/*
* Copyright 2014 Ben Manes. All Rights Reserved.
*
* Licensed 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 com.github.benmanes.caffeine.cache.stats;
import java.util.Objects;
import javax.annotation.Nonnegative;
import javax.annotation.Nonnull;
import javax.annotation.concurrent.Immutable;
import com.github.benmanes.caffeine.cache.Cache;
import com.github.benmanes.caffeine.cache.LoadingCache;
/**
* Statistics about the performance of a {@link Cache}.
* <p>
* Cache statistics are incremented according to the following rules:
* <ul>
* <li>When a cache lookup encounters an existing cache entry {@code hitCount} is incremented.
* <li>When a cache lookup first encounters a missing cache entry, a new entry is loaded.
* <ul>
* <li>After successfully loading an entry {@code missCount} and {@code loadSuccessCount} are
* incremented, and the total loading time, in nanoseconds, is added to
* {@code totalLoadTime}.
* <li>When an exception is thrown while loading an entry, {@code missCount} and {@code
* loadFailureCount} are incremented, and the total loading time, in nanoseconds, is
* added to {@code totalLoadTime}.
* <li>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 {@code missCount}.
* </ul>
* <li>When an entry is computed through the {@linkplain Cache#asMap asMap} the
* {@code loadSuccessCount} or {@code loadFailureCount} is incremented.
* <li>When an entry is evicted from the cache, {@code evictionCount} is incremented and the
* weight added to {@code evictionWeight}.
* <li>No stats are modified when a cache entry is invalidated or manually removed.
* <li>No stats are modified by non-computing operations invoked on the
* {@linkplain Cache#asMap asMap} view of the cache.
* </ul>
* <p>
* A lookup is specifically defined as an invocation of one of the methods
* {@link LoadingCache#get(Object)}, {@link Cache#get(Object, java.util.function.Function)}, or
* {@link LoadingCache#getAll(Iterable)}.
*
* @author ben.manes@gmail.com (Ben Manes)
*/
@Immutable
public final class CacheStats {
private static final CacheStats EMPTY_STATS = new CacheStats(0, 0, 0, 0, 0, 0, 0);
private final long hitCount;
private final long missCount;
private final long loadSuccessCount;
private final long loadFailureCount;
private final long totalLoadTime;
private final long evictionCount;
private final long evictionWeight;
/**
* Constructs a new {@code CacheStats} instance.
*
* @param hitCount the number of cache hits
* @param missCount the number of cache misses
* @param loadSuccessCount the number of successful cache loads
* @param loadFailureCount the number of failed cache loads
* @param totalLoadTime the total load time (success and failure)
* @param evictionCount the number of entries evicted from the cache
* @deprecated This constructor is scheduled for removal in version <tt>3.0.0</tt>.
*/
@Deprecated
public CacheStats(@Nonnegative long hitCount, @Nonnegative long missCount,
@Nonnegative long loadSuccessCount, @Nonnegative long loadFailureCount,
@Nonnegative long totalLoadTime, @Nonnegative long evictionCount) {
this(hitCount, missCount, loadSuccessCount, loadFailureCount, totalLoadTime, evictionCount, 0L);
}
/**
* Constructs a new {@code CacheStats} instance.
* <p>
* 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.
*
* @param hitCount the number of cache hits
* @param missCount the number of cache misses
* @param loadSuccessCount the number of successful cache loads
* @param loadFailureCount the number of failed cache loads
* @param totalLoadTime the total load time (success and failure)
* @param evictionCount the number of entries evicted from the cache
* @param evictionWeight the sum of weights of entries evicted from the cache
*/
public CacheStats(@Nonnegative long hitCount, @Nonnegative long missCount,
@Nonnegative long loadSuccessCount, @Nonnegative long loadFailureCount,
@Nonnegative long totalLoadTime, @Nonnegative long evictionCount,
@Nonnegative long evictionWeight) {
if ((hitCount < 0) || (missCount < 0) || (loadSuccessCount < 0) || (loadFailureCount < 0)
|| (totalLoadTime < 0) || (evictionCount < 0) || (evictionWeight < 0)) {
throw new IllegalArgumentException();
}
this.hitCount = hitCount;
this.missCount = missCount;
this.loadSuccessCount = loadSuccessCount;
this.loadFailureCount = loadFailureCount;
this.totalLoadTime = totalLoadTime;
this.evictionCount = evictionCount;
this.evictionWeight = evictionWeight;
}
/**
* Returns a statistics instance where no cache events have been recorded.
