/*
 * Copyright (C) 2005-2014 Alfresco Software Limited.
 *
 * This file is part of Alfresco
 *
 * Alfresco is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Alfresco is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Alfresco. If not, see <http://www.gnu.org/licenses/>.
 */
package org.alfresco.repo.cache;

import org.alfresco.repo.cache.TransactionStats.OpType;

/**
 * Centralised cache statistics service. Transactional caches participating
 * in statistical collection will provide their data to this service using the
 * {@link #add(String, TransactionStats)} method. The data is then aggregated
 * so that, for example, the hit ratio for a particular cache may be retrieved.
 * 
 * @since 5.0
 * @author Matt Ward
 */
public interface CacheStatistics
{
    /**
     * Add new details to the system wide cache statistics.
     */
    void add(String cacheName, TransactionStats stats);
    
    /**
     * Get the number of occurrences of the given operation type,
     * retrieve the number of cache hits that have happened to the cache.
     * 
     * @param cacheName Name of the cache.
     * @param opType    Type of cache operation.
     * @return long count
     */
    long count(String cacheName, OpType opType);
    
    /**
     * The mean time in nanoseconds for all operations of the given type.
     * 
     * @param cacheName  The cache name.
     * @param opType     Type of operation, e.g. cache hits.
     * @return Time in nanos (double) or NaN if not available yet.
     */
    double meanTime(String cacheName, OpType opType);
    
    /**
     * The hit ratio for the given cache, where 1.0 is the maximum possible
     * value and 0.0 represents a cache that has never successfully
     * returned a previously cached value. 
     * 
     * @param cacheName  The cache name.
     * @return ratio (double)
     */
    double hitMissRatio(String cacheName); 
}