatus new server status.
077 *
078 * @throws ServiceException thrown if the service could not process the status change.
079 */
080 public void serverStatusChange(Server.Status oldStatus, Server.Status newStatus) throws ServiceException;
081
082 }