*
* @return an empty statistics instance
*/
@Nonnull
public static CacheStats empty() {
return EMPTY_STATS;
}
/**
* Returns the number of times {@link Cache} lookup methods have returned either a cached or
* uncached value. This is defined as {@code hitCount + missCount}.
*
* @return the {@code hitCount + missCount}
*/
@Nonnegative
public long requestCount() {
return hitCount + missCount;
}
/**
* Returns the number of times {@link Cache} lookup methods have returned a cached value.
*
* @return the number of times {@link Cache} lookup methods have returned a cached value
*/
@Nonnegative
public long hitCount() {
return hitCount;
}
/**
* Returns the ratio of cache requests which were hits. This is defined as
* {@code hitCount / requestCount}, or {@code 1.0} when {@code requestCount == 0}. Note that
* {@code hitRate + missRate =~ 1.0}.
*
* @return the ratio of cache requests which were hits
*/
@Nonnegative
public double hitRate() {
long requestCount = requestCount();
return (requestCount == 0) ? 1.0 : (double) hitCount / requestCount;
}
/**
* Returns the number of times {@link Cache} lookup methods have returned an uncached (newly
* loaded) value, or null. Multiple concurrent calls to {@link Cache} lookup methods on an absent
* value can result in multiple misses, all returning the results of a single cache load
* operation.
*
* @return the number of times {@link Cache} lookup methods have returned an uncached (newly
* loaded) value, or null
*/
@Nonnegative
public long missCount() {
return missCount;
}
/**
* Returns the ratio of cache requests which were misses. This is defined as
* {@code missCount / requestCount}, or {@code 0.0} when {@code requestCount == 0}.
* Note that {@code 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 {@code missCount >= loadSuccessCount + loadFailureCount}. Multiple
* concurrent misses for the same key will result in a single load operation.
*
* @return the ratio of cache requests which were misses
*/
@Nonnegative
public double missRate() {
long requestCount = requestCount();
return (requestCount == 0) ? 0.0 : (double) missCount / requestCount;
}
/**
* Returns the total number of times that {@link 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 {@code loadSuccessCount + loadFailureCount}.
*
* @return the {@code loadSuccessCount + loadFailureCount}
*/
@Nonnegative
public long loadCount() {
return loadSuccessCount + loadFailureCount;
}
/**
* Returns the number of times {@link Cache} lookup methods have successfully loaded a new value.
* This is always incremented in conjunction with {@link #missCount}, though {@code missCount}
* is also incremented when an exception is encountered during cache loading (see
* {@link #loadFailureCount}). Multiple concurrent misses for the same key will result in a
* single load operation.
*
* @return the number of times {@link Cache} lookup methods have successfully loaded a new value
*/
@Nonnegative
public long loadSuccessCount() {
return loadSuccessCount;
}
/**
* Returns the number of times {@link 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 {@code missCount}, though {@code missCount} is also incremented when cache
* loading completes successfully (see {@link #loadSuccessCount}). Multiple concurrent misses for
* the same key will result in a single load operation.
*
* @return the number of times {@link Cache} lookup methods failed to load a new value
*/
@Nonnegative
public long loadFailureCount() {
return loadFailureCount;
}
/**
* Returns the ratio of cache loading attempts which threw exceptions. This is defined as
* {@code loadFailureCount / (loadSuccessCount + loadFailureCount)}, or {@code 0.0} when
* {@code loadSuccessCount + loadFailureCount == 0}.
