/*
* 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.jackrabbit.core.state;
import java.util.List;
import org.apache.commons.collections.map.LinkedMap;
import org.apache.jackrabbit.core.cache.CacheManager;
import org.apache.jackrabbit.core.cache.ConcurrentCache;
import org.apache.jackrabbit.core.id.ItemId;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* An <code>ItemStateCache</code> implementation that internally uses a
* {@link LinkedMap} to maintain a cache of <code>ItemState</code> objects. The
* cache uses a rough estimate of the memory consumption of the cached item
* states for calculating the maximum number of entries. The oldest entries
* are flushed once the cache size has exceeded a certain limit.
* <p>
* TODO rename class to something more appropriate, e.g. FIFOItemSateCache since
* it doesn't use a LRU eviction policy anymore.
*/
public class MLRUItemStateCache implements ItemStateCache {
/** Logger instance */
private static Logger log = LoggerFactory.getLogger(MLRUItemStateCache.class);
/** default maximum memory to use */
public static final int DEFAULT_MAX_MEM = 4 * 1024 * 1024;
/** the number of writes */
private volatile long numWrites = 0;
private final ConcurrentCache<ItemId, ItemState> cache =
new ConcurrentCache<ItemId, ItemState>(MLRUItemStateCache.class.getSimpleName());
public MLRUItemStateCache(CacheManager cacheMgr) {
cache.setMaxMemorySize(DEFAULT_MAX_MEM);
cache.setAccessListener(cacheMgr);
cacheMgr.add(cache);
}
//-------------------------------------------------------< ItemStateCache >
/**
* {@inheritDoc}
*/
public boolean isCached(ItemId id) {
return cache.containsKey(id);
}
/**
* {@inheritDoc}
*/
public ItemState retrieve(ItemId id) {
return cache.get(id);
}
/**
* {@inheritDoc}
*/
public ItemState[] retrieveAll() {
List<ItemState> values = cache.values();
return values.toArray(new ItemState[values.size()]);
}
/**
* {@inheritDoc}
*/
public void cache(ItemState state) {
cache.put(state.getId(), state, state.calculateMemoryFootprint());
if (numWrites++ % 10000 == 0 && log.isDebugEnabled()) {
log.debug("Item state cache size: {}% of {} bytes",
cache.getMemoryUsed() * 100 / cache.getMaxMemorySize(),
cache.getMaxMemorySize());
}
}
/**
* {@inheritDoc}
*/
public void evict(ItemId id) {
cache.remove(id);
}
/**
* {@inheritDoc}
*/
public void evictAll() {
cache.clear();
}
/**
* {@inheritDoc}
*/
public boolean isEmpty() {
return cache.isEmpty();
}
/**
* {@inheritDoc}
*/
public void dispose() {
cache.dispose();
}
}