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| 1 | +/* |
| 2 | + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER. |
| 3 | + * |
| 4 | + * Copyright (c) 2015 Oracle and/or its affiliates. All rights reserved. |
| 5 | + * |
| 6 | + * The contents of this file are subject to the terms of either the GNU |
| 7 | + * General Public License Version 2 only ("GPL") or the Common Development |
| 8 | + * and Distribution License("CDDL") (collectively, the "License"). You |
| 9 | + * may not use this file except in compliance with the License. You can |
| 10 | + * obtain a copy of the License at |
| 11 | + * http://glassfish.java.net/public/CDDL+GPL_1_1.html |
| 12 | + * or packager/legal/LICENSE.txt. See the License for the specific |
| 13 | + * language governing permissions and limitations under the License. |
| 14 | + * |
| 15 | + * When distributing the software, include this License Header Notice in each |
| 16 | + * file and include the License file at packager/legal/LICENSE.txt. |
| 17 | + * |
| 18 | + * GPL Classpath Exception: |
| 19 | + * Oracle designates this particular file as subject to the "Classpath" |
| 20 | + * exception as provided by Oracle in the GPL Version 2 section of the License |
| 21 | + * file that accompanied this code. |
| 22 | + * |
| 23 | + * Modifications: |
| 24 | + * If applicable, add the following below the License Header, with the fields |
| 25 | + * enclosed by brackets [] replaced by your own identifying information: |
| 26 | + * "Portions Copyright [year] [name of copyright owner]" |
| 27 | + * |
| 28 | + * Contributor(s): |
| 29 | + * If you wish your version of this file to be governed by only the CDDL or |
| 30 | + * only the GPL Version 2, indicate your decision by adding "[Contributor] |
| 31 | + * elects to include this software in this distribution under the [CDDL or GPL |
| 32 | + * Version 2] license." If you don't indicate a single choice of license, a |
| 33 | + * recipient has the option to distribute your version of this file under |
| 34 | + * either the CDDL, the GPL Version 2 or to extend the choice of license to |
| 35 | + * its licensees as provided above. However, if you add GPL Version 2 code |
| 36 | + * and therefore, elected the GPL Version 2 license, then the option applies |
| 37 | + * only if the new code is made subject to such option by the copyright |
| 38 | + * holder. |
| 39 | + * |
| 40 | + * This file incorporates work covered by the following copyright and |
| 41 | + * permission notice: |
| 42 | + * |
| 43 | + * Copyright 2010-2013 Coda Hale and Yammer, Inc., 2014-2015 Dropwizard Team |
| 44 | + * |
| 45 | + * Licensed under the Apache License, Version 2.0 (the "License"); |
| 46 | + * you may not use this file except in compliance with the License. |
| 47 | + * You may obtain a copy of the License at |
| 48 | + * |
| 49 | + * http://www.apache.org/licenses/LICENSE-2.0 |
| 50 | + * |
| 51 | + * Unless required by applicable law or agreed to in writing, software |
| 52 | + * distributed under the License is distributed on an "AS IS" BASIS, |
| 53 | + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 54 | + * See the License for the specific language governing permissions and |
| 55 | + * limitations under the License. |
| 56 | + */ |
| 57 | + |
| 58 | +package org.glassfish.jersey.server.internal.monitoring; |
| 59 | + |
| 60 | +import java.util.Collection; |
| 61 | +import java.util.concurrent.ConcurrentNavigableMap; |
| 62 | +import java.util.concurrent.ConcurrentSkipListMap; |
| 63 | +import java.util.concurrent.TimeUnit; |
| 64 | +import java.util.concurrent.atomic.AtomicInteger; |
| 65 | +import java.util.concurrent.atomic.AtomicLong; |
| 66 | + |
| 67 | +/** |
| 68 | + * A {@link TimeReservoir} implementation backed by a sliding window that stores only the measurements made in the last {@code N} |
| 69 | + * seconds (or other startTime unit) and allows an update with data that happened in past (which is what makes it different from |
| 70 | + * Dropwizard's Metrics SlidingTimeWindowReservoir. |
| 71 | + * <p/> |
| 72 | + * The snapshot this reservoir returns has limitations as mentioned in {@link TimeReservoir}. |
| 73 | + * <p/> |
| 74 | + * This reservoir is capable to store up to 2^{@link #COLLISION_BUFFER_POWER}, that is 256, in a granularity of nanoseconds. In |
| 75 | + * other words, up to 256 values that occurred at the same nanosecond can be stored in this reservoir. For particular nanosecond, |
| 76 | + * if the collision buffer exceeds, newly added values are thrown away. |
| 77 | + * |
| 78 | + * @author Stepan Vavra (stepan.vavra at oracle.com) |
| 79 | + * @see <pre><a href="https://github.com/dropwizard/metrics/blob/master/metrics-core/src/main/java/io/dropwizard/metrics/SlidingTimeWindowReservoir.java">Dropwizrd's Metrics SlidingTimeWindowReservoir</a></pre> |
| 80 | + */ |
| 81 | +public class SlidingWindowTimeReservoir implements TimeReservoir { |
| 82 | + |
| 83 | + // allow for 2^that many duplicate ticks before throwing away measurements |
| 84 | + private static final int COLLISION_BUFFER_POWER = 8; |
| 85 | + private static final int COLLISION_BUFFER = 1 << COLLISION_BUFFER_POWER; // 256 |
