/*
* JBoss, Home of Professional Open Source
* Copyright 2010 Red Hat Inc. and/or its affiliates and other
* contributors as indicated by the @author tags. All rights reserved.
* See the copyright.txt in the distribution for a full listing of
* individual contributors.
*
* This 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 2.1 of
* the License, or (at your option) any later version.
*
* This software 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
package org.infinispan.lucene.readlocks;
import org.infinispan.Cache;
import org.infinispan.lucene.InfinispanDirectory;
import org.infinispan.util.concurrent.ConcurrentMapFactory;
import java.util.concurrent.ConcurrentMap;
/**
* LocalLockMergingSegmentReadLocker decorates the {@link DistributedSegmentReadLocker} to minimize
* remote operations in case several IndexReaders are opened on the same {@link InfinispanDirectory}.
* It keeps track of locks which where already acquired for a specific filename from another request on
* the same node and merges the request so that the different clients share the same remote lock.
*
* @author Sanne Grinovero
* @since 4.1
*/
@SuppressWarnings("unchecked")
public class LocalLockMergingSegmentReadLocker implements SegmentReadLocker {
private final ConcurrentMap<String, LocalReadLock> localLocks = ConcurrentMapFactory.makeConcurrentMap();
private final DistributedSegmentReadLocker delegate;
/**
* Create a new LocalLockMergingSegmentReadLocker for specified cache and index name.
*
* @param cache
* @param indexName
*/
public LocalLockMergingSegmentReadLocker(Cache<?, ?> cache, String indexName) {
this.delegate = new DistributedSegmentReadLocker((Cache<Object, Integer>) cache, cache, cache, indexName);
}
/**
* Create a new LocalLockMergingSegmentReadLocker with special purpose caches
* @param locksCache the cache to be used to store distributed locks
* @param chunksCache the cache containing the chunks, this is where the bulk of data is stored
* @param metadataCache smaller cache for the metadata of stored elements
* @param indexName
*/
public LocalLockMergingSegmentReadLocker(Cache<?, ?> locksCache, Cache<?, ?> chunksCache, Cache<?, ?> metadataCache, String indexName) {
this.delegate = new DistributedSegmentReadLocker((Cache<Object, Integer>) locksCache, chunksCache, metadataCache, indexName);
}
/**
* {@inheritDoc}
*/
@Override
public boolean acquireReadLock(String name) {
LocalReadLock localReadLock = getLocalLockByName(name);
boolean acquired = localReadLock.acquire();
if (acquired) {
return true;
}
else {
// cleanup
localLocks.remove(name);
return false;
}
}
private LocalReadLock getLocalLockByName(String name) {
LocalReadLock localReadLock = localLocks.get(name);
if (localReadLock == null) {
LocalReadLock newReadLock = new LocalReadLock(name);
LocalReadLock prevReadLock = localLocks.putIfAbsent(name, newReadLock);
localReadLock = prevReadLock == null ? newReadLock : prevReadLock;
}
return localReadLock;
}
/**
* {@inheritDoc}
*/
@Override
public void deleteOrReleaseReadLock(String name) {
getLocalLockByName(name).release();
}
private class LocalReadLock {
private final String name;
private int value = 0;
LocalReadLock(String name) {
this.name = name;
}
/**
* @return true if the lock was acquired, false if it's too late: the file
* was deleted and this LocalReadLock should be removed too.
*/
synchronized boolean acquire() {
if (value == 0) {
boolean haveIt = delegate.acquireReadLock(name);
if (haveIt) {
value = 1;
return true;
} else {
value = -1;
return false;
}
} else if (value == -1) {
// it was deleted just a two lines ago
return false;
} else {
value++;
return true;
}
}
synchronized void release() {
value--;
if (value <= 0) {
localLocks.remove(name);
delegate.deleteOrReleaseReadLock(name);
}
}
}
}