com.google.common.cache.CacheStats Maven / Gradle / Ivy
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/*
* Copyright (C) 2011 The Guava Authors
*
* 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.google.common.cache;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.math.LongMath.saturatedAdd;
import static com.google.common.math.LongMath.saturatedSubtract;
import com.google.common.annotations.GwtCompatible;
import com.google.common.base.MoreObjects;
import com.google.common.base.Objects;
import java.util.concurrent.Callable;
import javax.annotation.CheckForNull;
/**
* Statistics about the performance of a {@link Cache}. Instances of this class are immutable.
*
* Cache statistics are incremented according to the following rules:
*
*
* - When a cache lookup encounters an existing cache entry {@code hitCount} is incremented.
*
- When a cache lookup first encounters a missing cache entry, a new entry is loaded.
*
* - After successfully loading an entry {@code missCount} and {@code loadSuccessCount}
* are incremented, and the total loading time, in nanoseconds, is added to {@code
* totalLoadTime}.
*
- When an exception is thrown while loading an entry, {@code missCount} and {@code
* loadExceptionCount} are incremented, and the total loading time, in nanoseconds, is
* added to {@code 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 {@code
* missCount}.
*
* - When an entry is evicted from the cache, {@code evictionCount} is incremented.
*
- No stats are modified when a cache entry is invalidated or manually removed.
*
- No stats are modified by operations invoked on the {@linkplain Cache#asMap asMap} view of
* the cache.
*
*
* A lookup is specifically defined as an invocation of one of the methods {@link
* LoadingCache#get(Object)}, {@link LoadingCache#getUnchecked(Object)}, {@link Cache#get(Object,
* Callable)}, or {@link LoadingCache#getAll(Iterable)}.
*
* @author Charles Fry
* @since 10.0
*/
@GwtCompatible
@ElementTypesAreNonnullByDefault
public final class CacheStats {
private final long hitCount;
private final long missCount;
private final long loadSuccessCount;
private final long loadExceptionCount;
@SuppressWarnings("GoodTime") // should be a java.time.Duration
private final long totalLoadTime;
private final long evictionCount;
/**
* Constructs a new {@code CacheStats} instance.
*
*
Five 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.
*/
@SuppressWarnings("GoodTime") // should accept a java.time.Duration
public CacheStats(
long hitCount,
long missCount,
long loadSuccessCount,
long loadExceptionCount,
long totalLoadTime,
long evictionCount) {
checkArgument(hitCount >= 0);
checkArgument(missCount >= 0);
checkArgument(loadSuccessCount >= 0);
checkArgument(loadExceptionCount >= 0);
checkArgument(totalLoadTime >= 0);
checkArgument(evictionCount >= 0);
this.hitCount = hitCount;
this.missCount = missCount;
this.loadSuccessCount = loadSuccessCount;
this.loadExceptionCount = loadExceptionCount;
this.totalLoadTime = totalLoadTime;
this.evictionCount = evictionCount;
}
/**
* Returns the number of times {@link Cache} lookup methods have returned either a cached or
* uncached value. This is defined as {@code hitCount + missCount}.
*
*
Note: the values of the metrics are undefined in case of overflow (though it is
* guaranteed not to throw an exception). If you require specific handling, we recommend
* implementing your own stats collector.
*/
public long requestCount() {
return saturatedAdd(hitCount, missCount);
}
/** Returns the number of times {@link Cache} lookup methods have returned a cached value. */
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}.
*/
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.
*/
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 + loadExceptionCount}. Multiple concurrent misses for the same key will result
* in a single load operation.
*/
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 + loadExceptionCount}.
*
*
Note: the values of the metrics are undefined in case of overflow (though it is
* guaranteed not to throw an exception). If you require specific handling, we recommend
* implementing your own stats collector.
*/
public long loadCount() {
return saturatedAdd(loadSuccessCount, loadExceptionCount);
}
/**
* Returns the number of times {@link Cache} lookup methods have successfully loaded a new value.
* This is usually incremented in conjunction with {@link #missCount}, though {@code missCount} is
* also incremented when an exception is encountered during cache loading (see {@link
* #loadExceptionCount}). Multiple concurrent misses for the same key will result in a single load
* operation. This may be incremented not in conjunction with {@code missCount} if the load occurs
* as a result of a refresh or if the cache loader returned more items than was requested. {@code
* missCount} may also be incremented not in conjunction with this (nor {@link
* #loadExceptionCount}) on calls to {@code getIfPresent}.
