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1
18 package org.apache.activemq;
19
20 import java.io.Serializable  ;
21 import java.util.Random ;
22
23
31 public class RedeliveryPolicy implements Cloneable , Serializable {
32
33 public static final int NO_MAXIMUM_REDELIVERIES = -1;
34
35 protected double collisionAvoidanceFactor = 0.15d;
37 protected int maximumRedeliveries = 6;
38 protected long initialRedeliveryDelay = 1000L;
39 protected static Random randomNumberGenerator;
40 protected boolean useCollisionAvoidance = false;
41 protected boolean useExponentialBackOff = false;
42 protected short backOffMultiplier = 5;
43
44 public RedeliveryPolicy() {
45 }
46
47 public RedeliveryPolicy copy() {
48 try {
49 return (RedeliveryPolicy) clone();
50 }
51 catch (CloneNotSupportedException e) {
52 throw new RuntimeException ("Could not clone: " + e, e);
53 }
54 }
55
56 public short getBackOffMultiplier() {
57 return backOffMultiplier;
58 }
59
60 public void setBackOffMultiplier(short backOffMultiplier) {
61 this.backOffMultiplier = backOffMultiplier;
62 }
63
64 public short getCollisionAvoidancePercent() {
65 return (short) Math.round(collisionAvoidanceFactor * 100);
66 }
67
68 public void setCollisionAvoidancePercent(short collisionAvoidancePercent) {
69 this.collisionAvoidanceFactor = collisionAvoidancePercent * 0.01d;
70 }
71
72 public long getInitialRedeliveryDelay() {
73 return initialRedeliveryDelay;
74 }
75
76 public void setInitialRedeliveryDelay(long initialRedeliveryDelay) {
77 this.initialRedeliveryDelay = initialRedeliveryDelay;
78 }
79
80 public int getMaximumRedeliveries() {
81 return maximumRedeliveries;
82 }
83
84 public void setMaximumRedeliveries(int maximumRedeliveries) {
85 this.maximumRedeliveries = maximumRedeliveries;
86 }
87
88 public long getRedeliveryDelay(long previousDelay) {
89 long redeliveryDelay;
90
91 if (previousDelay == 0) {
92 redeliveryDelay = initialRedeliveryDelay;
93 } else if (useExponentialBackOff && backOffMultiplier > 1) {
94 redeliveryDelay = previousDelay * backOffMultiplier;
95 } else {
96 redeliveryDelay = previousDelay;
97 }
98
99 if (useCollisionAvoidance) {
100
104 Random random = getRandomNumberGenerator();
105 double variance = (random.nextBoolean() ? collisionAvoidanceFactor : -collisionAvoidanceFactor) * random.nextDouble();
106 redeliveryDelay += redeliveryDelay * variance;
107 }
108
109 return redeliveryDelay;
110 }
111
112 public boolean isUseCollisionAvoidance() {
113 return useCollisionAvoidance;
114 }
115
116 public void setUseCollisionAvoidance(boolean useCollisionAvoidance) {
117 this.useCollisionAvoidance = useCollisionAvoidance;
118 }
119
120 public boolean isUseExponentialBackOff() {
121 return useExponentialBackOff;
122 }
123
124 public void setUseExponentialBackOff(boolean useExponentialBackOff) {
125 this.useExponentialBackOff = useExponentialBackOff;
126 }
127
128 protected static synchronized Random getRandomNumberGenerator() {
129 if (randomNumberGenerator == null) {
130 randomNumberGenerator = new Random ();
131 }
132 return randomNumberGenerator;
133 }
134
135 }
136
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