WindowCacheStats.java

/*
 * Copyright (C) 2018, David Pursehouse <david.pursehouse@gmail.com> and others
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0 which is available at
 * https://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */
package org.eclipse.jgit.storage.file;

import java.util.Map;

import javax.management.MXBean;

import org.eclipse.jgit.internal.storage.file.WindowCache;

/**
 * Cache statistics for {@link WindowCache}.
 *
 * @since 4.11
 */
@MXBean
public interface WindowCacheStats {
    /**
     * @return the number of open files.
     * @deprecated use {@link #getOpenFileCount()} instead
     */
    @Deprecated
    public static int getOpenFiles() {
        return (int) WindowCache.getInstance().getStats().getOpenFileCount();
    }

    /**
     * @return the number of open bytes.
     * @deprecated use {@link #getOpenByteCount()} instead
     */
    @Deprecated
    public static long getOpenBytes() {
        return WindowCache.getInstance().getStats().getOpenByteCount();
    }

    /**
     * @return cache statistics for the WindowCache
     * @since 5.1.13
     */
    public static WindowCacheStats getStats() {
        return WindowCache.getInstance().getStats();
    }

    /**
     * Number of cache hits
     *
     * @return number of cache hits
     */
    long getHitCount();

    /**
     * Ratio of cache requests which were hits 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
     */
    default double getHitRatio() {
        long requestCount = getRequestCount();
        return (requestCount == 0) ? 1.0
                : (double) getHitCount() / requestCount;
    }

    /**
     * Number of cache misses.
     *
     * @return number of cash misses
     */
    long getMissCount();

    /**
     * Ratio of cache requests which were misses 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.
     *
     * @return the ratio of cache requests which were misses
     */
    default double getMissRatio() {
        long requestCount = getRequestCount();
        return (requestCount == 0) ? 0.0
                : (double) getMissCount() / requestCount;
    }

    /**
     * Number of successful loads
     *
     * @return number of successful loads
     */
    long getLoadSuccessCount();

    /**
     * Number of failed loads
     *
     * @return number of failed loads
     */
    long getLoadFailureCount();

    /**
     * Ratio of cache load 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
     */
    default double getLoadFailureRatio() {
        long loadFailureCount = getLoadFailureCount();
        long totalLoadCount = getLoadSuccessCount() + loadFailureCount;
        return (totalLoadCount == 0) ? 0.0
                : (double) loadFailureCount / totalLoadCount;
    }

    /**
     * Total number of times that the cache attempted to load new values. This
     * includes both successful load operations, as well as failed loads. This
     * is defined as {@code loadSuccessCount + loadFailureCount}.
     *
     * @return the {@code loadSuccessCount + loadFailureCount}
     */
    default long getLoadCount() {
        return getLoadSuccessCount() + getLoadFailureCount();
    }

    /**
     * Number of cache evictions
     *
     * @return number of evictions
     */
    long getEvictionCount();

    /**
     * Ratio of cache evictions. This is defined as
     * {@code evictionCount / requestCount}, or {@code 0.0} when
     * {@code requestCount == 0}.
     *
     * @return the ratio of cache loading attempts which threw exceptions
     */
    default double getEvictionRatio() {
        long evictionCount = getEvictionCount();
        long requestCount = getRequestCount();
        return (requestCount == 0) ? 0.0
                : (double) evictionCount / requestCount;
    }

    /**
     * Number of times the cache returned either a cached or uncached value.
     * This is defined as {@code hitCount + missCount}.
     *
     * @return the {@code hitCount + missCount}
     */
    default long getRequestCount() {
        return getHitCount() + getMissCount();
    }

    /**
     * Average time in nanoseconds for loading new values. This is
     * {@code totalLoadTime / (loadSuccessCount + loadFailureCount)}.
     *
     * @return the average time spent loading new values
     */
    default double getAverageLoadTime() {
        long totalLoadCount = getLoadSuccessCount() + getLoadFailureCount();
        return (totalLoadCount == 0) ? 0.0
                : (double) getTotalLoadTime() / totalLoadCount;
    }

    /**
     * Total time in nanoseconds the cache spent loading new values.
     *
     * @return the total number of nanoseconds the cache has spent loading new
     *         values
     */
    long getTotalLoadTime();

    /**
     * Number of pack files kept open by the cache
     *
     * @return number of files kept open by cache
     */
    long getOpenFileCount();

    /**
     * Number of bytes cached
     *
     * @return number of bytes cached
     */
    long getOpenByteCount();

    /**
     * Number of bytes cached per repository
     *
     * @return number of bytes cached per repository
     */
    Map<String, Long> getOpenByteCountPerRepository();

    /**
     * Reset counters. Does not reset open bytes and open files counters.
     */
    void resetCounters();
}