/*
* Copyright (c) 2008-2013, Hazelcast, Inc. All Rights Reserved.
*
* Licensed 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 com.hazelcast.map;
import com.hazelcast.config.Config;
import com.hazelcast.config.InMemoryFormat;
import com.hazelcast.config.NearCacheConfig;
import com.hazelcast.monitor.impl.NearCacheStatsImpl;
import com.hazelcast.nio.serialization.Data;
import com.hazelcast.spi.NodeEngine;
import com.hazelcast.util.Clock;
import com.hazelcast.util.ExceptionUtil;
import java.util.Collections;
import java.util.Map;
import java.util.Set;
import java.util.TreeSet;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
/**
* NearCache.
*/
public class NearCache {
/**
* Used when caching nonexistent values.
*/
public static final Object NULL_OBJECT = new Object();
private static final int HUNDRED_PERCENT = 100;
private static final int EVICTION_PERCENTAGE = 20;
private static final int CLEANUP_INTERVAL = 5000;
private final int maxSize;
private volatile long lastCleanup;
private final long maxIdleMillis;
private final long timeToLiveMillis;
private final EvictionPolicy evictionPolicy;
private final InMemoryFormat inMemoryFormat;
private final MapService mapService;
private final NodeEngine nodeEngine;
private final AtomicBoolean canCleanUp;
private final AtomicBoolean canEvict;
private final ConcurrentMap<Data, CacheRecord> cache;
private final MapContainer mapContainer;
private final NearCacheStatsImpl nearCacheStats;
/**
* @param mapName
* @param mapService
*/
public NearCache(String mapName, MapService mapService) {
this.mapService = mapService;
this.nodeEngine = mapService.getNodeEngine();
this.mapContainer = mapService.getMapContainer(mapName);
Config config = nodeEngine.getConfig();
NearCacheConfig nearCacheConfig = config.findMapConfig(mapName).getNearCacheConfig();
maxSize = nearCacheConfig.getMaxSize() <= 0 ? Integer.MAX_VALUE : nearCacheConfig.getMaxSize();
maxIdleMillis = TimeUnit.SECONDS.toMillis(nearCacheConfig.getMaxIdleSeconds());
inMemoryFormat = nearCacheConfig.getInMemoryFormat();
timeToLiveMillis = TimeUnit.SECONDS.toMillis(nearCacheConfig.getTimeToLiveSeconds());
evictionPolicy = EvictionPolicy.valueOf(nearCacheConfig.getEvictionPolicy());
cache = new ConcurrentHashMap<Data, CacheRecord>();
canCleanUp = new AtomicBoolean(true);
canEvict = new AtomicBoolean(true);
nearCacheStats = new NearCacheStatsImpl();
lastCleanup = Clock.currentTimeMillis();
}
/**
* EvictionPolicy.
*/
static enum EvictionPolicy {
NONE, LRU, LFU
}
// this operation returns the given value in near-cache memory format (data or object)
public Object put(Data key, Data data) {
fireTtlCleanup();
if (evictionPolicy == EvictionPolicy.NONE && cache.size() >= maxSize) {
// no more space in near-cache -> return given value in near-cache format
if (data == null) {
return null;
} else {
return inMemoryFormat.equals(InMemoryFormat.OBJECT) ? mapService.toObject(data) : data;
}
}
if (evictionPolicy != EvictionPolicy.NONE && cache.size() >= maxSize) {
fireEvictCache();
}
final Object value;
if (data == null) {
value = NULL_OBJECT;
} else {
value = inMemoryFormat.equals(InMemoryFormat.OBJECT) ? mapService.toObject(data) : data;
}
final CacheRecord record = new CacheRecord(key, value);
cache.put(key, record);
updateSizeEstimator(calculateCost(record));
if (NULL_OBJECT.equals(value)) {
return null;
} else {
return value;
}
}
public NearCacheStatsImpl getNearCacheStats() {
return createNearCacheStats();
}
private NearCacheStatsImpl createNearCacheStats() {
long ownedEntryCount = 0;
long ownedEntryMemoryCost = 0;
for (CacheRecord record : cache.values()) {
ownedEntryCount++;
ownedEntryMemoryCost += record.getCost();
}
nearCacheStats.setOwnedEntryCount(ownedEntryCount);
nearCacheStats.setOwnedEntryMemoryCost(ownedEntryMemoryCost);
return nearCacheStats;
}
private void fireEvictCache() {
if (canEvict.compareAndSet(true, false)) {
try {
nodeEngine.getExecutionService().execute("hz:near-cache", new Runnable() {
public void run() {
try {
TreeSet<CacheRecord> records = new TreeSet<CacheRecord>(cache.values());
int evictSize = cache.size() * EVICTION_PERCENTAGE / HUNDRED_PERCENT;
int i = 0;
for (CacheRecord record : records) {
cache.remove(record.key);
updateSizeEstimator(-calculateCost(record));
if (++i > evictSize) {
break;
}
}
} finally {
canEvict.set(true);
}
}
});
} catch (RejectedExecutionException e) {
canEvict.set(true);
} catch (Exception e) {
throw ExceptionUtil.rethrow(e);
}
}
}
private void fireTtlCleanup() {
if (Clock.currentTimeMillis() < (lastCleanup + CLEANUP_INTERVAL)) {
return;
}
if (canCleanUp.compareAndSet(true, false)) {
try {
nodeEngine.getExecutionService().execute("hz:near-cache", new Runnable() {
public void run() {
try {
lastCleanup = Clock.currentTimeMillis();
for (Map.Entry<Data, CacheRecord> entry : cache.entrySet()) {
if (entry.getValue().expired()) {
final Data key = entry.getKey();
final CacheRecord record = cache.remove(key);
//if a mapping exists.
