001/*
002 *  Copyright 2019 Anyware Services
003 *
004 *  Licensed under the Apache License, Version 2.0 (the "License");
005 *  you may not use this file except in compliance with the License.
006 *  You may obtain a copy of the License at
007 *
008 *      http://www.apache.org/licenses/LICENSE-2.0
009 *
010 *  Unless required by applicable law or agreed to in writing, software
011 *  distributed under the License is distributed on an "AS IS" BASIS,
012 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 *  See the License for the specific language governing permissions and
014 *  limitations under the License.
015 */
016package org.ametys.core.cache;
017
018/**
019 * CacheStats store hit, miss, and evictions of a cache.
020 * It can also compute rates, and compute the sum/difference between two CacheStats
021 */
022public interface CacheStats
023{
024
025    /**
026     * Returns the number of times cache lookup methods have returned either a cached or uncached value. 
027     * This is defined as hitCount + missCount.
028     * @return the number of times cache lookup methods have returned either a cached or uncached value.
029     */
030    public long requestCount();
031
032    /**
033     * Returns the number of times cache lookup methods have returned a cached value.
034     * @return the number of times cache lookup methods have returned a cached value.
035     */
036    public long hitCount();
037
038    /**
039     * Returns the ratio of cache requests which were hits. This is defined as hitCount/requestCount. If requestCount equals 0, return 1
040     * @return the ratio of cache requests which were hits.
041     */
042    public double hitRate();
043
044    /**
045     * Returns the number of times cache lookup methods have returned an uncached (newly loaded) value, or null.
046     * @return missCount
047     */
048    public long missCount();
049
050    /**
051     * Returns the ratio of cache requests which were misses. This is defined as
052     * missCount/requestCount. If requestCount equals 0, return 0
053     * @return the ratio of cache requests which were misses.
054     */
055    public double missRate();
056    
057    /**
058     * Returns the number of times an entry has been evicted. This count does not include manual invalidations.
059     * @return the number of times an entry has been evicted.
060     */
061    public long evictionCount();
062    
063    /**
064     * Returns the ratio of cache requests that lead to an eviction. This is defined as
065     * evictionCount/requestCount. If requestCount equals 0, return 0
066     * @return the ratio of cache requests that lead to an eviction.
067     */
068    public double evictionRate();
069
070    /**
071     * Returns a new CacheStats representing the difference between this CacheStats and other.
072     * @param cacheStats the other CacheStats
073     * @return the CacheStats representing the difference between this CacheStats and other.
074     */
075    public CacheStats minus(CacheStats cacheStats);
076    
077    /**
078     * Returns a new CacheStats representing the sum between this CacheStats and other
079     * @param cacheStats the other CacheStats
080     * @return the new CacheStats representing the sum between this CacheStats and other.
081     */
082    public CacheStats plus(CacheStats cacheStats);
083}