com.github.benmanes.caffeine.cache.stats

Class CacheStats

java.lang.Object

com.github.benmanes.caffeine.cache.stats.CacheStats

@Immutable
public final class CacheStats
extends Object

Statistics about the performance of a Cache.

Cache statistics are incremented according to the following rules:

• When a cache lookup encounters an existing cache entry hitCount is incremented.
• When a cache lookup first encounters a missing cache entry, a new entry is loaded.
  • After successfully loading an entry missCount and loadSuccessCount are incremented, and the total loading time, in nanoseconds, is added to totalLoadTime.
  • When an exception is thrown while loading an entry, missCount and loadFailureCount are incremented, and the total loading time, in nanoseconds, is added to totalLoadTime.
  • Cache lookups that encounter a missing cache entry that is still loading will wait for loading to complete (whether successful or not) and then increment missCount.
• When an entry is computed through the asMap the loadSuccessCount or loadFailureCount is incremented.
• When an entry is evicted from the cache, evictionCount is incremented and the weight added to evictionWeight.
• No stats are modified when a cache entry is invalidated or manually removed.
• No stats are modified by non-computing operations invoked on the asMap view of the cache.

A lookup is specifically defined as an invocation of one of the methods LoadingCache.get(Object), Cache.get(Object, java.util.function.Function), or LoadingCache.getAll(Iterable).

Constructor Summary

Constructors

Constructor and Description
CacheStats(long hitCount, long missCount, long loadSuccessCount, long loadFailureCount, long totalLoadTime, long evictionCount) Deprecated. This constructor is scheduled for removal in version 3.0.0.
CacheStats(long hitCount, long missCount, long loadSuccessCount, long loadFailureCount, long totalLoadTime, long evictionCount, long evictionWeight) Constructs a new CacheStats instance.

Method Summary

Modifier and Type	Method and Description
double	averageLoadPenalty() Returns the average time spent loading new values.
static CacheStats	empty() Returns a statistics instance where no cache events have been recorded.
boolean	equals(Object o)
long	evictionCount() Returns the number of times an entry has been evicted.
long	evictionWeight() Returns the sum of weights of evicted entries.
int	hashCode()
long	hitCount() Returns the number of times Cache lookup methods have returned a cached value.
double	hitRate() Returns the ratio of cache requests which were hits.
long	loadCount() Returns the total number of times that Cache lookup methods attempted to load new values.
long	loadFailureCount() Returns the number of times Cache lookup methods failed to load a new value, either because no value was found or an exception was thrown while loading.
double	loadFailureRate() Returns the ratio of cache loading attempts which threw exceptions.
long	loadSuccessCount() Returns the number of times Cache lookup methods have successfully loaded a new value.
CacheStats	minus(CacheStats other) Returns a new CacheStats representing the difference between this CacheStats and other.
long	missCount() Returns the number of times Cache lookup methods have returned an uncached (newly loaded) value, or null.
double	missRate() Returns the ratio of cache requests which were misses.
CacheStats	plus(CacheStats other) Returns a new CacheStats representing the sum of this CacheStats and other.
long	requestCount() Returns the number of times Cache lookup methods have returned either a cached or uncached value.
String	toString()
long	totalLoadTime() Returns the total number of nanoseconds the cache has spent loading new values.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

CacheStats

@Deprecated
public CacheStats(@Nonnegative
                              long hitCount,
                              @Nonnegative
                              long missCount,
                              @Nonnegative
                              long loadSuccessCount,
                              @Nonnegative
                              long loadFailureCount,
                              @Nonnegative
                              long totalLoadTime,
                              @Nonnegative
                              long evictionCount)

Deprecated. This constructor is scheduled for removal in version 3.0.0.

Constructs a new CacheStats instance.

Parameters:

hitCount - the number of cache hits

missCount - the number of cache misses

loadSuccessCount - the number of successful cache loads

loadFailureCount - the number of failed cache loads

totalLoadTime - the total load time (success and failure)

evictionCount - the number of entries evicted from the cache

CacheStats

public CacheStats(@Nonnegative
                  long hitCount,
                  @Nonnegative
                  long missCount,
                  @Nonnegative
                  long loadSuccessCount,
                  @Nonnegative
                  long loadFailureCount,
                  @Nonnegative
                  long totalLoadTime,
                  @Nonnegative
                  long evictionCount,
                  @Nonnegative
                  long evictionWeight)

Constructs a new CacheStats instance.

Many parameters of the same type in a row is a bad thing, but this class is not constructed by end users and is too fine-grained for a builder.

Parameters:

hitCount - the number of cache hits

missCount - the number of cache misses

loadSuccessCount - the number of successful cache loads

loadFailureCount - the number of failed cache loads

totalLoadTime - the total load time (success and failure)

evictionCount - the number of entries evicted from the cache

evictionWeight - the sum of weights of entries evicted from the cache

Method Detail

empty

@Nonnull
public static CacheStats empty()

Returns a statistics instance where no cache events have been recorded.

