Classes in this File | Line Coverage | Branch Coverage | Complexity | ||||||||
StickyLoadBalancer |
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| 0.0;0 |
1 | /** |
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2 | * Licensed to the Apache Software Foundation (ASF) under one or more |
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3 | * contributor license agreements. See the NOTICE file distributed with |
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4 | * this work for additional information regarding copyright ownership. |
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5 | * The ASF licenses this file to You under the Apache License, Version 2.0 |
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6 | * (the "License"); you may not use this file except in compliance with |
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7 | * the License. You may obtain a copy of the License at |
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8 | * |
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9 | * http://www.apache.org/licenses/LICENSE-2.0 |
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10 | * |
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11 | * Unless required by applicable law or agreed to in writing, software |
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12 | * distributed under the License is distributed on an "AS IS" BASIS, |
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13 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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14 | * See the License for the specific language governing permissions and |
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15 | * limitations under the License. |
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16 | */ |
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17 | package org.apache.camel.processor.loadbalancer; |
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18 | ||
19 | import java.util.HashMap; |
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20 | import java.util.Iterator; |
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21 | import java.util.List; |
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22 | import java.util.Map; |
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23 | ||
24 | import org.apache.camel.Exchange; |
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25 | import org.apache.camel.Expression; |
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26 | import org.apache.camel.Processor; |
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27 | ||
28 | /** |
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29 | * Implements a sticky load balancer using an {@link Expression} to calculate |
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30 | * a correlation key to perform the sticky load balancing; rather like jsessionid in the web |
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31 | * or JMSXGroupID in JMS. |
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32 | * |
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33 | * @version $Revision: 1.1 $ |
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34 | */ |
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35 | public class StickyLoadBalancer extends QueueLoadBalancer { |
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36 | private Expression<Exchange> correlationExpression; |
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37 | private QueueLoadBalancer loadBalancer; |
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38 | 0 | private int numberOfHashGroups = 64 * 1024; |
39 | 0 | private Map<Object, Processor> stickyMap = new HashMap<Object, Processor>(); |
40 | ||
41 | public StickyLoadBalancer(Expression<Exchange> correlationExpression) { |
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42 | 0 | this(correlationExpression, new RoundRobinLoadBalancer()); |
43 | 0 | } |
44 | ||
45 | 0 | public StickyLoadBalancer(Expression<Exchange> correlationExpression, QueueLoadBalancer loadBalancer) { |
46 | 0 | this.correlationExpression = correlationExpression; |
47 | 0 | this.loadBalancer = loadBalancer; |
48 | 0 | } |
49 | ||
50 | protected synchronized Processor chooseProcessor(List<Processor> processors, Exchange exchange) { |
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51 | 0 | Object value = correlationExpression.evaluate(exchange); |
52 | 0 | Object key = getStickyKey(value); |
53 | ||
54 | Processor processor; |
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55 | 0 | synchronized (stickyMap) { |
56 | 0 | processor = stickyMap.get(key); |
57 | 0 | if (processor == null) { |
58 | 0 | processor = loadBalancer.chooseProcessor(processors, exchange); |
59 | 0 | stickyMap.put(key, processor); |
60 | } |
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61 | 0 | } |
62 | 0 | return processor; |
63 | } |
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64 | ||
65 | @Override |
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66 | public void removeProcessor(Processor processor) { |
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67 | 0 | synchronized (stickyMap) { |
68 | 0 | Iterator<Map.Entry<Object, Processor>> iter = stickyMap.entrySet().iterator(); |
69 | 0 | while (iter.hasNext()) { |
70 | 0 | Map.Entry<Object, Processor> entry = iter.next(); |
71 | 0 | if (processor.equals(entry.getValue())) { |
72 | 0 | iter.remove(); |
73 | } |
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74 | 0 | } |
75 | 0 | } |
76 | 0 | super.removeProcessor(processor); |
77 | 0 | } |
78 | ||
79 | ||
80 | // Properties |
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81 | //------------------------------------------------------------------------- |
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82 | public int getNumberOfHashGroups() { |
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83 | 0 | return numberOfHashGroups; |
84 | } |
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85 | ||
86 | public void setNumberOfHashGroups(int numberOfHashGroups) { |
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87 | 0 | this.numberOfHashGroups = numberOfHashGroups; |
88 | 0 | } |
89 | ||
90 | // Implementation methods |
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91 | //------------------------------------------------------------------------- |
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92 | ||
93 | /** |
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94 | * A strategy to create the key for the sticky load balancing map. |
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95 | * The default implementation uses the hash code of the value |
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96 | * then modulos by the numberOfHashGroups to avoid the sticky map getting too big |
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97 | * |
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98 | * @param value the correlation value |
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99 | * @return the key to be used in the sticky map |
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100 | */ |
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101 | protected Object getStickyKey(Object value) { |
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102 | 0 | int hashCode = 37; |
103 | 0 | if (value != null) { |
104 | 0 | hashCode = value.hashCode(); |
105 | } |
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106 | 0 | if (numberOfHashGroups > 0) { |
107 | 0 | hashCode = hashCode % numberOfHashGroups; |
108 | } |
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109 | 0 | return hashCode; |
110 | } |
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111 | } |