guava/src/com/google/common/cache/CacheStats.java - platform/external/guava - Git at Google

 /*
  * 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 com.google.common.annotations.Beta;
 import com.google.common.annotations.GwtCompatible;
 import com.google.common.base.Objects;

 import java.util.concurrent.Callable;

 import javax.annotation.Nullable;

 /**
  * 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 on a query to {@link Cache#getIfPresent}.
  * <li>No stats are modified by 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 LoadingCache#getUnchecked(Object)},
  * {@link Cache#get(Object, Callable)}, or {@link LoadingCache#getAll(Iterable)}.
  *
  * @author Charles Fry
  * @since 10.0
  */
 @Beta
 @GwtCompatible
 public final class 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 CacheStats} instance.
    *
    * <p>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.
    */
   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}.
    */
   public long requestCount() {
     return 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 &gt;= 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}.
    */
   public long loadCount() {
     return loadSuccessCount + loadExceptionCount;
   }

   /**
    * 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 #loadExceptionCount}). Multiple concurrent misses for the same key will result in a
    * single load operation.
    */
   public long loadSuccessCount() {
     return loadSuccessCount;
   }

   /**
    * Returns the number of times {@link Cache} lookup methods threw an exception while loading a
    * new value. 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.
    */
   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}.
    */
   public double loadExceptionRate() {
     long totalLoadCount = 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.
    */
   public long totalLoadTime() {
     return totalLoadTime;
   }

   /**
    * Returns the average time spent loading new values. This is defined as
    * {@code totalLoadTime / (loadSuccessCount + loadExceptionCount)}.
    */
   public double averageLoadPenalty() {
     long totalLoadCount = 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, hitCount - other.hitCount),
         Math.max(0, missCount - other.missCount),
         Math.max(0, loadSuccessCount - other.loadSuccessCount),
         Math.max(0, loadExceptionCount - other.loadExceptionCount),
         Math.max(0, totalLoadTime - other.totalLoadTime),
         Math.max(0, evictionCount - other.evictionCount));
   }

   /**
    * Returns a new {@code CacheStats} representing the sum of this {@code CacheStats}
    * and {@code other}.
    *
    * @since 11.0
    */
   public CacheStats plus(CacheStats other) {
     return new CacheStats(
         hitCount + other.hitCount,
         missCount + other.missCount,
         loadSuccessCount + other.loadSuccessCount,
         loadExceptionCount + other.loadExceptionCount,
         totalLoadTime + other.totalLoadTime,
         evictionCount + other.evictionCount);
   }

   @Override
   public int hashCode() {
     return Objects.hashCode(hitCount, missCount, loadSuccessCount, loadExceptionCount,
         totalLoadTime, evictionCount);
   }

   @Override
   public boolean equals(@Nullable 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 Objects.toStringHelper(this)
         .add("hitCount", hitCount)
         .add("missCount", missCount)
         .add("loadSuccessCount", loadSuccessCount)
         .add("loadExceptionCount", loadExceptionCount)
         .add("totalLoadTime", totalLoadTime)
         .add("evictionCount", evictionCount)
         .toString();
   }
 }
	/*
	* 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 com.google.common.annotations.Beta;
	import com.google.common.annotations.GwtCompatible;
	import com.google.common.base.Objects;

	import java.util.concurrent.Callable;

	import javax.annotation.Nullable;

	/**
	* 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 on a query to {@link Cache#getIfPresent}.
	* <li>No stats are modified by 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 LoadingCache#getUnchecked(Object)},
	* {@link Cache#get(Object, Callable)}, or {@link LoadingCache#getAll(Iterable)}.
	*
	* @author Charles Fry
	* @since 10.0
	*/
	@Beta
	@GwtCompatible
	public final class 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 CacheStats} instance.
	*
	* <p>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.
	*/
	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}.
	*/
	public long requestCount() {
	return 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}.
	*/
	public long loadCount() {
	return loadSuccessCount + loadExceptionCount;
	}

	/**
	* 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 #loadExceptionCount}). Multiple concurrent misses for the same key will result in a
	* single load operation.
	*/
	public long loadSuccessCount() {
	return loadSuccessCount;
	}

	/**
	* Returns the number of times {@link Cache} lookup methods threw an exception while loading a
	* new value. 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.
	*/
	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}.
	*/
	public double loadExceptionRate() {
	long totalLoadCount = 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.
	*/
	public long totalLoadTime() {
	return totalLoadTime;
	}

	/**
	* Returns the average time spent loading new values. This is defined as
	* {@code totalLoadTime / (loadSuccessCount + loadExceptionCount)}.
	*/
	public double averageLoadPenalty() {
	long totalLoadCount = 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, hitCount - other.hitCount),
	Math.max(0, missCount - other.missCount),
	Math.max(0, loadSuccessCount - other.loadSuccessCount),
	Math.max(0, loadExceptionCount - other.loadExceptionCount),
	Math.max(0, totalLoadTime - other.totalLoadTime),
	Math.max(0, evictionCount - other.evictionCount));
	}

	/**
	* Returns a new {@code CacheStats} representing the sum of this {@code CacheStats}
	* and {@code other}.
	*
	* @since 11.0
	*/
	public CacheStats plus(CacheStats other) {
	return new CacheStats(
	hitCount + other.hitCount,
	missCount + other.missCount,
	loadSuccessCount + other.loadSuccessCount,
	loadExceptionCount + other.loadExceptionCount,
	totalLoadTime + other.totalLoadTime,
	evictionCount + other.evictionCount);
	}

	@Override
	public int hashCode() {
	return Objects.hashCode(hitCount, missCount, loadSuccessCount, loadExceptionCount,
	totalLoadTime, evictionCount);
	}

	@Override
	public boolean equals(@Nullable 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 Objects.toStringHelper(this)
	.add("hitCount", hitCount)
	.add("missCount", missCount)
	.add("loadSuccessCount", loadSuccessCount)
	.add("loadExceptionCount", loadExceptionCount)
	.add("totalLoadTime", totalLoadTime)
	.add("evictionCount", evictionCount)
	.toString();
	}
	}