DefaultCacheStats.java
/*
* Copyright (C) 2013-2024 The JavaParser Team.
*
* This file is part of JavaParser.
*
* JavaParser can be used either under the terms of
* a) the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
* b) the terms of the Apache License
*
* You should have received a copy of both licenses in LICENCE.LGPL and
* LICENCE.APACHE. Please refer to those files for details.
*
* JavaParser is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*/
package com.github.javaparser.symbolsolver.cache;
import static com.google.common.math.LongMath.saturatedAdd;
import static com.google.common.math.LongMath.saturatedSubtract;
import com.github.javaparser.resolution.cache.Cache;
import com.github.javaparser.resolution.cache.CacheStats;
import java.util.Arrays;
/**
* Statistics about the performance of a {@link Cache}. Instances of this class are immutable.
*
* <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
* loadExceptionCount} 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 evicted from the cache, {@code evictionCount} is incremented.
* <li>No stats are modified when a cache entry is invalidated or manually removed.
* <li>No stats are modified by operations invoked on the {@linkplain Cache#asMap asMap} view of
* the cache.
* </ul>
*
*/
public class DefaultCacheStats implements CacheStats {
private final long hitCount;
private final long missCount;
private final long loadSuccessCount;
private final long loadExceptionCount;
private final long totalLoadTime;
private final long evictionCount;
/**
* Constructs a new {@code ICacheStats} instance.
*
*/
public DefaultCacheStats() {
this.hitCount = 0;
this.missCount = 0;
this.loadSuccessCount = 0;
this.loadExceptionCount = 0;
this.totalLoadTime = 0;
this.evictionCount = 0;
}
/**
* Constructs a new {@code ICacheStats} instance.
*
*/
public DefaultCacheStats(
long hitCount,
long missCount,
long loadSuccessCount,
long loadExceptionCount,
long totalLoadTime,
long evictionCount) {
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}.
*
* <p><b>Note:</b> 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.
*/
@Override
public long requestCount() {
return saturatedAdd(hitCount, missCount);
}
/** Returns the number of times {@link Cache} lookup methods have returned a cached value. */
@Override
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}.
*/
@Override
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.
*/
@Override
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.
*/
@Override
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 and those that threw exceptions. This is
* defined as {@code loadSuccessCount + loadExceptionCount}.
*
* <p><b>Note:</b> 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.
*/
@Override
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}.
*/
@Override
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}.
*/
@Override
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}.
*
* <p><b>Note:</b> 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.
*/
@Override
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.
*/
@Override
@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)}.
*
* <p><b>Note:</b> 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.
*/
@Override
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}.
*/
@Override
public long evictionCount() {
return evictionCount;
}
/**
* Returns a new {@code ICacheStats} representing the difference between this {@code ICacheStats}
* and {@code other}. Negative values, which aren't supported by {@code ICacheStats} will be
* rounded up to zero.
*/
@Override
public CacheStats minus(CacheStats other) {
return new DefaultCacheStats(
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 ICacheStats} representing the sum of this {@code ICacheStats} and {@code
* other}.
*
* <p><b>Note:</b> 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
*/
@Override
public CacheStats plus(CacheStats other) {
return new DefaultCacheStats(
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 Arrays.hashCode(
new long[] {hitCount, missCount, loadSuccessCount, loadExceptionCount, totalLoadTime, evictionCount});
}
@Override
public boolean equals(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() {
StringBuilder sb = new StringBuilder(this.getClass().getSimpleName()).append(": ");
return sb.append("hitCount")
.append(hitCount)
.append(",")
.append("missCount")
.append(missCount)
.append(",")
.append("loadSuccessCount")
.append(loadSuccessCount)
.append(",")
.append("loadExceptionCount")
.append(loadExceptionCount)
.append(",")
.append("totalLoadTime")
.append(totalLoadTime)
.append(",")
.append("evictionCount")
.append(evictionCount)
.append(",")
.toString();
}
}