io.druid.server.lookup.cache.loading

Class LookupCacheStats

java.lang.Object

io.druid.server.lookup.cache.loading.LookupCacheStats

public class LookupCacheStats
extends Object

Statistics about the performance of a LoadingCache. Instances of this class are immutable. 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 missCount is incremented.
• When an entry is evicted from the cache, evictionCount is incremented.

Constructor Summary

Constructors

Constructor and Description
LookupCacheStats(long hitCount, long missCount, long evictionCount) Constructs a new CacheStats instance.

Method Summary

Modifier and Type	Method and Description
boolean	equals(Object o)
long	evictionCount() Returns the number of times an entry has been evicted.
int	hashCode()
long	hitCount() Returns the number of times LoadingCache lookup methods have returned a cached value.
double	hitRate() Returns the ratio of cache requests which were hits.
LookupCacheStats	minus(LookupCacheStats other) Returns a new CacheStats representing the difference between this CacheStats and other.
long	missCount() Returns the number of times LoadingCache lookup methods have returned an uncached (newly loaded) value, or null.
double	missRate() Returns the ratio of cache requests which were misses.
LookupCacheStats	plus(LookupCacheStats other) Returns a new CacheStats representing the sum of this CacheStats and other.
long	requestCount() Returns the number of times LoadingCache lookup methods have returned either a cached or uncached value.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

LookupCacheStats

public LookupCacheStats(long hitCount,
                        long missCount,
                        long evictionCount)

Constructs a new CacheStats instance.

Method Detail

requestCount

public long requestCount()

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

hitCount

public long hitCount()

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

hitRate

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.

missCount

public long missCount()

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

missRate

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 + loadExceptionCount. Multiple concurrent misses for the same key will result in a single load operation.

evictionCount

public long evictionCount()

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

minus

public LookupCacheStats minus(LookupCacheStats 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.

plus

public LookupCacheStats plus(LookupCacheStats other)

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

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object