/**
* Copyright 2013 LiveRamp
*
* 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.liveramp.hank.util;
import com.liveramp.commons.collections.MemoryBoundLruHashMap;
import com.liveramp.commons.util.MemoryUsageEstimator;
public class SynchronizedMemoryBoundCacheExpiring<K, V> {
private final MemoryBoundLruHashMap<K, ValueAndTimestamp<V>> cache;
private final long expirationPeriodMs;
// A disabled cache will not add any synchronization overhead
public SynchronizedMemoryBoundCacheExpiring(boolean isEnabled,
long numBytesCapacity,
int numItemsCapacity,
long expirationPeriodSeconds,
MemoryUsageEstimator<K> keyEstimator,
MemoryUsageEstimator<V> valueEstimator) {
if (isEnabled) {
cache = new MemoryBoundLruHashMap<K, ValueAndTimestamp<V>>(
numItemsCapacity,
numBytesCapacity,
keyEstimator,
new ValueAndTimestampMemoryUsageEstimator<V>(valueEstimator));
} else {
cache = null;
}
this.expirationPeriodMs = expirationPeriodSeconds * 1000;
}
public boolean isEnabled() {
return cache != null;
}
public V get(K key) {
if (!isEnabled()) {
return null;
} else {
ValueAndTimestamp<V> cachedValue;
synchronized (cache) {
// Attempt to get from cache
cachedValue = cache.get(key);
// Expire if needed
if (cachedValue != null && shouldExpire(cachedValue)) {
cache.remove(key);
cachedValue = null;
}
}
if (cachedValue == null) {
return null;
} else {
return cachedValue.getValue();
}
}
}
public void put(K key, V value) {
if (isEnabled()) {
if (value == null) {
throw new IllegalArgumentException("Value to put in cache should not be null.");
}
synchronized (cache) {
cache.putAndEvict(key, new ValueAndTimestamp<V>(value, System.currentTimeMillis()));
}
}
}
public int size() {
if (!isEnabled()) {
return 0;
} else {
synchronized (cache) {
return cache.size();
}
}
}
public long getNumManagedBytes() {
if (!isEnabled()) {
return 0;
} else {
synchronized (cache) {
return cache.getNumManagedBytes();
}
}
}
protected boolean shouldExpire(ValueAndTimestamp<V> valueAndTimestamp) {
return (System.currentTimeMillis() - valueAndTimestamp.getTimestamp()) >= expirationPeriodMs;
}
private static class ValueAndTimestamp<V> {
private final V value;
private final long timestamp;
public ValueAndTimestamp(V value, long timestamp) {
this.value = value;
this.timestamp = timestamp;
}
public V getValue() {
return value;
}
public long getTimestamp() {
return timestamp;
}
}
private static class ValueAndTimestampMemoryUsageEstimator<T> implements MemoryUsageEstimator<ValueAndTimestamp<T>> {
MemoryUsageEstimator<T> valueEstimator;
public ValueAndTimestampMemoryUsageEstimator(MemoryUsageEstimator<T> valueEstimator) {
this.valueEstimator = valueEstimator;
}
@Override
public long estimateMemorySize(ValueAndTimestamp<T> item) {
return valueEstimator.estimateMemorySize(item.getValue());
}
}
}