/**
* 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.io.Closeables;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.state.ConnectionState;
import org.apache.curator.framework.state.ConnectionStateListener;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.apache.curator.test.Timing;
import java.io.Closeable;
import java.io.IOException;
import java.util.concurrent.Callable;
import java.util.concurrent.atomic.AtomicReference;
class SemaphoreClient implements Callable<Void>, ConnectionStateListener, Closeable
{
private final CuratorFramework client;
private final String semaphorePath;
private final Callable<Void> operation;
private volatile boolean shouldRun;
private volatile boolean hasAcquired;
private static final int CLIENT_EXCEPTION_HANDLER_SLEEP_TIME_SECS = 10;
private static final int MAX_SEMAPHORE_LEASES = 1;
private static final AtomicReference<SemaphoreClient> activeClient = new AtomicReference<SemaphoreClient>(null);
SemaphoreClient(String connectionString, String semaphorePath, Callable<Void> operation) throws IOException
{
Timing timing = new Timing();
this.client = CuratorFrameworkFactory.newClient(connectionString, timing.session(), timing.connection(), new ExponentialBackoffRetry(100, 3));
client.start();
this.semaphorePath = semaphorePath;
this.operation = operation;
}
@Override
public void close() throws IOException
{
shouldRun = false;
}
boolean hasAcquired()
{
return hasAcquired;
}
@Override
public void stateChanged(CuratorFramework client, ConnectionState newState)
{
hasAcquired = false;
}
static SemaphoreClient getActiveClient()
{
return activeClient.get();
}
@Override
public Void call() throws Exception
{
shouldRun = true;
client.getConnectionStateListenable().addListener(this);
try
{
while ( shouldRun )
{
try
{
acquireAndRun();
}
catch ( InterruptedException e )
{
Thread.currentThread().interrupt();
// propagate up, don't sleep
throw e;
}
catch ( Exception e )
{
Thread.sleep(CLIENT_EXCEPTION_HANDLER_SLEEP_TIME_SECS * 1000L);
}
}
}
catch ( InterruptedException e )
{
Thread.currentThread().interrupt();
}
finally
{
Closeables.closeQuietly(client);
}
return null;
}
private void acquireAndRun() throws Exception
{
InterProcessSemaphoreV2 semaphore = new InterProcessSemaphoreV2(client, semaphorePath, MAX_SEMAPHORE_LEASES);
Lease lease = semaphore.acquire();
try
{
hasAcquired = true;
if ( activeClient.compareAndSet(null, this) )
{
throw new Exception("Multiple acquirers");
}
try
{
while ( hasAcquired && shouldRun )
{
operation.call();
}
}
finally
{
if ( activeClient.compareAndSet(this, null) )
{
//noinspection ThrowFromFinallyBlock
throw new Exception("Bad release");
}
}
}
finally
{
semaphore.returnLease(lease);
}
}
}