| /** |
| * 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 org.apache.curator.utils.CloseableUtils; |
| 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 |
| { |
| CloseableUtils.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); |
| } |
| } |
| } |