| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| package org.apache.curator.framework.recipes.locks; |
| |
| import com.google.common.base.Preconditions; |
| import org.apache.curator.framework.CuratorFramework; |
| import java.util.concurrent.TimeUnit; |
| |
| /** |
| * A NON re-entrant mutex that works across JVMs. Uses Zookeeper to hold the lock. All processes in all JVMs that |
| * use the same lock path will achieve an inter-process critical section. |
| */ |
| public class InterProcessSemaphoreMutex implements InterProcessLock |
| { |
| private final InterProcessSemaphoreV2 semaphore; |
| private volatile Lease lease; |
| |
| /** |
| * @param client the client |
| * @param path path for the lock |
| */ |
| public InterProcessSemaphoreMutex(CuratorFramework client, String path) |
| { |
| this.semaphore = new InterProcessSemaphoreV2(client, path, 1); |
| } |
| |
| @Override |
| public void acquire() throws Exception |
| { |
| lease = semaphore.acquire(); |
| } |
| |
| @Override |
| public boolean acquire(long time, TimeUnit unit) throws Exception |
| { |
| Lease acquiredLease = semaphore.acquire(time, unit); |
| if ( acquiredLease == null ) |
| { |
| return false; // important - don't overwrite lease field if couldn't be acquired |
| } |
| lease = acquiredLease; |
| return true; |
| } |
| |
| @Override |
| public void release() throws Exception |
| { |
| Preconditions.checkState(lease != null, "Not acquired"); |
| |
| try |
| { |
| lease.close(); |
| } |
| finally |
| { |
| lease = null; |
| } |
| } |
| |
| @Override |
| public boolean isAcquiredInThisProcess() |
| { |
| return (lease != null); |
| } |
| } |