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 */ 017package org.apache.activemq; 018 019import java.io.Serializable; 020import java.util.Random; 021import org.apache.activemq.filter.DestinationMapEntry; 022import org.apache.activemq.util.IntrospectionSupport; 023 024/** 025 * Configuration options for a messageConsumer used to control how messages are re-delivered when they 026 * are rolled back. 027 * May be used server side on a per destination basis via the Broker RedeliveryPlugin 028 * 029 * @org.apache.xbean.XBean element="redeliveryPolicy" 030 * 031 */ 032public class RedeliveryPolicy extends DestinationMapEntry implements Cloneable, Serializable { 033 034 public static final int NO_MAXIMUM_REDELIVERIES = -1; 035 public static final int DEFAULT_MAXIMUM_REDELIVERIES = 6; 036 037 private static Random randomNumberGenerator; 038 039 // +/-15% for a 30% spread -cgs 040 protected double collisionAvoidanceFactor = 0.15d; 041 protected int maximumRedeliveries = DEFAULT_MAXIMUM_REDELIVERIES; 042 protected long maximumRedeliveryDelay = -1; 043 protected long initialRedeliveryDelay = 1000L; 044 protected boolean useCollisionAvoidance; 045 protected boolean useExponentialBackOff; 046 protected double backOffMultiplier = 5.0; 047 protected long redeliveryDelay = initialRedeliveryDelay; 048 protected boolean preDispatchCheck = true; 049 050 public RedeliveryPolicy() { 051 } 052 053 public RedeliveryPolicy copy() { 054 try { 055 return (RedeliveryPolicy)clone(); 056 } catch (CloneNotSupportedException e) { 057 throw new RuntimeException("Could not clone: " + e, e); 058 } 059 } 060 061 public double getBackOffMultiplier() { 062 return backOffMultiplier; 063 } 064 065 public void setBackOffMultiplier(double backOffMultiplier) { 066 this.backOffMultiplier = backOffMultiplier; 067 } 068 069 public short getCollisionAvoidancePercent() { 070 return (short)Math.round(collisionAvoidanceFactor * 100); 071 } 072 073 public void setCollisionAvoidancePercent(short collisionAvoidancePercent) { 074 this.collisionAvoidanceFactor = collisionAvoidancePercent * 0.01d; 075 } 076 077 public long getInitialRedeliveryDelay() { 078 return initialRedeliveryDelay; 079 } 080 081 public void setInitialRedeliveryDelay(long initialRedeliveryDelay) { 082 this.initialRedeliveryDelay = initialRedeliveryDelay; 083 } 084 085 public long getMaximumRedeliveryDelay() { 086 return maximumRedeliveryDelay; 087 } 088 089 public void setMaximumRedeliveryDelay(long maximumRedeliveryDelay) { 090 this.maximumRedeliveryDelay = maximumRedeliveryDelay; 091 } 092 093 public int getMaximumRedeliveries() { 094 return maximumRedeliveries; 095 } 096 097 public void setMaximumRedeliveries(int maximumRedeliveries) { 098 this.maximumRedeliveries = maximumRedeliveries; 099 } 100 101 public long getNextRedeliveryDelay(long previousDelay) { 102 long nextDelay = redeliveryDelay; 103 104 if (previousDelay > 0 && useExponentialBackOff && backOffMultiplier > 1) { 105 nextDelay = (long) (previousDelay * backOffMultiplier); 106 if(maximumRedeliveryDelay != -1 && nextDelay > maximumRedeliveryDelay) { 107 // in case the user made max redelivery delay less than redelivery delay for some reason. 108 nextDelay = Math.max(maximumRedeliveryDelay, redeliveryDelay); 109 } 110 } 111 112 if (useCollisionAvoidance) { 113 /* 114 * First random determines +/-, second random determines how far to 115 * go in that direction. -cgs 116 */ 117 Random random = getRandomNumberGenerator(); 118 double variance = (random.nextBoolean() ? collisionAvoidanceFactor : -collisionAvoidanceFactor) * random.nextDouble(); 119 nextDelay += nextDelay * variance; 120 } 121 122 return nextDelay; 123 } 124 125 public boolean isUseCollisionAvoidance() { 126 return useCollisionAvoidance; 127 } 128 129 public void setUseCollisionAvoidance(boolean useCollisionAvoidance) { 130 this.useCollisionAvoidance = useCollisionAvoidance; 131 } 132 133 public boolean isUseExponentialBackOff() { 134 return useExponentialBackOff; 135 } 136 137 public void setUseExponentialBackOff(boolean useExponentialBackOff) { 138 this.useExponentialBackOff = useExponentialBackOff; 139 } 140 141 protected static synchronized Random getRandomNumberGenerator() { 142 if (randomNumberGenerator == null) { 143 randomNumberGenerator = new Random(); 144 } 145 return randomNumberGenerator; 146 } 147 148 public void setRedeliveryDelay(long redeliveryDelay) { 149 this.redeliveryDelay = redeliveryDelay; 150 } 151 152 public long getRedeliveryDelay() { 153 return redeliveryDelay; 154 } 155 156 @Override 157 public String toString() { 158 return IntrospectionSupport.toString(this, DestinationMapEntry.class, null); 159 } 160 161 public void setPreDispatchCheck(boolean preDispatchCheck) { 162 this.preDispatchCheck = preDispatchCheck; 163 } 164 165 public boolean isPreDispatchCheck() { 166 return preDispatchCheck; 167 } 168}