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 * @version $Revision: 1.11 $ 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 initialRedeliveryDelay = 1000L; 038 private boolean useCollisionAvoidance; 039 private boolean useExponentialBackOff; 040 private double backOffMultiplier = 5.0; 041 042 public RedeliveryPolicy() { 043 } 044 045 public RedeliveryPolicy copy() { 046 try { 047 return (RedeliveryPolicy)clone(); 048 } catch (CloneNotSupportedException e) { 049 throw new RuntimeException("Could not clone: " + e, e); 050 } 051 } 052 053 public double getBackOffMultiplier() { 054 return backOffMultiplier; 055 } 056 057 public void setBackOffMultiplier(double backOffMultiplier) { 058 this.backOffMultiplier = backOffMultiplier; 059 } 060 061 public short getCollisionAvoidancePercent() { 062 return (short)Math.round(collisionAvoidanceFactor * 100); 063 } 064 065 public void setCollisionAvoidancePercent(short collisionAvoidancePercent) { 066 this.collisionAvoidanceFactor = collisionAvoidancePercent * 0.01d; 067 } 068 069 public long getInitialRedeliveryDelay() { 070 return initialRedeliveryDelay; 071 } 072 073 public void setInitialRedeliveryDelay(long initialRedeliveryDelay) { 074 this.initialRedeliveryDelay = initialRedeliveryDelay; 075 } 076 077 public int getMaximumRedeliveries() { 078 return maximumRedeliveries; 079 } 080 081 public void setMaximumRedeliveries(int maximumRedeliveries) { 082 this.maximumRedeliveries = maximumRedeliveries; 083 } 084 085 public long getRedeliveryDelay(long previousDelay) { 086 long redeliveryDelay; 087 088 if (previousDelay == 0) { 089 redeliveryDelay = initialRedeliveryDelay; 090 } else if (useExponentialBackOff && backOffMultiplier > 1) { 091 redeliveryDelay = (long) (previousDelay * backOffMultiplier); 092 } else { 093 redeliveryDelay = previousDelay; 094 } 095 096 if (useCollisionAvoidance) { 097 /* 098 * First random determines +/-, second random determines how far to 099 * go in that direction. -cgs 100 */ 101 Random random = getRandomNumberGenerator(); 102 double variance = (random.nextBoolean() ? collisionAvoidanceFactor : -collisionAvoidanceFactor) * random.nextDouble(); 103 redeliveryDelay += redeliveryDelay * variance; 104 } 105 106 return redeliveryDelay; 107 } 108 109 public boolean isUseCollisionAvoidance() { 110 return useCollisionAvoidance; 111 } 112 113 public void setUseCollisionAvoidance(boolean useCollisionAvoidance) { 114 this.useCollisionAvoidance = useCollisionAvoidance; 115 } 116 117 public boolean isUseExponentialBackOff() { 118 return useExponentialBackOff; 119 } 120 121 public void setUseExponentialBackOff(boolean useExponentialBackOff) { 122 this.useExponentialBackOff = useExponentialBackOff; 123 } 124 125 protected static synchronized Random getRandomNumberGenerator() { 126 if (randomNumberGenerator == null) { 127 randomNumberGenerator = new Random(); 128 } 129 return randomNumberGenerator; 130 } 131 132 }