001    /**
002     * Copyright (c) 2010 Yahoo! Inc. All rights reserved.
003     * Licensed under the Apache License, Version 2.0 (the "License");
004     * you may not use this file except in compliance with the License.
005     * You may obtain a copy of the License at
006     *
007     *   http://www.apache.org/licenses/LICENSE-2.0
008     *
009     *  Unless required by applicable law or agreed to in writing, software
010     *  distributed under the License is distributed on an "AS IS" BASIS,
011     *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012     *  See the License for the specific language governing permissions and
013     *  limitations under the License. See accompanying LICENSE file.
014     */
015    package org.apache.oozie.service;
016    
017    /**
018     * A service is component managed by the {@link Services} singleton.
019     */
020    public interface Service {
021        public static final String DEFAULT_LOCK_TIMEOUT = "oozie.service.default.lock.timeout";
022    
023        /**
024         * Prefix for all services configuration properties.
025         */
026        public static final String CONF_PREFIX = "oozie.service.";
027    
028        /**
029         * Constant for XCommand
030         */
031        public static final String USE_XCOMMAND = "oozie.useXCommand";
032    
033        /**
034         * Initialize the service. <p/> Invoked by the {@link Service} singleton at start up time.
035         *
036         * @param services services singleton initializing the service.
037         * @throws ServiceException thrown if the service could not initialize.
038         */
039        public void init(Services services) throws ServiceException;
040    
041        /**
042         * Destroy the service. <p/> Invoked by the {@link Service} singleton at shutdown time.
043         */
044        public void destroy();
045    
046        /**
047         * Return the public interface of the service. <p/> Services are retrieved by its public interface. Specializations
048         * of services must return the public interface.
049         *
050         * @return the interface of the service.
051         */
052        public Class<? extends Service> getInterface();
053    
054        /**
055         * Lock timeout value if service is only allowed to have one single running instance.
056         */
057        public static long lockTimeout = Services.get().getConf().getLong(DEFAULT_LOCK_TIMEOUT, 5 * 1000);
058    
059    }