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
019package org.apache.hadoop.lib.server;
020
021import org.apache.hadoop.classification.InterfaceAudience;
022
023/**
024 * Service interface for components to be managed by the {@link Server} class.
025 */
026@InterfaceAudience.Private
027public 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}