001    /**
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.activemq.broker;
018    
019    import org.apache.activemq.Service;
020    import org.apache.activemq.store.PersistenceAdapter;
021    
022    import java.io.IOException;
023    
024    /**
025     * Represents a lock service to ensure that a broker is the only master
026     */
027    public interface Locker extends Service {
028    
029        /**
030         * Used by a timer to keep alive the lock.
031         * If the method returns false the broker should be terminated
032         * if an exception is thrown, the lock state cannot be determined
033         */
034        boolean keepAlive() throws IOException;
035    
036        /**
037         * set the delay interval in milliseconds between lock acquire attempts
038         *
039         * @param lockAcquireSleepInterval the sleep interval in miliseconds
040         */
041        void setLockAcquireSleepInterval(long lockAcquireSleepInterval);
042    
043        /**
044         * Set the name of the lock to use.
045         */
046        public void setName(String name);
047    
048        /**
049         * Specify whether to fail immediately if the lock is already held.  When set, the CustomLock must throw an
050         * IOException immediately upon detecting the lock is already held.
051         *
052         * @param failIfLocked: true => fail immediately if the lock is held; false => block until the lock can be obtained
053         *                      (default).
054         */
055        public void setFailIfLocked(boolean failIfLocked);
056    
057    
058        /**
059         * Optionally configure the locker with the persistence adapter currently used
060         * You can use persistence adapter configuration details like, data directory
061         * datasource, etc. to be used by the locker
062         *
063         * @param persistenceAdapter
064         * @throws IOException
065         */
066        public void configure(PersistenceAdapter persistenceAdapter) throws IOException;
067    
068    }