|
| 1 | +/* |
| 2 | + * Logback: the reliable, generic, fast and flexible logging framework. |
| 3 | + * Copyright (C) 1999-2025, QOS.ch. All rights reserved. |
| 4 | + * |
| 5 | + * This program and the accompanying materials are dual-licensed under |
| 6 | + * either the terms of the Eclipse Public License v1.0 as published by |
| 7 | + * the Eclipse Foundation |
| 8 | + * |
| 9 | + * or (per the licensee's choosing) |
| 10 | + * |
| 11 | + * under the terms of the GNU Lesser General Public License version 2.1 |
| 12 | + * as published by the Free Software Foundation. |
| 13 | + */ |
| 14 | + |
| 15 | +package ch.qos.logback.core.util; |
| 16 | + |
| 17 | +import java.util.concurrent.atomic.AtomicLong; |
| 18 | + |
| 19 | +/** |
| 20 | + * A simple time-based guard that limits the number of allowed operations within a sliding time window. |
| 21 | + * This class is useful for rate limiting or preventing excessive actions over time periods. |
| 22 | + * It supports time injection for testing purposes. |
| 23 | + * |
| 24 | + * @author Ceki Gülcü |
| 25 | + * @since 1.5.22 |
| 26 | + */ |
| 27 | +public class SimpleTimeBasedGuard { |
| 28 | + |
| 29 | + private final long windowDurationMs; |
| 30 | + private final int maxAllows; |
| 31 | + |
| 32 | + /** |
| 33 | + * Default window duration in milliseconds: 30 minutes. |
| 34 | + */ |
| 35 | + public static final long DEFAULT_WINDOW_MS = 30*60_000L; // 30 minutes |
| 36 | + |
| 37 | + /** |
| 38 | + * Default maximum number of allows per window: 2. |
| 39 | + */ |
| 40 | + public static final int DEFAULT_MAX_ALLOWS = 2; |
| 41 | + |
| 42 | + // Injectable time |
| 43 | + private final AtomicLong artificialTime = new AtomicLong(-1L); |
| 44 | + |
| 45 | + // Current window state |
| 46 | + private volatile long windowStartMs = 0; |
| 47 | + private volatile int allowsUsed = 0; |
| 48 | + |
| 49 | + /** |
| 50 | + * Creates a guard with custom limits. |
| 51 | + * |
| 52 | + * @param windowDurationMs how many millis per window (e.g. 30_000 for 30 minutes) |
| 53 | + * @param maxAllows how many allows per window (e.g. 2) |
| 54 | + */ |
| 55 | + public SimpleTimeBasedGuard(long windowDurationMs, int maxAllows) { |
| 56 | + if (windowDurationMs <= 0) throw new IllegalArgumentException("windowDurationMs must be > 0"); |
| 57 | + if (maxAllows < 1) throw new IllegalArgumentException("maxAllows must be >= 1"); |
| 58 | + |
| 59 | + this.windowDurationMs = windowDurationMs; |
| 60 | + this.maxAllows = maxAllows; |
| 61 | + } |
| 62 | + |
| 63 | + /** |
| 64 | + * Convenience: uses defaults — 2 allows every 30 minutes |
| 65 | + */ |
| 66 | + public SimpleTimeBasedGuard() { |
| 67 | + this(DEFAULT_WINDOW_MS, DEFAULT_MAX_ALLOWS); |
| 68 | + } |
| 69 | + |
| 70 | + /** |
| 71 | + * Checks if an operation is allowed based on the current time window. |
| 72 | + * If allowed, increments the usage count for the current window. |
| 73 | + * If the window has expired, resets the window and allows the operation. |
| 74 | + * |
| 75 | + * @return true if the operation is allowed, false otherwise |
| 76 | + */ |
| 77 | + public synchronized boolean allow() { |
| 78 | + long now = currentTimeMillis(); |
| 79 | + |
| 80 | + // First call ever |
| 81 | + if (windowStartMs == 0) { |
