| /** |
| * 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. |
| */ |
| package org.apache.atlas.utils; |
| |
| import java.text.DateFormat; |
| import java.util.Date; |
| import java.util.LinkedHashMap; |
| import java.util.Map; |
| |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| /** |
| * Fixed size LRU Cache. |
| * |
| */ |
| public class LruCache<K, V> extends LinkedHashMap<K, V>{ |
| |
| private static final long serialVersionUID = 8715233786643882558L; |
| |
| private static final Logger LOGGER = LoggerFactory.getLogger(LruCache.class.getName()); |
| |
| /** |
| * Specifies the number evictions that pass before a warning is logged. |
| */ |
| private final int evictionWarningThrottle; |
| |
| // The number of evictions since the last warning was logged. |
| private long evictionsSinceWarning = 0; |
| |
| // When the last eviction warning was issued. |
| private Date lastEvictionWarning = new Date(); |
| |
| // The maximum number of entries the cache holds. |
| private final int capacity; |
| |
| |
| /** |
| * |
| * @param cacheSize The size of the cache. |
| * @param evictionWarningThrottle The number evictions that pass before a warning is logged. |
| */ |
| public LruCache(int cacheSize, int evictionWarningThrottle) { |
| super(cacheSize, 0.75f, true); |
| this.evictionWarningThrottle = evictionWarningThrottle; |
| this.capacity = cacheSize; |
| } |
| |
| @Override |
| protected boolean removeEldestEntry(Map.Entry<K,V> eldest) { |
| if( size() > capacity) { |
| evictionWarningIfNeeded(); |
| return true; |
| } |
| return false; |
| } |
| |
| /** |
| * Logs a warning if a threshold number of evictions has occurred since the |
| * last warning. |
| */ |
| private void evictionWarningIfNeeded() { |
| // If not logging eviction warnings, just return. |
| if (evictionWarningThrottle <= 0) { |
| return; |
| } |
| |
| evictionsSinceWarning++; |
| |
| if (evictionsSinceWarning >= evictionWarningThrottle) { |
| DateFormat dateFormat = DateFormat.getDateTimeInstance(); |
| if (LOGGER.isInfoEnabled()) { |
| LOGGER.info("There have been " + evictionsSinceWarning |
| + " evictions from the cache since " |
| + dateFormat.format(lastEvictionWarning)); |
| } |
| evictionsSinceWarning = 0; |
| lastEvictionWarning = new Date(); |
| } |
| } |
| |
| } |