001 /** 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 package org.apache.camel.processor; 018 019 import java.io.Serializable; 020 import java.util.Random; 021 022 // Code taken from the ActiveMQ codebase 023 024 /** 025 * The policy used to decide how many times to redeliver and the time between 026 * the redeliveries before being sent to a <a 027 * href="http://activemq.apache.org/camel/dead-letter-channel.html">Dead Letter 028 * Channel</a> 029 * 030 * @version $Revision: 565361 $ 031 */ 032 public class RedeliveryPolicy implements Cloneable, Serializable { 033 protected static transient Random randomNumberGenerator; 034 protected int maximumRedeliveries = 6; 035 protected long initialRedeliveryDelay = 1000L; 036 protected double backOffMultiplier = 2; 037 protected boolean useExponentialBackOff; 038 // +/-15% for a 30% spread -cgs 039 protected double collisionAvoidanceFactor = 0.15d; 040 protected boolean useCollisionAvoidance; 041 042 public RedeliveryPolicy() { 043 } 044 045 @Override 046 public String toString() { 047 return "RedeliveryPolicy[maximumRedeliveries=" + maximumRedeliveries + "]"; 048 } 049 050 public RedeliveryPolicy copy() { 051 try { 052 return (RedeliveryPolicy)clone(); 053 } catch (CloneNotSupportedException e) { 054 throw new RuntimeException("Could not clone: " + e, e); 055 } 056 } 057 058 /** 059 * Returns true if the policy decides that the message exchange should be 060 * redelivered 061 */ 062 public boolean shouldRedeliver(int redeliveryCounter) { 063 return redeliveryCounter < getMaximumRedeliveries(); 064 } 065 066 // Builder methods 067 // ------------------------------------------------------------------------- 068 069 /** 070 * Sets the maximum number of times a message exchange will be redelivered 071 */ 072 public RedeliveryPolicy maximumRedeliveries(int maximumRedeliveries) { 073 setMaximumRedeliveries(maximumRedeliveries); 074 return this; 075 } 076 077 /** 078 * Sets the initial redelivery delay in milliseconds on the first redelivery 079 */ 080 public RedeliveryPolicy initialRedeliveryDelay(long initialRedeliveryDelay) { 081 setInitialRedeliveryDelay(initialRedeliveryDelay); 082 return this; 083 } 084 085 /** 086 * Enables collision avoidence which adds some randomization to the backoff 087 * timings to reduce contention probability 088 */ 089 public RedeliveryPolicy useCollisionAvoidance() { 090 setUseCollisionAvoidance(true); 091 return this; 092 } 093 094 /** 095 * Enables exponential backof using the {@link #getBackOffMultiplier()} to 096 * increase the time between retries 097 */ 098 public RedeliveryPolicy useExponentialBackOff() { 099 setUseExponentialBackOff(true); 100 return this; 101 } 102 103 /** 104 * Enables exponential backoff and sets the multiplier used to increase the 105 * delay between redeliveries 106 */ 107 public RedeliveryPolicy backOffMultiplier(double multiplier) { 108 useExponentialBackOff(); 109 setBackOffMultiplier(multiplier); 110 return this; 111 } 112 113 /** 114 * Enables collision avoidence and sets the percentage used 115 */ 116 public RedeliveryPolicy collisionAvoidancePercent(double collisionAvoidancePercent) { 117 useCollisionAvoidance(); 118 setCollisionAvoidancePercent(collisionAvoidancePercent); 119 return this; 120 } 121 122 // Properties 123 // ------------------------------------------------------------------------- 124 public double getBackOffMultiplier() { 125 return backOffMultiplier; 126 } 127 128 /** 129 * Sets the multiplier used to increase the delay between redeliveries if 130 * {@link #setUseExponentialBackOff(boolean)} is enabled 131 */ 132 public void setBackOffMultiplier(double backOffMultiplier) { 133 this.backOffMultiplier = backOffMultiplier; 134 } 135 136 public short getCollisionAvoidancePercent() { 137 return (short)Math.round(collisionAvoidanceFactor * 100); 138 } 139 140 /** 141 * Sets the percentage used for collision avoidence if enabled via 142 * {@link #setUseCollisionAvoidance(boolean)} 143 */ 144 public void setCollisionAvoidancePercent(double collisionAvoidancePercent) { 145 this.collisionAvoidanceFactor = collisionAvoidancePercent * 0.01d; 146 } 147 148 public double getCollisionAvoidanceFactor() { 149 return collisionAvoidanceFactor; 150 } 151 152 /** 153 * Sets the factor used for collision avoidence if enabled via 154 * {@link #setUseCollisionAvoidance(boolean)} 155 */ 156 public void setCollisionAvoidanceFactor(double collisionAvoidanceFactor) { 157 this.collisionAvoidanceFactor = collisionAvoidanceFactor; 158 } 159 160 public long getInitialRedeliveryDelay() { 161 return initialRedeliveryDelay; 162 } 163 164 /** 165 * Sets the initial redelivery delay in milliseconds on the first redelivery 166 */ 167 public void setInitialRedeliveryDelay(long initialRedeliveryDelay) { 168 this.initialRedeliveryDelay = initialRedeliveryDelay; 169 } 170 171 public int getMaximumRedeliveries() { 172 return maximumRedeliveries; 173 } 174 175 /** 176 * Sets the maximum number of times a message exchange will be redelivered 177 */ 178 public void setMaximumRedeliveries(int maximumRedeliveries) { 179 this.maximumRedeliveries = maximumRedeliveries; 180 } 181 182 public long getRedeliveryDelay(long previousDelay) { 183 long redeliveryDelay; 184 185 if (previousDelay == 0) { 186 redeliveryDelay = initialRedeliveryDelay; 187 } else if (useExponentialBackOff && backOffMultiplier > 1) { 188 redeliveryDelay = Math.round(backOffMultiplier * previousDelay); 189 } else { 190 redeliveryDelay = previousDelay; 191 } 192 193 if (useCollisionAvoidance) { 194 195 /* 196 * First random determines +/-, second random determines how far to 197 * go in that direction. -cgs 198 */ 199 Random random = getRandomNumberGenerator(); 200 double variance = (random.nextBoolean() ? collisionAvoidanceFactor : -collisionAvoidanceFactor) 201 * random.nextDouble(); 202 redeliveryDelay += redeliveryDelay * variance; 203 } 204 205 return redeliveryDelay; 206 } 207 208 public boolean isUseCollisionAvoidance() { 209 return useCollisionAvoidance; 210 } 211 212 /** 213 * Enables/disables collision avoidence which adds some randomization to the 214 * backoff timings to reduce contention probability 215 */ 216 public void setUseCollisionAvoidance(boolean useCollisionAvoidance) { 217 this.useCollisionAvoidance = useCollisionAvoidance; 218 } 219 220 public boolean isUseExponentialBackOff() { 221 return useExponentialBackOff; 222 } 223 224 /** 225 * Enables/disables exponential backof using the 226 * {@link #getBackOffMultiplier()} to increase the time between retries 227 */ 228 public void setUseExponentialBackOff(boolean useExponentialBackOff) { 229 this.useExponentialBackOff = useExponentialBackOff; 230 } 231 232 protected static synchronized Random getRandomNumberGenerator() { 233 if (randomNumberGenerator == null) { 234 randomNumberGenerator = new Random(); 235 } 236 return randomNumberGenerator; 237 } 238 }