Returns:

an empty statistics instance

requestCount

@Nonnegative
public long requestCount()

Returns the number of times Cache lookup methods have returned either a cached or uncached value. This is defined as hitCount + missCount.

Returns:

the hitCount + missCount

hitCount

@Nonnegative
public long hitCount()

Returns the number of times Cache lookup methods have returned a cached value.

Returns:

the number of times Cache lookup methods have returned a cached value

hitRate

@Nonnegative
public double hitRate()

Returns the ratio of cache requests which were hits. This is defined as hitCount / requestCount, or 1.0 when requestCount == 0. Note that hitRate + missRate =~ 1.0.

Returns:

the ratio of cache requests which were hits

missCount

@Nonnegative
public long missCount()

Returns the number of times Cache lookup methods have returned an uncached (newly loaded) value, or null. Multiple concurrent calls to Cache lookup methods on an absent value can result in multiple misses, all returning the results of a single cache load operation.

Returns:

the number of times Cache lookup methods have returned an uncached (newly loaded) value, or null

missRate

@Nonnegative
public double missRate()

Returns the ratio of cache requests which were misses. This is defined as missCount / requestCount, or 0.0 when requestCount == 0. Note that hitRate + missRate =~ 1.0. Cache misses include all requests which weren't cache hits, including requests which resulted in either successful or failed loading attempts, and requests which waited for other threads to finish loading. It is thus the case that missCount >= loadSuccessCount + loadFailureCount. Multiple concurrent misses for the same key will result in a single load operation.

Returns:

the ratio of cache requests which were misses

loadCount

@Nonnegative
public long loadCount()

Returns the total number of times that Cache lookup methods attempted to load new values. This includes both successful load operations, as well as those that threw exceptions. This is defined as loadSuccessCount + loadFailureCount.

Returns:

the loadSuccessCount + loadFailureCount

loadSuccessCount

@Nonnegative
public long loadSuccessCount()

Returns the number of times Cache lookup methods have successfully loaded a new value. This is always incremented in conjunction with missCount, though missCount is also incremented when an exception is encountered during cache loading (see loadFailureCount). Multiple concurrent misses for the same key will result in a single load operation.

Returns:

the number of times Cache lookup methods have successfully loaded a new value

loadFailureCount

@Nonnegative
public long loadFailureCount()

Returns the number of times Cache lookup methods failed to load a new value, either because no value was found or an exception was thrown while loading. This is always incremented in conjunction with missCount, though missCount is also incremented when cache loading completes successfully (see loadSuccessCount). Multiple concurrent misses for the same key will result in a single load operation.

Returns:

the number of times Cache lookup methods failed to load a new value

loadFailureRate

@Nonnegative
public double loadFailureRate()

Returns the ratio of cache loading attempts which threw exceptions. This is defined as loadFailureCount / (loadSuccessCount + loadFailureCount), or 0.0 when loadSuccessCount + loadFailureCount == 0.

Returns:

the ratio of cache loading attempts which threw exceptions

totalLoadTime

@Nonnegative
public long totalLoadTime()

Returns the total number of nanoseconds the cache has spent loading new values. This can be used to calculate the miss penalty. This value is increased every time loadSuccessCount or loadFailureCount is incremented.

Returns:

the total number of nanoseconds the cache has spent loading new values

averageLoadPenalty

@Nonnegative
public double averageLoadPenalty()

Returns the average time spent loading new values. This is defined as totalLoadTime / (loadSuccessCount + loadFailureCount).

Returns:

the average time spent loading new values

evictionCount

@Nonnegative
public long evictionCount()

Returns the number of times an entry has been evicted. This count does not include manual invalidations.

Returns:

the number of times an entry has been evicted

evictionWeight

@Nonnegative
public long evictionWeight()

Returns the sum of weights of evicted entries. This total does not include manual invalidations.

Returns:

the sum of weights of evicted entities

minus

@Nonnull
public CacheStats minus(@Nonnull
                                 CacheStats other)

Returns a new CacheStats representing the difference between this CacheStats and other. Negative values, which aren't supported by CacheStats will be rounded up to zero.

Parameters:

other - the statistics to subtract with

Returns:

the difference between this instance and other

plus

@Nonnull
public CacheStats plus(@Nonnull
                                CacheStats other)

Returns a new CacheStats representing the sum of this CacheStats and other.

Parameters:

other - the statistics to add with

Returns:

the sum of the statistics

hashCode

public int hashCode()

Overrides:

hashCode in class Object

equals

public boolean equals(Object o)

Overrides:

equals in class Object

toString

public String toString()

Overrides:

toString in class Object