| 86 | + // only trim on updating once every N |
| 87 | + private static final int TRIM_THRESHOLD = 256; |
| 88 | + |
| 89 | + private final ConcurrentNavigableMap<Long, Long> measurements; |
| 90 | + private final long window; |
| 91 | + private final AtomicLong greatestTick; |
| 92 | + private final AtomicLong updateCount; |
| 93 | + private final long startTick; |
| 94 | + private final AtomicInteger trimOff; |
| 95 | + |
| 96 | + /** |
| 97 | + * Creates a new {@link SlidingWindowTimeReservoir} with the start time and window of startTime. |
| 98 | + * |
| 99 | + * @param window the window of startTime |
| 100 | + * @param windowUnit the unit of {@code window} |
| 101 | + */ |
| 102 | + public SlidingWindowTimeReservoir(long window, TimeUnit windowUnit, long startTime, TimeUnit startTimeUnit) { |
| 103 | + this.measurements = new ConcurrentSkipListMap<>(); |
| 104 | + this.window = windowUnit.toNanos(window) << COLLISION_BUFFER_POWER; |
| 105 | + this.startTick = tick(startTime, startTimeUnit); |
| 106 | + this.greatestTick = new AtomicLong(startTick); |
| 107 | + this.updateCount = new AtomicLong(0); |
| 108 | + this.trimOff = new AtomicInteger(0); |
| 109 | + } |
| 110 | + |
| 111 | + @Override |
| 112 | + public int size(long time, TimeUnit timeUnit) { |
| 113 | + conditionallyUpdateGreatestTick(tick(time, timeUnit)); |
| 114 | + trim(); |
| 115 | + return measurements.size(); |
| 116 | + } |
| 117 | + |
| 118 | + @Override |
| 119 | + public void update(long value, long time, TimeUnit timeUnit) { |
| 120 | + if (updateCount.incrementAndGet() % TRIM_THRESHOLD == 0) { |
| 121 | + trim(); |
| 122 | + } |
| 123 | + |
| 124 | + long tick = tick(time, timeUnit); |
| 125 | + if (greatestTick.get() - window > tick) { |
| 126 | + // the value is too old that it doesn't even fit into the window |
| 127 | + return; |
| 128 | + } |
| 129 | + for (int i = 0; i < COLLISION_BUFFER; ++i) { |
| 130 | + if (measurements.putIfAbsent(tick, value) == null) { |
| 131 | + conditionallyUpdateGreatestTick(tick); |
| 132 | + break; |
| 133 | + } |
| 134 | + // increase the tick, there should be up to COLLISION_BUFFER empty slots |
| 135 | + // where to put the value for given 'time' |
| 136 | + // if empty slot is not found, throw it away as we're getting inaccurate statistics anyway |
| 137 | + tick++; |
| 138 | + } |
| 139 | + } |
| 140 | + |
| 141 | + private long conditionallyUpdateGreatestTick(final long tick) { |
| 142 | + for (;;) { |
| 143 | + final long currentGreatestTick = greatestTick.get(); |
| 144 | + if (tick <= currentGreatestTick) { |
| 145 | + // the tick is too small, return the greatest one |
| 146 | + return currentGreatestTick; |
| 147 | + } |
| 148 | + if (greatestTick.compareAndSet(currentGreatestTick, tick)) { |
| 149 | + // successfully updated greatestTick with the tick |
| 150 | + return tick; |
| 151 | + } |
| 152 | + } |
| 153 | + } |
| 154 | + |
| 155 | + @Override |
| 156 | + public UniformTimeSnapshot getSnapshot(long time, TimeUnit timeUnit) { |
| 157 | + trimOff.incrementAndGet(); |
| 158 | + final long baselineTick = conditionallyUpdateGreatestTick(tick(time, timeUnit)); |
| 159 | + try { |
| 160 | + // now, with the 'baselineTick' we can be sure that no trim will be performed |
| 161 | + // we just cannot guarantee that 'time' will correspond with the 'baselineTick' which is what the API warns about |
| 162 | + final long measuredTickInterval = Math.min(baselineTick - startTick, window); |
| 163 | + final Collection<Long> values = measurements |
| 164 | + .subMap((roundTick(baselineTick)) - measuredTickInterval, true, baselineTick, true) |
| 165 | + .values(); |
| 166 | + return new UniformTimeSnapshot(values, measuredTickInterval >> COLLISION_BUFFER_POWER, TimeUnit.NANOSECONDS); |
| 167 | + } finally { |
| 168 | + trimOff.decrementAndGet(); |
| 169 | + trim(baselineTick); |
| 170 | + } |
| 171 | + } |
| 172 | + |
| 173 | + private long tick(long time, TimeUnit timeUnit) { |
| 174 | + return timeUnit.toNanos(time) << COLLISION_BUFFER_POWER; |
| 175 | + } |
| 176 | + |
| 177 | + private void trim() { |
| 178 | + trim(greatestTick.get()); |
| 179 | + } |
| 180 | + |
| 181 | + private void trim(final long baselineTick) { |
| 182 | + if (trimEnabled()) { |
| 183 | + measurements.headMap(roundTick(baselineTick) - window).clear(); |
| 184 | + } |
| 185 | + } |
| 186 | + |
| 187 | + private boolean trimEnabled() { |
| 188 | + return trimOff.get() == 0; |
| 189 | + } |
| 190 | + |
| 191 | + /** |
| 192 | + * The purpose of this method is to deal with the fact that data for the same nanosecond can be distributed in an interval |
| 193 | + * [0,256). By rounding the tick, we get the tick to which all the other ticks from the same interval belong. |
| 194 | + * |
| 195 | + * @param tick The tick |
| 196 | + * @return The rounded tick |
| 197 | + */ |
| 198 | + private long roundTick(final long tick) { |
| 199 | + // tick / COLLISION_BUFFER * COLLISION_BUFFER |
| 200 | + return tick >> COLLISION_BUFFER_POWER << COLLISION_BUFFER_POWER; |
| 201 | + } |
| 202 | +} |
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