Package com.github.benmanes.caffeine.cache.stats

Class CacheStats

  • @Immutable
public final class CacheStats
extends java.lang.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 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

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method 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​(java.lang.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.
      java.lang.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

    • Field Detail

      • EMPTY_STATS

        private static final CacheStats EMPTY_STATS

      • hitCount

        private final long hitCount

      • missCount

        private final long missCount

      • loadSuccessCount

        private final long loadSuccessCount

      • loadFailureCount

        private final long loadFailureCount

      • totalLoadTime

        private final long totalLoadTime

      • evictionCount

        private final long evictionCount

      • evictionWeight

        private final long evictionWeight

    • 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 java.lang.Object

      • equals

        public boolean equals​(java.lang.Object o)
        Overrides:
        equals in class java.lang.Object

      • toString

        public java.lang.String toString()
        Overrides:
        toString in class java.lang.Object