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.oozie.service;
020
021import org.apache.oozie.util.Instrumentable;
022import org.apache.oozie.util.Instrumentation;
023import org.apache.oozie.lock.LockToken;
024import org.apache.oozie.lock.MemoryLocks;
025
026/**
027 * Service that provides in-memory locks.  Assumes no other Oozie servers are using the database.
028 */
029public class MemoryLocksService implements Service, Instrumentable {
030    protected static final String INSTRUMENTATION_GROUP = "locks";
031    private MemoryLocks locks;
032
033    /**
034     * Initialize the memory locks service
035     *
036     * @param services services instance.
037     */
038    @Override
039    public void init(Services services) throws ServiceException {
040        locks = new MemoryLocks();
041    }
042
043    /**
044     * Destroy the memory locks service.
045     */
046    @Override
047    public void destroy() {
048        locks = null;
049    }
050
051    /**
052     * Return the public interface for the memory locks services
053     *
054     * @return {@link MemoryLocksService}.
055     */
056    @Override
057    public Class<? extends Service> getInterface() {
058        return MemoryLocksService.class;
059    }
060
061    /**
062     * Instruments the memory locks service.
063     *
064     * @param instr instance to instrument the memory locks service to.
065     */
066    public void instrument(Instrumentation instr) {
067        final MemoryLocks finalLocks = this.locks;
068        instr.addVariable(INSTRUMENTATION_GROUP, "locks", new Instrumentation.Variable<Long>() {
069            public Long getValue() {
070                return (long) finalLocks.size();
071            }
072        });
073    }
074
075    /**
076     * Obtain a READ lock for a source.
077     *
078     * @param resource resource name.
079     * @param wait time out in milliseconds to wait for the lock, -1 means no timeout and 0 no wait.
080     * @return the lock token for the resource, or <code>null</code> if the lock could not be obtained.
081     * @throws InterruptedException thrown if the thread was interrupted while waiting.
082     */
083    public LockToken getReadLock(String resource, long wait) throws InterruptedException {
084        return locks.getReadLock(resource, wait);
085    }
086
087    /**
088     * Obtain a WRITE lock for a source.
089     *
090     * @param resource resource name.
091     * @param wait time out in milliseconds to wait for the lock, -1 means no timeout and 0 no wait.
092     * @return the lock token for the resource, or <code>null</code> if the lock could not be obtained.
093     * @throws InterruptedException thrown if the thread was interrupted while waiting.
094     */
095    public LockToken getWriteLock(String resource, long wait) throws InterruptedException {
096        return locks.getWriteLock(resource, wait);
097    }
098}