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    import org.apache.oozie.util.Instrumentable;
018    import org.apache.oozie.util.Instrumentation;
019    import org.apache.oozie.util.MemoryLocks;
020    
021    public class MemoryLocksService implements Service, Instrumentable {
022        private static final String INSTRUMENTATION_GROUP = "locks";
023        private MemoryLocks locks;
024    
025        /**
026         * Initialize the memory locks service
027         *
028         * @param services services instance.
029         */
030        @Override
031        public void init(Services services) {
032            locks = new MemoryLocks();
033        }
034    
035        /**
036         * Destroy the memory locks service.
037         */
038        @Override
039        public void destroy() {
040            locks = null;
041        }
042    
043        /**
044         * Return the public interface for the memory locks services
045         *
046         * @return {@link MemoryLocksService}.
047         */
048        @Override
049        public Class<? extends Service> getInterface() {
050            return MemoryLocksService.class;
051        }
052    
053        /**
054         * Instruments the memory locks service.
055         *
056         * @param instr instance to instrument the memory locks service to.
057         */
058        public void instrument(Instrumentation instr) {
059            final MemoryLocks finalLocks = this.locks;
060            instr.addVariable(INSTRUMENTATION_GROUP, "locks", new Instrumentation.Variable<Long>() {
061                public Long getValue() {
062                    return (long) finalLocks.size();
063                }
064            });
065        }
066    
067        /**
068         * Obtain a READ lock for a source.
069         *
070         * @param resource resource name.
071         * @param wait time out in milliseconds to wait for the lock, -1 means no timeout and 0 no wait.
072         * @return the lock token for the resource, or <code>null</code> if the lock could not be obtained.
073         * @throws InterruptedException thrown if the thread was interrupted while waiting.
074         */
075        public MemoryLocks.LockToken getReadLock(String resource, long wait) throws InterruptedException {
076            return locks.getReadLock(resource, wait);
077        }
078    
079        /**
080         * Obtain a WRITE lock for a source.
081         *
082         * @param resource resource name.
083         * @param wait time out in milliseconds to wait for the lock, -1 means no timeout and 0 no wait.
084         * @return the lock token for the resource, or <code>null</code> if the lock could not be obtained.
085         * @throws InterruptedException thrown if the thread was interrupted while waiting.
086         */
087        public MemoryLocks.LockToken getWriteLock(String resource, long wait) throws InterruptedException {
088            return locks.getWriteLock(resource, wait);
089        }
090    
091    }