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}