org.glassfish.hk2.utilities.cache.internal.WeakCARCacheImpl Maven / Gradle / Ivy
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package org.glassfish.hk2.utilities.cache.internal;
import java.util.Map;
import java.util.concurrent.atomic.AtomicLong;
import org.glassfish.hk2.utilities.cache.CacheKeyFilter;
import org.glassfish.hk2.utilities.cache.Computable;
import org.glassfish.hk2.utilities.cache.ComputationErrorException;
import org.glassfish.hk2.utilities.cache.WeakCARCache;
import org.glassfish.hk2.utilities.general.GeneralUtilities;
import org.glassfish.hk2.utilities.general.WeakHashClock;
import org.glassfish.hk2.utilities.general.WeakHashLRU;
/**
* Implements the CAR algorithm as found here:
*
* http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.105.6057
*
* @author jwells
*
*/
public class WeakCARCacheImpl implements WeakCARCache {
private final Computable computable;
private final int maxSize; // TODO, make this dynamic
private final WeakHashClock> t1;
private final WeakHashClock> t2;
private final WeakHashLRU b1;
private final WeakHashLRU b2;
// The target size of t1, adaptive
private int p = 0;
private final AtomicLong hits = new AtomicLong(0L);
private final AtomicLong tries = new AtomicLong(0L);
public WeakCARCacheImpl(Computable computable, int maxSize, boolean isWeak) {
this.computable = computable;
this.maxSize = maxSize;
t1 = GeneralUtilities.getWeakHashClock(isWeak);
t2 = GeneralUtilities.getWeakHashClock(isWeak);
b1 = GeneralUtilities.getWeakHashLRU(isWeak);
b2 = GeneralUtilities.getWeakHashLRU(isWeak);
}
private V getValueFromT(K key) {
CarValue cValue = t1.get(key);
if (cValue != null) {
// So fast
cValue.referenceBit = true;
return cValue.value;
}
cValue = t2.get(key);
if (cValue != null) {
// So fast
cValue.referenceBit = true;
return cValue.value;
}
return null;
}
/* (non-Javadoc)
* @see org.glassfish.hk2.utilities.cache.WeakCARCache#compute(java.lang.Object)
*/
@SuppressWarnings("unchecked")
@Override
public V compute(K key) {
tries.getAndIncrement();
V value = getValueFromT(key);
if (value != null) {
hits.getAndIncrement();
return value;
}
synchronized (this) {
value = getValueFromT(key);
if (value != null) {
hits.getAndIncrement();
return value;
}
// Cache Miss. First, get the value. Any failures
// will bubble up prior to us messing with any data structures
try {
value = computable.compute(key);
}
catch (ComputationErrorException cee) {
// In this case the value should not be kept in the cache
return (V) cee.getComputation();
}
int cacheSize = getValueSize();
if (cacheSize >= maxSize) {
replace();
boolean inB1 = b1.contains(key);
boolean inB2 = b2.contains(key);
if (!inB1 && !inB2) {
if ((t1.size() + b1.size()) >= maxSize) {
b1.remove();
}
else if ((t1.size() + t2.size() + b1.size() + b2.size()) >= (2 * maxSize)) {
b2.remove();
}
}
}
boolean inB1 = b1.contains(key);
boolean inB2 = b2.contains(key);
if (!inB1 && !inB2) {
t1.put(key, new CarValue(value));
}
else if (inB1) {
int b1size = b1.size();
if (b1size == 0) b1size = 1; // Can happen in a weak situation, we fake the one
int b2size = b2.size();
int ratio = b2size / b1size; // integer division
if (ratio <= 0) ratio = 1;
p = p + ratio;
if (p > maxSize) p = maxSize;
b1.remove(key);
t2.put(key, new CarValue(value));
}
else {
// Must be in B2
int b2size = b2.size();
if (b2size == 0) b2size = 1; // Can happen in a weak situation, we fake the one
int b1size = b1.size();
int ratio = b1size / b2size;
if (ratio <= 0) ratio = 1;
p = p - ratio;
if (p < 0) p = 0;
b2.remove(key);
t2.put(key, new CarValue(value));
}
}
return value;
}
private void replace() {
boolean found = false;
while (!found) {
int trySize = p;
if (trySize < 1) trySize = 1;
if (t1.size() >= trySize) {
Map.Entry> entry = t1.next();
if (entry.getValue().referenceBit == false) {
found = true;
t1.remove(entry.getKey());
b1.add(entry.getKey());
}
else {
