javax.cache
Interface CacheStatistics

All Known Subinterfaces:

CacheMXBean, CacheStatisticsMXBean

public interface CacheStatistics

Cache statistics.

Statistics are accumulated from the time a cache is created. They can be reset to zero using clearStatistics().

There are no defined consistency semantics for statistics. Refer to the implementation for precise semantics.

Since:

1.0

Author:

Greg Luck

Method Summary

void	clearStatistics() Clears the statistics counters to 0 for the associated Cache.
float	getAverageGetMillis() The mean time to execute gets.
float	getAveragePutMillis() The mean time to execute puts.
float	getAverageRemoveMillis() The mean time to execute removes.
long	getCacheEvictions() The total number of evictions from the cache.
long	getCacheGets() The total number of requests to the cache.
float	getCacheHitPercentage() This is a measure of cache efficiency.
long	getCacheHits() The number of get requests that were satisfied by the cache.
long	getCacheMisses() A miss is a get request which is not satisfied.
float	getCacheMissPercentage() Returns the percentage of cache accesses that did not find a requested entry in the cache.
long	getCachePuts() The total number of puts to the cache.
long	getCacheRemovals() The total number of removals from the cache.
Date	getStartAccumulationDate() The date from which statistics have been accumulated.

Method Detail

clearStatistics

void clearStatistics()

Clears the statistics counters to 0 for the associated Cache.

getStartAccumulationDate

Date getStartAccumulationDate()

The date from which statistics have been accumulated. Because statistics can be cleared, this is not necessarily since the cache was started.

Returns:

the date statistics started being accumulated

getCacheHits

long getCacheHits()

The number of get requests that were satisfied by the cache.

In a caches with multiple tiered storage, a hit may be implemented as a hit to the cache or to the first tier.

Returns:

the number of hits

getCacheHitPercentage

float getCacheHitPercentage()

This is a measure of cache efficiency. It is calculated as getCacheHits() divided by getCacheGets() * 100.

Returns:

the percentage of successful hits, as a decimal e.g 75.

getCacheMisses

long getCacheMisses()

A miss is a get request which is not satisfied.

In a simple cache a miss occurs when the cache does not satisfy the request.

In a caches with multiple tiered storage, a miss may be implemented as a miss to the cache or to the first tier.

In a read-through cache a miss is an absence of the key in the cache which will trigger a call to a CacheLoader. So it is still a miss even though the cache will load and return the value.

Refer to the implementation for precise semantics.

Returns:

the number of misses

getCacheMissPercentage

float getCacheMissPercentage()

Returns the percentage of cache accesses that did not find a requested entry in the cache. This is calculated as getCacheMisses() divided by getCacheGets() * 100.

Returns:

the percentage of accesses that failed to find anything

getCacheGets

long getCacheGets()

The total number of requests to the cache. This will be equal to the sum of the hits and misses.

A "get" is an operation that returns the current or previous value. It does not include checking for the existence of a key.

In a caches with multiple tiered storage, a gets may be implemented as a get to the cache or to the first tier.

Returns:

the number of gets

getCachePuts

long getCachePuts()

The total number of puts to the cache.

A put is counted even if it is immediately evicted. Replaces, where a put occurs which overrides an existing mapping is counted as a put.

Returns:

the number of hits

getCacheRemovals

long getCacheRemovals()

The total number of removals from the cache. This does not include evictions, where the cache itself initiates the removal to make space.

Returns:

the number of hits

getCacheEvictions

long getCacheEvictions()

The total number of evictions from the cache. An eviction is a removal initiated by the cache itself to free up space. An eviction is not treated as a removal and does not appear in the removal counts.

Returns:

the number of evictions from the cache

getAverageGetMillis

float getAverageGetMillis()

The mean time to execute gets.

In a read-through cache the time taken to load an entry on miss is not included in get time.

Returns:

the time in milliseconds

getAveragePutMillis

float getAveragePutMillis()

The mean time to execute puts.

Returns:

the time in milliseconds

getAverageRemoveMillis

float getAverageRemoveMillis()

The mean time to execute removes.

Returns:

the time in milliseconds