package org.apache.cassandra.cache;
/*
*
* 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.
*
*/
import java.util.concurrent.atomic.AtomicLong;
import com.reardencommerce.kernel.collections.shared.evictable.ConcurrentLinkedHashMap;
public class InstrumentedCache<K, V>
{
private int capacity;
private final ConcurrentLinkedHashMap<K, V> map;
private final AtomicLong requests = new AtomicLong(0);
private final AtomicLong hits = new AtomicLong(0);
private final AtomicLong lastRequests = new AtomicLong(0);
private final AtomicLong lastHits = new AtomicLong(0);
private volatile boolean capacitySetManually;
public InstrumentedCache(int capacity)
{
this.capacity = capacity;
map = ConcurrentLinkedHashMap.create(ConcurrentLinkedHashMap.EvictionPolicy.SECOND_CHANCE, capacity);
}
public void put(K key, V value)
{
map.put(key, value);
}
public V get(K key)
{
V v = map.get(key);
requests.incrementAndGet();
if (v != null)
hits.incrementAndGet();
return v;
}
public V getInternal(K key)
{
return map.get(key);
}
public void remove(K key)
{
map.remove(key);
}
public int getCapacity()
{
return capacity;
}
public boolean isCapacitySetManually()
{
return capacitySetManually;
}
public void updateCapacity(int capacity)
{
map.setCapacity(capacity);
this.capacity = capacity;
}
public void setCapacity(int capacity)
{
updateCapacity(capacity);
capacitySetManually = true;
}
public int getSize()
{
return map.size();
}
public long getHits()
{
return hits.get();
}
public long getRequests()
{
return requests.get();
}
public double getRecentHitRate()
{
long r = requests.get();
long h = hits.get();
try
{
return ((double)(h - lastHits.get())) / (r - lastRequests.get());
}
finally
{
lastRequests.set(r);
lastHits.set(h);
}
}
public void clear()
{
map.clear();
requests.set(0);
hits.set(0);
}
}