CarValue entryValue = entry.getValue();
entryValue.referenceBit = false;
t1.remove(entry.getKey());
t2.put(entry.getKey(), entryValue);
}
}
else {
Map.Entry> entry = t2.next();
if (entry.getValue().referenceBit == false) {
found = true;
t2.remove(entry.getKey());
b2.add(entry.getKey());
}
else {
CarValue entryValue = entry.getValue();
entryValue.referenceBit = false;
}
}
}
}
/* (non-Javadoc)
* @see org.glassfish.hk2.utilities.cache.WeakCARCache#getKeySize()
*/
@Override
public synchronized int getKeySize() {
return t1.size() + t2.size() + b1.size() + b2.size();
}
/* (non-Javadoc)
* @see org.glassfish.hk2.utilities.cache.WeakCARCache#getValueSize()
*/
@Override
public synchronized int getValueSize() {
return t1.size() + t2.size();
}
/* (non-Javadoc)
* @see org.glassfish.hk2.utilities.cache.WeakCARCache#clear()
*/
@Override
public synchronized void clear() {
t1.clear();
t2.clear();
b1.clear();
b2.clear();
p = 0;
tries.set(0);
hits.set(0);
}
/* (non-Javadoc)
* @see org.glassfish.hk2.utilities.cache.WeakCARCache#getMaxSize()
*/
@Override
public int getMaxSize() {
return maxSize;
}
/* (non-Javadoc)
* @see org.glassfish.hk2.utilities.cache.WeakCARCache#getComputable()
*/
@Override
public Computable getComputable() {
return computable;
}
/* (non-Javadoc)
* @see org.glassfish.hk2.utilities.cache.WeakCARCache#remove(java.lang.Object)
*/
@Override
public synchronized boolean remove(K key) {
if (t1.remove(key) == null) {
if (t2.remove(key) == null) {
if (!b1.remove(key)) {
return b2.remove(key);
}
return true;
}
return true;
}
return true;
}
/* (non-Javadoc)
* @see org.glassfish.hk2.utilities.cache.WeakCARCache#releaseMatching(org.glassfish.hk2.utilities.cache.CacheKeyFilter)
*/
@Override
public synchronized void releaseMatching(CacheKeyFilter filter) {
if (filter == null) return;
b2.releaseMatching(filter);
b1.releaseMatching(filter);
t1.releaseMatching(filter);
t2.releaseMatching(filter);
}
/* (non-Javadoc)
* @see org.glassfish.hk2.utilities.cache.WeakCARCache#clearStaleReferences()
*/
@Override
public synchronized void clearStaleReferences() {
t1.clearStaleReferences();
t2.clearStaleReferences();
b1.clearStaleReferences();
b2.clearStaleReferences();
}
private static class CarValue {
private final V value;
private volatile boolean referenceBit = false;
private CarValue(V value) {
this.value = value;
}
}
/* (non-Javadoc)
* @see org.glassfish.hk2.utilities.cache.WeakCARCache#getT1Size()
*/
@Override
public int getT1Size() {
return t1.size();
}
/* (non-Javadoc)
* @see org.glassfish.hk2.utilities.cache.WeakCARCache#getT2Size()
*/
@Override
public int getT2Size() {
return t2.size();
}
/* (non-Javadoc)
* @see org.glassfish.hk2.utilities.cache.WeakCARCache#getB1Size()
*/
@Override
public int getB1Size() {
return b1.size();
}
/* (non-Javadoc)
* @see org.glassfish.hk2.utilities.cache.WeakCARCache#getB2Size()
*/
@Override
public int getB2Size() {
return b2.size();
}
/* (non-Javadoc)
* @see org.glassfish.hk2.utilities.cache.WeakCARCache#getP()
*/
@Override
public int getP() {
return p;
}
/* (non-Javadoc)
* @see org.glassfish.hk2.utilities.cache.WeakCARCache#dumpAllLists()
*/
@Override
public String dumpAllLists() {
StringBuffer sb = new StringBuffer("p=" + p + "\nT1: " + t1.toString() + "\n");
sb.append("T2: " + t2.toString() + "\n");
sb.append("B1: " + b1.toString() + "\n");
sb.append("B2: " + b2.toString() + "\n");
return sb.toString();
}
@Override
public double getHitRate() {
long localHits = hits.get();
long localTries = tries.get();
if (localTries == 0) localTries = 1;
return ((double) localHits / (double) localTries) * (double) 100.00;
}
@Override
public String toString() {
return "WeakCARCacheImpl(t1size=" + t1.size() + ",t2Size=" + t2.size() +
",b1Size=" + b1.size() + ",b2Size=" + b2.size() + ",p=" + p + "," +
"hitRate=" + getHitRate() + "%," + System.identityHashCode(this) + ")";
}
}
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