001/**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.camel.util;
018
019import java.io.Serializable;
020import java.util.Collection;
021import java.util.Map;
022import java.util.Set;
023import java.util.concurrent.atomic.LongAdder;
024
025import com.github.benmanes.caffeine.cache.Cache;
026import com.github.benmanes.caffeine.cache.Caffeine;
027import com.github.benmanes.caffeine.cache.RemovalCause;
028import com.github.benmanes.caffeine.cache.RemovalListener;
029import org.slf4j.Logger;
030import org.slf4j.LoggerFactory;
031
032/**
033 * A cache that uses a near optional LRU Cache.
034 * <p/>
035 * The Cache is implemented by Caffeine which provides an <a href="https://github.com/ben-manes/caffeine/wiki/Efficiency">efficient cache</a>.
036 * <p/>
037 * If this cache stores {@link org.apache.camel.Service} then this implementation will on eviction
038 * invoke the {@link org.apache.camel.Service#stop()} method, to auto-stop the service.
039 * <p/>
040 * Use {@link LRUCacheFactory} to create a new instance (do not use the constructor).
041 *
042 * @see LRUCacheFactory
043 * @see LRUSoftCache
044 * @see LRUWeakCache
045 */
046public class LRUCache<K, V> implements Map<K, V>, RemovalListener<K, V>, Serializable {
047    private static final Logger LOG = LoggerFactory.getLogger(LRUCache.class);
048
049    protected final LongAdder hits = new LongAdder();
050    protected final LongAdder misses = new LongAdder();
051    protected final LongAdder evicted = new LongAdder();
052
053    private int maxCacheSize = 10000;
054    private boolean stopOnEviction;
055    private final Cache<K, V> cache;
056    private final Map<K, V> map;
057
058    /**
059     * Constructs an empty <tt>LRUCache</tt> instance with the
060     * specified maximumCacheSize, and will stop on eviction.
061     *
062     * @param maximumCacheSize the max capacity.
063     * @throws IllegalArgumentException if the initial capacity is negative
064     */
065    public LRUCache(int maximumCacheSize) {
066        this(16, maximumCacheSize); // 16 is the default initial capacity in ConcurrentLinkedHashMap
067    }
068
069    /**
070     * Constructs an empty <tt>LRUCache</tt> instance with the
071     * specified initial capacity, maximumCacheSize, and will stop on eviction.
072     *
073     * @param initialCapacity  the initial capacity.
074     * @param maximumCacheSize the max capacity.
075     * @throws IllegalArgumentException if the initial capacity is negative
076     */
077    public LRUCache(int initialCapacity, int maximumCacheSize) {
078        //Do not stop service if ConcurrentLinkedHashMap try to evict entry when its max capacity is zero.
079        this(initialCapacity, maximumCacheSize, maximumCacheSize > 0);
080    }
081
082    /**
083     * Constructs an empty <tt>LRUCache</tt> instance with the
084     * specified initial capacity, maximumCacheSize,load factor and ordering mode.
085     *
086     * @param initialCapacity  the initial capacity.
087     * @param maximumCacheSize the max capacity.
088     * @param stopOnEviction   whether to stop service on eviction.
089     * @throws IllegalArgumentException if the initial capacity is negative
090     */
091    public LRUCache(int initialCapacity, int maximumCacheSize, boolean stopOnEviction) {
092        this(initialCapacity, maximumCacheSize, stopOnEviction, false, false, false);
093    }
094
095    /**
096     * Constructs an empty <tt>LRUCache</tt> instance with the
097     * specified initial capacity, maximumCacheSize,load factor and ordering mode.
098     *
099     * @param initialCapacity  the initial capacity.
100     * @param maximumCacheSize the max capacity.
101     * @param stopOnEviction   whether to stop service on eviction.
102     * @param soft             whether to use soft values a soft cache  (default is false)
103     * @param weak             whether to use weak keys/values as a weak cache  (default is false)
104     * @param syncListener     whether to use synchronous call for the eviction listener (default is false)
105     * @throws IllegalArgumentException if the initial capacity is negative
106     */
107    public LRUCache(int initialCapacity, int maximumCacheSize, boolean stopOnEviction,
108                    boolean soft, boolean weak, boolean syncListener) {
109        Caffeine<K, V> caffeine = Caffeine.newBuilder()
110                .initialCapacity(initialCapacity)
111                .maximumSize(maximumCacheSize)
112                .removalListener(this);
113        if (soft) {
114            caffeine.softValues();
115        }
116        if (weak) {
117            caffeine.weakKeys();
118            caffeine.weakValues();
119        }
120        if (syncListener) {
121            caffeine.executor(Runnable::run);
122        }
123
124        this.cache = caffeine.build();
125        this.map = cache.asMap();
126        this.maxCacheSize = maximumCacheSize;
127        this.stopOnEviction = stopOnEviction;
128    }
129
130    @Override
131    public V get(Object o) {
132        V answer = map.get(o);
133        if (answer != null) {
134            hits.increment();
135        } else {
136            misses.increment();
137        }
138        return answer;
139    }
140
141    @Override
142    public int size() {
143        return map.size();
144    }
145
146    @Override
147    public boolean isEmpty() {
148        return map.isEmpty();
149    }
150
151    @Override
152    public boolean containsKey(Object o) {
153        return map.containsKey(o);
154    }
155
156    @Override
157    public boolean containsValue(Object o) {
158        return map.containsValue(0);
159    }
160
161    @Override
162    public V put(K k, V v) {
163        return map.put(k, v);
164    }
165
166    @Override
167    public V remove(Object o) {
168        return map.remove(o);
169    }
170
171    public void putAll(Map<? extends K, ? extends V> map) {
172        this.cache.putAll(map);
173    }
174
175    @Override
176    public void clear() {
177        map.clear();
178        resetStatistics();
179    }
180
181    @Override
182    public Set<K> keySet() {
183        return map.keySet();
184    }
185
186    @Override
187    public Collection<V> values() {
188        return map.values();
189    }
190
191    @Override
192    public Set<Entry<K, V>> entrySet() {
193        return map.entrySet();
194    }
195
196    @Override
197    public void onRemoval(K key, V value, RemovalCause cause) {
198        if (cause.wasEvicted()) {
199            evicted.increment();
200            LOG.trace("onRemoval {} -> {}", key, value);
201            if (stopOnEviction) {
202                try {
203                    // stop service as its evicted from cache
204                    ServiceHelper.stopService(value);
205                } catch (Exception e) {
206                    LOG.warn("Error stopping service: " + value + ". This exception will be ignored.", e);
207                }
208            }
209        }
210    }
211
212    /**
213     * Gets the number of cache hits
214     */
215    public long getHits() {
216        return hits.longValue();
217    }
218
219    /**
220     * Gets the number of cache misses.
221     */
222    public long getMisses() {
223        return misses.longValue();
224    }
225
226    /**
227     * Gets the number of evicted entries.
228     */
229    public long getEvicted() {
230        return evicted.longValue();
231    }
232
233    /**
234     * Returns the maxCacheSize.
235     */
236    public int getMaxCacheSize() {
237        return maxCacheSize;
238    }
239
240    /**
241     * Rest the cache statistics such as hits and misses.
242     */
243    public void resetStatistics() {
244        hits.reset();
245        misses.reset();
246        evicted.reset();
247    }
248
249    public void cleanUp() {
250        cache.cleanUp();
251    }
252
253    @Override
254    public String toString() {
255        return "LRUCache@" + ObjectHelper.getIdentityHashCode(this);
256    }
257}