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/*
* 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.geode.cache;
/**
* Defines common statistics information for both region and entries. All of these methods may throw
* a CacheClosedException, RegionDestroyedException or an EntryDestroyedException.
*
*
*
* @see Region#getStatistics
* @see Region.Entry#getStatistics
* @since GemFire 2.0
*/
public interface CacheStatistics {
/**
* For an entry, returns the time that the entry's value was last modified; for a region, the last
* time any of the region's entries' values or the values in subregions' entries were modified.
* The modification may have been initiated locally or it may have been an update distributed from
* another cache. It may also have been a new value provided by a loader. The modification time on
* a region is propagated upward to parent regions, transitively, to the root region.
*
* The number is expressed as the number of milliseconds since January 1, 1970. The granularity
* may be as course as 100ms, so the accuracy may be off by up to 50ms.
*
* Entry and subregion creation will update the modification time on a region, but
* destroy, destroyRegion, invalidate, and
* invalidateRegion do not update the modification time.
*
* @return the last modification time of the region or the entry; returns 0 if entry is invalid or
* modification time is uninitialized.
* @see Region#put(Object, Object)
* @see Region#get(Object)
* @see Region#create(Object, Object)
* @see Region#createSubregion
*/
public long getLastModifiedTime();
/**
* For an entry, returns the last time it was accessed via Region.get; for a region,
* the last time any of its entries or the entries of its subregions were accessed with
* Region.get. Any modifications will also update the lastAccessedTime, so
* lastAccessedTime is always >= lastModifiedTime. The
* lastAccessedTime on a region is propagated upward to parent regions, transitively,
* to the the root region.
*
* The number is expressed as the number of milliseconds since January 1, 1970. The granularity
* may be as course as 100ms, so the accuracy may be off by up to 50ms.
*
* @return the last access time of the region or the entry's value; returns 0 if entry is invalid
* or access time is uninitialized.
* @see Region#get(Object)
* @see #getLastModifiedTime
* @throws StatisticsDisabledException if statistics are not available
*/
public long getLastAccessedTime() throws StatisticsDisabledException;
/**
* Returns the number of times that {@link Region#get(Object) Region.get} on the region or the
* entry was called and there was no value found locally. Unlike lastAccessedTime,
* the miss count is not propagated to parent regions. Note that remote operations such as a "net
* search" do not effect the miss count.
*
* @return the number of cache misses on the region or the entry.
* @throws StatisticsDisabledException if statistics are not available
*/
public long getMissCount() throws StatisticsDisabledException;
/**
* Returns the number of hits for this region or entry. The number of hits is defined as the
* number of times when the {@link Region#get(Object) Region.get} finds a value locally. Unlike
* lastAccessedTime, the hit count is not propagated to parent regions. Note that
* remote operations such as a "net search" do not effect the hit count.
*
* @return the number of hits for this region or entry.
* @throws StatisticsDisabledException if statistics are not available
*/
public long getHitCount() throws StatisticsDisabledException;
/**
* Return the hit ratio, a convenience method defined as the ratio of hits to the number of calls
* to {@link Region#get(Object) Region.get}. If there have been zero calls to
* Region.get, then zero is returned.
*
* The hit ratio is equivalent to:
*
*
* long hitCount = getHitCount();
* long total = hitCount + getMissCount();
* return total == 0L ? 0.0f : ((float) hitCount / total);
*
*
* @throws StatisticsDisabledException if statistics are not available
* @return the hit ratio as a float
*/
public float getHitRatio() throws StatisticsDisabledException;
/**
* Reset the missCount and hitCount to zero for this entry.
*
* @throws StatisticsDisabledException if statistics are not available
*/
public void resetCounts() throws StatisticsDisabledException;
}