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.activemq; 018 019 import java.io.Serializable; 020 import java.util.Random; 021 022 /** 023 * Configuration options used to control how messages are re-delivered when they 024 * are rolled back. 025 * 026 * @org.apache.xbean.XBean element="redeliveryPolicy" 027 * 028 */ 029 public class RedeliveryPolicy implements Cloneable, Serializable { 030 031 public static final int NO_MAXIMUM_REDELIVERIES = -1; 032 private static Random randomNumberGenerator; 033 034 // +/-15% for a 30% spread -cgs 035 private double collisionAvoidanceFactor = 0.15d; 036 private int maximumRedeliveries = 6; 037 private long maximumRedeliveryDelay = -1; 038 private long initialRedeliveryDelay = 1000L; 039 private boolean useCollisionAvoidance; 040 private boolean useExponentialBackOff; 041 private double backOffMultiplier = 5.0; 042 private long redeliveryDelay = initialRedeliveryDelay; 043 044 public RedeliveryPolicy() { 045 } 046 047 public RedeliveryPolicy copy() { 048 try { 049 return (RedeliveryPolicy)clone(); 050 } catch (CloneNotSupportedException e) { 051 throw new RuntimeException("Could not clone: " + e, e); 052 } 053 } 054 055 public double getBackOffMultiplier() { 056 return backOffMultiplier; 057 } 058 059 public void setBackOffMultiplier(double backOffMultiplier) { 060 this.backOffMultiplier = backOffMultiplier; 061 } 062 063 public short getCollisionAvoidancePercent() { 064 return (short)Math.round(collisionAvoidanceFactor * 100); 065 } 066 067 public void setCollisionAvoidancePercent(short collisionAvoidancePercent) { 068 this.collisionAvoidanceFactor = collisionAvoidancePercent * 0.01d; 069 } 070 071 public long getInitialRedeliveryDelay() { 072 return initialRedeliveryDelay; 073 } 074 075 public void setInitialRedeliveryDelay(long initialRedeliveryDelay) { 076 this.initialRedeliveryDelay = initialRedeliveryDelay; 077 } 078 079 public long getMaximumRedeliveryDelay() { 080 return maximumRedeliveryDelay; 081 } 082 083 public void setMaximumRedeliveryDelay(long maximumRedeliveryDelay) { 084 this.maximumRedeliveryDelay = maximumRedeliveryDelay; 085 } 086 087 public int getMaximumRedeliveries() { 088 return maximumRedeliveries; 089 } 090 091 public void setMaximumRedeliveries(int maximumRedeliveries) { 092 this.maximumRedeliveries = maximumRedeliveries; 093 } 094 095 public long getNextRedeliveryDelay(long previousDelay) { 096 long nextDelay; 097 098 if (previousDelay == 0) { 099 nextDelay = redeliveryDelay; 100 } else if (useExponentialBackOff && backOffMultiplier > 1) { 101 nextDelay = (long) (previousDelay * backOffMultiplier); 102 if(maximumRedeliveryDelay != -1 && nextDelay > maximumRedeliveryDelay) { 103 // in case the user made max redelivery delay less than redelivery delay for some reason. 104 nextDelay = Math.max(maximumRedeliveryDelay, redeliveryDelay); 105 } 106 } else { 107 nextDelay = previousDelay; 108 } 109 110 if (useCollisionAvoidance) { 111 /* 112 * First random determines +/-, second random determines how far to 113 * go in that direction. -cgs 114 */ 115 Random random = getRandomNumberGenerator(); 116 double variance = (random.nextBoolean() ? collisionAvoidanceFactor : -collisionAvoidanceFactor) * random.nextDouble(); 117 nextDelay += nextDelay * variance; 118 } 119 120 return nextDelay; 121 } 122 123 public boolean isUseCollisionAvoidance() { 124 return useCollisionAvoidance; 125 } 126 127 public void setUseCollisionAvoidance(boolean useCollisionAvoidance) { 128 this.useCollisionAvoidance = useCollisionAvoidance; 129 } 130 131 public boolean isUseExponentialBackOff() { 132 return useExponentialBackOff; 133 } 134 135 public void setUseExponentialBackOff(boolean useExponentialBackOff) { 136 this.useExponentialBackOff = useExponentialBackOff; 137 } 138 139 protected static synchronized Random getRandomNumberGenerator() { 140 if (randomNumberGenerator == null) { 141 randomNumberGenerator = new Random(); 142 } 143 return randomNumberGenerator; 144 } 145 146 public void setRedeliveryDelay(long redeliveryDelay) { 147 this.redeliveryDelay = redeliveryDelay; 148 } 149 150 public long getRedeliveryDelay() { 151 return redeliveryDelay; 152 } 153 }