org.apache.activemq.store.SharedFileLocker Maven / Gradle / Ivy

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/**
 * 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.activemq.store;

import org.apache.activemq.broker.AbstractLocker;
import org.apache.activemq.util.LockFile;
import org.apache.activemq.util.ServiceStopper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.io.IOException;

/**
 * Represents an exclusive lock on a database to avoid multiple brokers running
 * against the same logical database.
 *
 * @org.apache.xbean.XBean element="shared-file-locker"
 *
 */
public class SharedFileLocker extends AbstractLocker {

    public static final File DEFAULT_DIRECTORY = new File("KahaDB");
    private static final Logger LOG = LoggerFactory.getLogger(SharedFileLocker.class);

    private LockFile lockFile;
    protected File directory = DEFAULT_DIRECTORY;

    @Override
    public void doStart() throws Exception {
        if (lockFile == null) {
            File lockFileName = new File(directory, "lock");
            lockFile = new LockFile(lockFileName, true);
            if (failIfLocked) {
                lockFile.lock();
            } else {
                boolean locked = false;
                while ((!isStopped()) && (!isStopping())) {
                    try {
                        lockFile.lock();
                        locked = keepAlive();
                        break;
                    } catch (IOException e) {
                        LOG.info("Database "
                                + lockFileName
                                + " is locked... waiting "
                                + (lockAcquireSleepInterval / 1000)
                                + " seconds for the database to be unlocked. Reason: "
                                + e);
                        try {
                            Thread.sleep(lockAcquireSleepInterval);
                        } catch (InterruptedException e1) {
                        }
                    }
                }
                if (!locked) {
                    throw new IOException("attempt to obtain lock aborted due to shutdown");
                }
            }
        }
    }

    @Override
    public boolean keepAlive() {
        return lockFile != null && lockFile.keepAlive();
    }

    @Override
    public void doStop(ServiceStopper stopper) throws Exception {
        lockFile.unlock();
        lockFile=null;
    }

    public File getDirectory() {
        return directory;
    }

    public void setDirectory(File directory) {
        this.directory = directory;
    }

    @Override
    public void configure(PersistenceAdapter persistenceAdapter) throws IOException {
        this.setDirectory(persistenceAdapter.getDirectory());
    }
}