| 82 | + windowStartMs = now; |
| 83 | + allowsUsed = 1; |
| 84 | + return true; |
| 85 | + } |
| 86 | + |
| 87 | + // Still in current window? |
| 88 | + if (now < windowStartMs + windowDurationMs) { |
| 89 | + if (allowsUsed < maxAllows) { |
| 90 | + allowsUsed++; |
| 91 | + return true; |
| 92 | + } |
| 93 | + return false; |
| 94 | + } |
| 95 | + |
| 96 | + // New window → reset |
| 97 | + windowStartMs = now; |
| 98 | + allowsUsed = 1; |
| 99 | + return true; |
| 100 | + } |
| 101 | + |
| 102 | + // --- Time injection for testing --- |
| 103 | + |
| 104 | + /** |
| 105 | + * Sets the artificial current time for testing purposes. |
| 106 | + * When set, {@link #currentTimeMillis()} will return this value instead of {@link System#currentTimeMillis()}. |
| 107 | + * |
| 108 | + * @param timestamp the artificial timestamp in milliseconds |
| 109 | + */ |
| 110 | + public void setCurrentTimeMillis(long timestamp) { |
| 111 | + this.artificialTime.set(timestamp); |
| 112 | + } |
| 113 | + |
| 114 | + /** |
| 115 | + * Clears the artificial time, reverting to using {@link System#currentTimeMillis()}. |
| 116 | + */ |
| 117 | + public void clearCurrentTime() { |
| 118 | + this.artificialTime.set(-1L); |
| 119 | + } |
| 120 | + |
| 121 | + private long currentTimeMillis() { |
| 122 | + long t = artificialTime.get(); |
| 123 | + return t >= 0 ? t : System.currentTimeMillis(); |
| 124 | + } |
| 125 | + |
| 126 | + void incCurrentTimeMillis(long increment) { |
| 127 | + artificialTime.getAndAdd(increment); |
| 128 | + } |
| 129 | + |
| 130 | + // --- Helpful getters --- |
| 131 | + |
| 132 | + /** |
| 133 | + * Returns the number of allows used in the current window. |
| 134 | + * |
| 135 | + * @return the number of allows used |
| 136 | + */ |
| 137 | + public int getAllowsUsed() { |
| 138 | + return allowsUsed; |
| 139 | + } |
| 140 | + |
| 141 | + /** |
| 142 | + * Returns the number of allows remaining in the current window. |
| 143 | + * |
| 144 | + * @return the number of allows remaining |
| 145 | + */ |
| 146 | + public int getAllowsRemaining() { |
| 147 | + return Math.max(0, maxAllows - allowsUsed); |
| 148 | + } |
| 149 | + |
| 150 | + /** |
| 151 | + * Returns the window duration in milliseconds. |
| 152 | + * |
| 153 | + * @return the window duration in milliseconds |
| 154 | + */ |
| 155 | + public long getWindowDuration() { |
| 156 | + return windowDurationMs; |
| 157 | + } |
| 158 | + |
| 159 | + /** |
| 160 | + * Returns the maximum number of allows per window. |
| 161 | + * |
| 162 | + * @return the maximum number of allows |
| 163 | + */ |
| 164 | + public int getMaxAllows() { |
| 165 | + return maxAllows; |
| 166 | + } |
| 167 | + |
| 168 | + /** |
| 169 | + * Returns the number of milliseconds until the next window starts. |
| 170 | + * If no window has started yet, returns the full window duration. |
| 171 | + * |
| 172 | + * @return milliseconds until next window |
| 173 | + */ |
| 174 | + public long getMillisUntilNextWindow() { |
| 175 | + if (windowStartMs == 0) return windowDurationMs; |
| 176 | + long nextWindowStart = windowStartMs + windowDurationMs; |
| 177 | + long now = currentTimeMillis(); |
| 178 | + return Math.max(0, nextWindowStart - now); |
| 179 | + } |
| 180 | +} |
0 commit comments