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: 630591 $ 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 if (getMaximumRedeliveries() < 0) { 064 return true; 065 } 066 return redeliveryCounter < getMaximumRedeliveries(); 067 } 068 069 // Builder methods 070 // ------------------------------------------------------------------------- 071 072 /** 073 * Sets the maximum number of times a message exchange will be redelivered 074 */ 075 public RedeliveryPolicy maximumRedeliveries(int maximumRedeliveries) { 076 setMaximumRedeliveries(maximumRedeliveries); 077 return this; 078 } 079 080 /** 081 * Sets the initial redelivery delay in milliseconds on the first redelivery 082 */ 083 public RedeliveryPolicy initialRedeliveryDelay(long initialRedeliveryDelay) { 084 setInitialRedeliveryDelay(initialRedeliveryDelay); 085 return this; 086 } 087 088 /** 089 * Enables collision avoidence which adds some randomization to the backoff 090 * timings to reduce contention probability 091 */ 092 public RedeliveryPolicy useCollisionAvoidance() { 093 setUseCollisionAvoidance(true); 094 return this; 095 } 096 097 /** 098 * Enables exponential backof using the {@link #getBackOffMultiplier()} to 099 * increase the time between retries 100 */ 101 public RedeliveryPolicy useExponentialBackOff() { 102 setUseExponentialBackOff(true); 103 return this; 104 } 105 106 /** 107 * Enables exponential backoff and sets the multiplier used to increase the 108 * delay between redeliveries 109 */ 110 public RedeliveryPolicy backOffMultiplier(double multiplier) { 111 useExponentialBackOff(); 112 setBackOffMultiplier(multiplier); 113 return this; 114 } 115 116 /** 117 * Enables collision avoidence and sets the percentage used 118 */ 119 public RedeliveryPolicy collisionAvoidancePercent(double collisionAvoidancePercent) { 120 useCollisionAvoidance(); 121 setCollisionAvoidancePercent(collisionAvoidancePercent); 122 return this; 123 } 124 125 // Properties 126 // ------------------------------------------------------------------------- 127 public double getBackOffMultiplier() { 128 return backOffMultiplier; 129 } 130 131 /** 132 * Sets the multiplier used to increase the delay between redeliveries if 133 * {@link #setUseExponentialBackOff(boolean)} is enabled 134 */ 135 public void setBackOffMultiplier(double backOffMultiplier) { 136 this.backOffMultiplier = backOffMultiplier; 137 } 138 139 public short getCollisionAvoidancePercent() { 140 return (short)Math.round(collisionAvoidanceFactor * 100); 141 } 142 143 /** 144 * Sets the percentage used for collision avoidence if enabled via 145 * {@link #setUseCollisionAvoidance(boolean)} 146 */ 147 public void setCollisionAvoidancePercent(double collisionAvoidancePercent) { 148 this.collisionAvoidanceFactor = collisionAvoidancePercent * 0.01d; 149 } 150 151 public double getCollisionAvoidanceFactor() { 152 return collisionAvoidanceFactor; 153 } 154 155 /** 156 * Sets the factor used for collision avoidence if enabled via 157 * {@link #setUseCollisionAvoidance(boolean)} 158 */ 159 public void setCollisionAvoidanceFactor(double collisionAvoidanceFactor) { 160 this.collisionAvoidanceFactor = collisionAvoidanceFactor; 161 } 162 163 public long getInitialRedeliveryDelay() { 164 return initialRedeliveryDelay; 165 } 166 167 /** 168 * Sets the initial redelivery delay in milliseconds on the first redelivery 169 */ 170 public void setInitialRedeliveryDelay(long initialRedeliveryDelay) { 171 this.initialRedeliveryDelay = initialRedeliveryDelay; 172 } 173 174 public int getMaximumRedeliveries() { 175 return maximumRedeliveries; 176 } 177 178 /** 179 * Sets the maximum number of times a message exchange will be redelivered. 180 * Setting a negative value will retry forever. 181 */ 182 public void setMaximumRedeliveries(int maximumRedeliveries) { 183 this.maximumRedeliveries = maximumRedeliveries; 184 } 185 186 public long getRedeliveryDelay(long previousDelay) { 187 long redeliveryDelay; 188 189 if (previousDelay == 0) { 190 redeliveryDelay = initialRedeliveryDelay; 191 } else if (useExponentialBackOff && backOffMultiplier > 1) { 192 redeliveryDelay = Math.round(backOffMultiplier * previousDelay); 193 } else { 194 redeliveryDelay = previousDelay; 195 } 196 197 if (useCollisionAvoidance) { 198 199 /* 200 * First random determines +/-, second random determines how far to 201 * go in that direction. -cgs 202 */ 203 Random random = getRandomNumberGenerator(); 204 double variance = (random.nextBoolean() ? collisionAvoidanceFactor : -collisionAvoidanceFactor) 205 * random.nextDouble(); 206 redeliveryDelay += redeliveryDelay * variance; 207 } 208 209 return redeliveryDelay; 210 } 211 212 public boolean isUseCollisionAvoidance() { 213 return useCollisionAvoidance; 214 } 215 216 /** 217 * Enables/disables collision avoidence which adds some randomization to the 218 * backoff timings to reduce contention probability 219 */ 220 public void setUseCollisionAvoidance(boolean useCollisionAvoidance) { 221 this.useCollisionAvoidance = useCollisionAvoidance; 222 } 223 224 public boolean isUseExponentialBackOff() { 225 return useExponentialBackOff; 226 } 227 228 /** 229 * Enables/disables exponential backof using the 230 * {@link #getBackOffMultiplier()} to increase the time between retries 231 */ 232 public void setUseExponentialBackOff(boolean useExponentialBackOff) { 233 this.useExponentialBackOff = useExponentialBackOff; 234 } 235 236 protected static synchronized Random getRandomNumberGenerator() { 237 if (randomNumberGenerator == null) { 238 randomNumberGenerator = new Random(); 239 } 240 return randomNumberGenerator; 241 } 242 }