*/
public long loadSuccessCount() {
return loadSuccessCount;
}
/**
* Returns the number of times {@link Cache} lookup methods threw an exception while loading a new
* value. This is usually 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. This may be incremented not in conjunction with {@code missCount} if the load occurs
* as a result of a refresh or if the cache loader returned more items than was requested. {@code
* missCount} may also be incremented not in conjunction with this (nor {@link #loadSuccessCount})
* on calls to {@code getIfPresent}.
*/
public long loadExceptionCount() {
return loadExceptionCount;
}
/**
* Returns the ratio of cache loading attempts which threw exceptions. This is defined as {@code
* loadExceptionCount / (loadSuccessCount + loadExceptionCount)}, or {@code 0.0} when {@code
* loadSuccessCount + loadExceptionCount == 0}.
*
*
Note: the values of the metrics are undefined in case of overflow (though it is
* guaranteed not to throw an exception). If you require specific handling, we recommend
* implementing your own stats collector.
*/
public double loadExceptionRate() {
long totalLoadCount = saturatedAdd(loadSuccessCount, loadExceptionCount);
return (totalLoadCount == 0) ? 0.0 : (double) loadExceptionCount / 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 loadExceptionCount} is incremented.
*/
@SuppressWarnings("GoodTime") // should return a java.time.Duration
public long totalLoadTime() {
return totalLoadTime;
}
/**
* Returns the average time spent loading new values. This is defined as {@code totalLoadTime /
* (loadSuccessCount + loadExceptionCount)}.
*
*
Note: the values of the metrics are undefined in case of overflow (though it is
* guaranteed not to throw an exception). If you require specific handling, we recommend
* implementing your own stats collector.
*/
public double averageLoadPenalty() {
long totalLoadCount = saturatedAdd(loadSuccessCount, loadExceptionCount);
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}.
*/
public long evictionCount() {
return evictionCount;
}
/**
* 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.
*/
public CacheStats minus(CacheStats other) {
return new CacheStats(
Math.max(0, saturatedSubtract(hitCount, other.hitCount)),
Math.max(0, saturatedSubtract(missCount, other.missCount)),
Math.max(0, saturatedSubtract(loadSuccessCount, other.loadSuccessCount)),
Math.max(0, saturatedSubtract(loadExceptionCount, other.loadExceptionCount)),
Math.max(0, saturatedSubtract(totalLoadTime, other.totalLoadTime)),
Math.max(0, saturatedSubtract(evictionCount, other.evictionCount)));
}
/**
* Returns a new {@code CacheStats} representing the sum of this {@code CacheStats} and {@code
* other}.
*
*
Note: the values of the metrics are undefined in case of overflow (though it is
* guaranteed not to throw an exception). If you require specific handling, we recommend
* implementing your own stats collector.
*
* @since 11.0
*/
public CacheStats plus(CacheStats other) {
return new CacheStats(
saturatedAdd(hitCount, other.hitCount),
saturatedAdd(missCount, other.missCount),
saturatedAdd(loadSuccessCount, other.loadSuccessCount),
saturatedAdd(loadExceptionCount, other.loadExceptionCount),
saturatedAdd(totalLoadTime, other.totalLoadTime),
saturatedAdd(evictionCount, other.evictionCount));
}
@Override
public int hashCode() {
return Objects.hashCode(
hitCount, missCount, loadSuccessCount, loadExceptionCount, totalLoadTime, evictionCount);
}
@Override
public boolean equals(@CheckForNull Object object) {
if (object instanceof CacheStats) {
CacheStats other = (CacheStats) object;
return hitCount == other.hitCount
&& missCount == other.missCount
&& loadSuccessCount == other.loadSuccessCount
&& loadExceptionCount == other.loadExceptionCount
&& totalLoadTime == other.totalLoadTime
&& evictionCount == other.evictionCount;
}
return false;
}
@Override
public String toString() {
return MoreObjects.toStringHelper(this)
.add("hitCount", hitCount)
.add("missCount", missCount)
.add("loadSuccessCount", loadSuccessCount)
.add("loadExceptionCount", loadExceptionCount)
.add("totalLoadTime", totalLoadTime)
.add("evictionCount", evictionCount)
.toString();
}
}