if (record != null) {
updateSizeEstimator(-calculateCost(record));
}
}
}
} finally {
canCleanUp.set(true);
}
}
});
} catch (RejectedExecutionException e) {
canCleanUp.set(true);
} catch (Exception e) {
throw ExceptionUtil.rethrow(e);
}
}
}
public Object get(Data key) {
fireTtlCleanup();
CacheRecord record = cache.get(key);
if (record != null) {
if (record.expired()) {
cache.remove(key);
updateSizeEstimator(-calculateCost(record));
nearCacheStats.incrementMisses();
return null;
}
record.access();
return record.value;
} else {
nearCacheStats.incrementMisses();
return null;
}
}
public void invalidate(Data key) {
final CacheRecord record = cache.remove(key);
// if a mapping exists for the key.
if (record != null) {
updateSizeEstimator(-calculateCost(record));
}
}
public void invalidate(Set<Data> keys) {
if (keys == null || keys.isEmpty()) {
return;
}
for (Data key : keys) {
invalidate(key);
}
}
public int size() {
return cache.size();
}
public void clear() {
cache.clear();
resetSizeEstimator();
}
public Map<Data, CacheRecord> getReadonlyMap() {
return Collections.unmodifiableMap(cache);
}
/**
* CacheRecord.
*/
public class CacheRecord implements Comparable<CacheRecord> {
final Data key;
final Object value;
final long creationTime;
final AtomicInteger hit;
volatile long lastAccessTime;
CacheRecord(Data key, Object value) {
this.key = key;
this.value = value;
long time = Clock.currentTimeMillis();
this.lastAccessTime = time;
this.creationTime = time;
this.hit = new AtomicInteger(0);
}
void access() {
hit.incrementAndGet();
nearCacheStats.incrementHits();
lastAccessTime = Clock.currentTimeMillis();
}
boolean expired() {
long time = Clock.currentTimeMillis();
return (maxIdleMillis > 0 && time > lastAccessTime + maxIdleMillis)
|| (timeToLiveMillis > 0 && time > creationTime + timeToLiveMillis);
}
public int compareTo(CacheRecord o) {
if (EvictionPolicy.LRU.equals(evictionPolicy)) {
return ((Long) this.lastAccessTime).compareTo((o.lastAccessTime));
} else if (EvictionPolicy.LFU.equals(evictionPolicy)) {
return ((Integer) this.hit.get()).compareTo((o.hit.get()));
}
return 0;
}
public boolean equals(Object o) {
if (o != null && o instanceof CacheRecord) {
return this.compareTo((CacheRecord) o) == 0;
}
return false;
}
// If you don't think instances of this class will ever be inserted into a HashMap/HashTable,
// the recommended hashCode implementation to use is:
public int hashCode() {
assert false : "hashCode not designed";
// any arbitrary constant will do.
return 42;
}
public long getCost() {
// todo find object size if not a Data instance.
if (!(value instanceof Data)) {
return 0;
}
final int numberOfLongs = 2;
final int numberOfIntegers = 3;
// value is Data
return key.getHeapCost()
+ ((Data) value).getHeapCost()
+ numberOfLongs * (Long.SIZE / Byte.SIZE)
// sizeof atomic integer
+ (Integer.SIZE / Byte.SIZE)
// object references (key, value, hit)
+ numberOfIntegers * (Integer.SIZE / Byte.SIZE);
}
public Data getKey() {
return key;
}
public Object getValue() {
return value;
}
}
private void resetSizeEstimator() {
mapContainer.getNearCacheSizeEstimator().reset();
}
private void updateSizeEstimator(long size) {
mapContainer.getNearCacheSizeEstimator().add(size);
}
private long calculateCost(CacheRecord record) {
return mapContainer.getNearCacheSizeEstimator().getCost(record);
}
}