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MemoryLockProvider.java
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MemoryLockProvider.java
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/**
* This program is free software: you can redistribute it and/or modify it under the terms of the
* GNU Lesser General Public License as published by the Free Software Foundation, either version 3
* of the License, or (at your option) any later version.
*
* <p>This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
* without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* <p>You should have received a copy of the GNU Lesser General Public License along with this
* program. If not, see <http://www.gnu.org/licenses/>.
*
* <p>Copyright 2019
*/
package org.geowebcache.locks;
import java.util.concurrent.locks.ReentrantLock;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.apache.commons.codec.digest.DigestUtils;
import org.geotools.util.logging.Logging;
import org.geowebcache.GeoWebCacheException;
/**
* An in memory lock provider based on a striped lock
*
* @author Andrea Aime - GeoSolutions
*/
public class MemoryLockProvider implements LockProvider {
private static Logger LOGGER = Logging.getLogger(MemoryLockProvider.class.getName());
java.util.concurrent.locks.Lock[] locks;
public MemoryLockProvider() {
this(1024);
}
public MemoryLockProvider(int concurrency) {
locks = new java.util.concurrent.locks.Lock[concurrency];
for (int i = 0; i < locks.length; i++) {
locks[i] = new ReentrantLock();
}
}
@Override
public Lock getLock(String lockKey) {
final int idx = getIndex(lockKey);
if (LOGGER.isLoggable(Level.FINE))
LOGGER.fine("Mapped lock key " + lockKey + " to index " + idx + ". Acquiring lock.");
locks[idx].lock();
if (LOGGER.isLoggable(Level.FINE))
LOGGER.fine("Mapped lock key " + lockKey + " to index " + idx + ". Lock acquired");
return new Lock() {
boolean released = false;
@Override
public void release() throws GeoWebCacheException {
if (!released) {
released = true;
locks[idx].unlock();
if (LOGGER.isLoggable(Level.FINE))
LOGGER.fine("Released lock key " + lockKey + " mapped to index " + idx);
}
}
};
}
private int getIndex(String lockKey) {
// Simply hashing the lock key generated a significant number of collisions,
// doing the SHA1 digest of it provides a much better distribution
int idx = Math.abs(DigestUtils.sha1Hex(lockKey).hashCode() % locks.length);
return idx;
}
}