*
* @return the ratio of cache loading attempts which threw exceptions
*/
@Nonnegative
public double loadFailureRate() {
long totalLoadCount = loadSuccessCount + loadFailureCount;
return (totalLoadCount == 0)
? 0.0
: (double) loadFailureCount / totalLoadCount;
}
/**
* 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 {@code loadSuccessCount}
* or {@code loadFailureCount} is incremented.
*
* @return the total number of nanoseconds the cache has spent loading new values
*/
@Nonnegative
public long totalLoadTime() {
return totalLoadTime;
}
/**
* Returns the average time spent loading new values. This is defined as
* {@code totalLoadTime / (loadSuccessCount + loadFailureCount)}.
*
* @return the average time spent loading new values
*/
@Nonnegative
public double averageLoadPenalty() {
long totalLoadCount = loadSuccessCount + loadFailureCount;
return (totalLoadCount == 0)
? 0.0
: (double) totalLoadTime / totalLoadCount;
}
/**
* Returns the number of times an entry has been evicted. This count does not include manual
* {@linkplain Cache#invalidate invalidations}.
*
* @return the number of times an entry has been evicted
*/
@Nonnegative
public long evictionCount() {
return evictionCount;
}
/**
* Returns the sum of weights of evicted entries. This total does not include manual
* {@linkplain Cache#invalidate invalidations}.
*
* @return the sum of weights of evicted entities
*/
@Nonnegative
public long evictionWeight() {
return evictionWeight;
}
/**
* Returns a new {@code CacheStats} representing the difference between this {@code CacheStats}
* and {@code other}. Negative values, which aren't supported by {@code CacheStats} will be
* rounded up to zero.
*
* @param other the statistics to subtract with
* @return the difference between this instance and {@code other}
*/
@Nonnull
public CacheStats minus(@Nonnull CacheStats other) {
return new CacheStats(
Math.max(0L, hitCount - other.hitCount),
Math.max(0L, missCount - other.missCount),
Math.max(0L, loadSuccessCount - other.loadSuccessCount),
Math.max(0L, loadFailureCount - other.loadFailureCount),
Math.max(0L, totalLoadTime - other.totalLoadTime),
Math.max(0L, evictionCount - other.evictionCount),
Math.max(0L, evictionWeight - other.evictionWeight));
}
/**
* Returns a new {@code CacheStats} representing the sum of this {@code CacheStats} and
* {@code other}.
*
* @param other the statistics to add with
* @return the sum of the statistics
*/
@Nonnull
public CacheStats plus(@Nonnull CacheStats other) {
return new CacheStats(
hitCount + other.hitCount,
missCount + other.missCount,
loadSuccessCount + other.loadSuccessCount,
loadFailureCount + other.loadFailureCount,
totalLoadTime + other.totalLoadTime,
evictionCount + other.evictionCount,
evictionWeight + other.evictionWeight);
}
@Override
public int hashCode() {
return Objects.hash(hitCount, missCount, loadSuccessCount,
loadFailureCount, totalLoadTime, evictionCount, evictionWeight);
}
@Override
public boolean equals(Object o) {
if (o == this) {
return true;
} else if (!(o instanceof CacheStats)) {
return false;
}
CacheStats other = (CacheStats) o;
return hitCount == other.hitCount
&& missCount == other.missCount
&& loadSuccessCount == other.loadSuccessCount
&& loadFailureCount == other.loadFailureCount
&& totalLoadTime == other.totalLoadTime
&& evictionCount == other.evictionCount
&& evictionWeight == other.evictionWeight;
}
@Override
public String toString() {
return getClass().getSimpleName() + '{'
+ "hitCount=" + hitCount + ", "
+ "missCount=" + missCount + ", "
+ "loadSuccessCount=" + loadSuccessCount + ", "
+ "loadFailureCount=" + loadFailureCount + ", "
+ "totalLoadTime=" + totalLoadTime + ", "
+ "evictionCount=" + evictionCount + ", "
+ "evictionWeight=" + evictionWeight
+ '}';
}
}