curator-examples/src/main/java/locking/ExampleClientThatLocks.java

/*
 * Copyright 2012 Netflix, Inc.
 *
 *    Licensed 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 locking;

import com.netflix.curator.framework.CuratorFramework;
import com.netflix.curator.framework.recipes.locks.InterProcessMutex;
import java.util.concurrent.TimeUnit;

public class ExampleClientThatLocks
{
    private final InterProcessMutex lock;
    private final FakeLimitedResource resource;
    private final String clientName;

    public ExampleClientThatLocks(CuratorFramework client, String lockPath, FakeLimitedResource resource, String clientName)
    {
        this.resource = resource;
        this.clientName = clientName;
        lock = new InterProcessMutex(client, lockPath);
    }

    public void     doWork(long time, TimeUnit unit) throws Exception
    {
        if ( !lock.acquire(time, unit) )
        {
            throw new IllegalStateException(clientName + " could not acquire the lock");
        }
        try
        {
            System.out.println(clientName + " has the lock");
            resource.use();
        }
        finally
        {
            System.out.println(clientName + " releasing the lock");
            lock.release(); // always release the lock in a finally block
        }
    }
}