com.sun.appserv.util.cache.BoundedMultiLruCache Maven / Gradle / Ivy
/*
* Copyright (c) 1997, 2018 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0, which is available at
* http://www.eclipse.org/legal/epl-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception, which is available at
* https://www.gnu.org/software/classpath/license.html.
*
* SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
*/
package com.sun.appserv.util.cache;
import com.sun.enterprise.util.CULoggerInfo;
import java.text.MessageFormat;
import java.util.Properties;
import java.util.Map;
import java.util.Locale;
/**
* MultiLruCache -- in-memory bounded LRU cache with multiple LRU lists
* Underlying Hashtable is made into logical segments, with each segment
* having its own LRU list.
*/
public class BoundedMultiLruCache extends MultiLruCache {
// upper bound on the cache size
protected long maxSize = Constants.DEFAULT_MAX_CACHE_SIZE;
protected long currentSize;
private Object currentSizeLk = new Object();
/**
* initialize the LRU cache
* @param maxCapacity maximum number of entries this cache may hold
*/
public void init(int maxCapacity, Properties props) throws Exception {
super.init(maxCapacity, props);
currentSize = 0;
if (props != null) {
String strMaxSize = props.getProperty("MaxSize");
int multiplier = 1;
long size = -1;
String prop = strMaxSize;
if (prop != null) {
int index;
// upper case the string
prop = prop.toUpperCase(Locale.ENGLISH);
// look for 200KB or 80Kb or 1MB or 2Mb like suffixes
if ((index = prop.indexOf("KB")) != -1) {
multiplier = Constants.KB;
prop = prop.substring(0, index);
} else if ((index = prop.indexOf("MB")) != -1) {
multiplier = Constants.MB;
prop = prop.substring(0, index);
}
try {
size = Long.parseLong(prop.trim());
} catch (NumberFormatException nfe) {}
}
// sanity check and convert
if (size > 0)
maxSize = (size * multiplier);
else {
String msg = CULoggerInfo.getString(CULoggerInfo.boundedMultiLruCacheIllegalMaxSize);
Object[] params = { strMaxSize };
msg = MessageFormat.format(msg, params);
throw new IllegalArgumentException(msg);
}
}
}
/**
* this item is just added to the cache
* @param item CacheItem that was created
* @return a overflow item; may be null
*
* Cache bucket is already synchronized by the caller
*/
protected CacheItem itemAdded(CacheItem item) {
LruCacheItem overflow = (LruCacheItem) super.itemAdded(item);
// update the size
if (overflow != null) {
decrementCurrentSize(overflow.getSize());
}
incrementCurrentSize(item.getSize());
return overflow;
}
/**
* item value has been refreshed
* @param item CacheItem that was refreshed
* @param oldSize size of the previous value that was refreshed
* Cache bucket is already synchronized by the caller
*/
protected void itemRefreshed(CacheItem item, int oldSize) {
super.itemRefreshed(item, oldSize);
/** reduce the cache by the size of the size of the previous value
* and increment by the value being refreshed with.
*/
decrementCurrentSize(oldSize);
incrementCurrentSize(item.getSize());
}
/**
* item value has been removed from the cache
* @param item CacheItem that was just removed
*
* Cache bucket is already synchronized by the caller
*/
protected void itemRemoved(CacheItem item) {
super.itemRemoved(item);
// update the size
decrementCurrentSize(item.getSize());
}
/**
* has cache reached its threshold
* @return true when the cache reached its threshold
*/
protected boolean isThresholdReached() {
return (currentSize > maxSize || super.isThresholdReached());
}
/**
* synchronized counter updates
*/
protected final void incrementCurrentSize(int size) {
synchronized(currentSizeLk) {
currentSize += size;
}
}
protected final void decrementCurrentSize(int size) {
synchronized(currentSizeLk) {
currentSize -= size;
}
}
/**
* get generic stats from subclasses
*/
/**
* get the desired statistic counter
* @param key to corresponding stat
* @return an Object corresponding to the stat
* See also: Constant.java for the key
*/
public Object getStatByName(String key) {
Object stat = super.getStatByName(key);
if (stat == null && key != null) {
if (key.equals(Constants.STAT_BOUNDEDMULTILRUCACHE_CURRENT_SIZE))
stat = Long.valueOf(currentSize);
else if (key.equals(Constants.STAT_BOUNDEDMULTILRUCACHE_MAX_SIZE)) {
if (maxSize == Constants.DEFAULT_MAX_CACHE_SIZE)
stat = Constants.STAT_DEFAULT;
else
stat = Long.valueOf(maxSize);
}
}
return stat;
}
public Map getStats() {
Map stats = super.getStats();
// cache size in KB
stats.put(Constants.STAT_BOUNDEDMULTILRUCACHE_CURRENT_SIZE,
Long.valueOf(currentSize));
if (maxSize == Constants.DEFAULT_MAX_CACHE_SIZE) {
stats.put(Constants.STAT_BOUNDEDMULTILRUCACHE_MAX_SIZE,
Constants.STAT_DEFAULT);
}
else {
stats.put(Constants.STAT_BOUNDEDMULTILRUCACHE_MAX_SIZE,
Long.valueOf(maxSize));
}
return stats;
}
}