1 | <?php |
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2 | /** |
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3 | * Copyright 2011 Bas de Nooijer. All rights reserved. |
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4 | * |
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5 | * Redistribution and use in source and binary forms, with or without |
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6 | * modification, are permitted provided that the following conditions are met: |
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7 | * |
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8 | * 1. Redistributions of source code must retain the above copyright notice, |
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9 | * this list of conditions and the following disclaimer. |
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10 | * |
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11 | * 2. Redistributions in binary form must reproduce the above copyright notice, |
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12 | * this listof conditions and the following disclaimer in the documentation |
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13 | * and/or other materials provided with the distribution. |
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14 | * |
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15 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER AND CONTRIBUTORS "AS IS" |
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16 | * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
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17 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
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18 | * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE |
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19 | * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
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20 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
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21 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
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22 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
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23 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
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24 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
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25 | * POSSIBILITY OF SUCH DAMAGE. |
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26 | * |
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27 | * The views and conclusions contained in the software and documentation are |
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28 | * those of the authors and should not be interpreted as representing official |
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29 | * policies, either expressed or implied, of the copyright holder. |
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30 | * |
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31 | * @copyright Copyright 2011 Bas de Nooijer <solarium@raspberry.nl> |
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32 | * @license http://github.com/basdenooijer/solarium/raw/master/COPYING |
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33 | * @link http://www.solarium-project.org/ |
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34 | * |
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35 | * @package Solarium |
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36 | */ |
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37 | |
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38 | /** |
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39 | * Weighted random choice class |
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40 | * |
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41 | * For use in the loadbalancer plugin |
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42 | * |
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43 | * @package Solarium |
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44 | * @subpackage Plugin |
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45 | */ |
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46 | class Solarium_Plugin_Loadbalancer_WeightedRandomChoice |
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47 | { |
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48 | |
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49 | /** |
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50 | * Total weight of all choices |
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51 | * |
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52 | * @var int |
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53 | */ |
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54 | protected $_totalWeight = 0; |
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55 | |
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56 | /** |
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57 | * Choices total lookup array |
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58 | * |
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59 | * @var array |
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60 | */ |
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61 | protected $_lookup = array(); |
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62 | |
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63 | /** |
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64 | * Values lookup array |
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65 | * |
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66 | * @var array |
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67 | */ |
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68 | protected $_values = array(); |
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69 | |
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70 | /** |
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71 | * Constructor |
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72 | * |
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73 | * @param array $choices |
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74 | */ |
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75 | public function __construct($choices) |
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76 | { |
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77 | $i = 0; |
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78 | foreach ($choices AS $key => $weight) { |
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79 | if ($weight <=0) throw new Solarium_Exception('Weight must be greater than zero'); |
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80 | |
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81 | $this->_totalWeight += $weight; |
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82 | $this->_lookup[$i] = $this->_totalWeight; |
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83 | $this->_values[$i] = $key; |
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84 | |
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85 | $i++; |
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86 | } |
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87 | } |
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88 | |
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89 | /** |
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90 | * Get a (weighted) random entry |
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91 | * |
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92 | * @param array $excludes Keys to exclude |
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93 | * @return string |
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94 | */ |
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95 | public function getRandom($excludes = array()) |
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96 | { |
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97 | if (count($excludes) == count($this->_values)) { |
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98 | throw new Solarium_Exception('No more server entries available'); |
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99 | } |
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100 | |
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101 | // continue until a non-excluded value is found |
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102 | // @todo optimize? |
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103 | $result = null; |
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104 | while (1) { |
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105 | $result = $this->_values[$this->_getKey()]; |
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106 | if(!in_array($result, $excludes)) break; |
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107 | } |
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108 | |
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109 | return $result; |
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110 | } |
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111 | |
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112 | /** |
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113 | * Get a (weighted) random entry key |
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114 | * |
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115 | * @return int |
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116 | */ |
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117 | protected function _getKey() |
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118 | { |
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119 | $random = mt_rand(1, $this->_totalWeight); |
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120 | $high = count($this->_lookup)-1; |
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121 | $low = 0; |
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122 | |
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123 | while ( $low < $high ) { |
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124 | $probe = (int)(($high + $low) / 2); |
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125 | if ($this->_lookup[$probe] < $random) { |
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126 | $low = $probe + 1; |
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127 | } else if ($this->_lookup[$probe] > $random) { |
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128 | $high = $probe - 1; |
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129 | } else { |
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130 | return $probe; |
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131 | } |
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132 | } |
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133 | |
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134 | if ($this->_lookup[$low] >= $random) { |
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135 | return $low; |
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136 | } else { |
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137 | return $low+1; |
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138 | } |
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139 | |
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140 | } |
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141 | |
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142 | } |
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