round robin权重轮循算法php实现代码

先上代码，采用php脚本语言

<?php
 
/* 
 * Copyright (C) FatHong
 */
 
/* 数据初始化，weight: 权重 */
$hosts[&#39;a&#39;] = array(&#39;weight&#39; => 5, &#39;current_weight&#39; => 0, &#39;count&#39; => 0);
$hosts[&#39;b&#39;] = array(&#39;weight&#39; => 3, &#39;current_weight&#39; => 0, &#39;count&#39; => 0);
$hosts[&#39;c&#39;] = array(&#39;weight&#39; => 2, &#39;current_weight&#39; => 0, &#39;count&#39; => 0);
 
$result = array();
 
/* 模拟10次 */
for ($i = 0; $i < 10; $i++) {
  round_robin($hosts, $result);
}
 
/* 输出结果 */
print_r($result);
 
/* round robin 轮循 */
function round_robin(&$hosts, &$result)
{
  $total = 0;
  $best = null;
 
  foreach ($hosts as $key => $item) {
    $current = &$hosts[$key];
    $weight = $current[&#39;weight&#39;];
 
    $current[&#39;current_weight&#39;] += $weight;
    $total += $weight;
 
    if ( ($best == null) || ($hosts[$best][&#39;current_weight&#39;] < 
                $current[&#39;current_weight&#39;]) ) 
    {
      $best = $key;
    }
  }
 
  $hosts[$best][&#39;current_weight&#39;] -= $total;
  $hosts[$best][&#39;count&#39;]++;
 
  $result[] = $best;
}

输出结果：

Array
(
[0] => a
[1] => b
[2] => c
[3] => a
[4] => a
[5] => b
[6] => a
[7] => c
[8] => b
[9] => a
)

负载均衡的服务器中，其实现算法有种是round-robin权重轮循，就是后端的服务器列表中，给每个服务器标上权重，代表它被采用的机率。

这段代码把最简洁的流程剥离出来，没考虑后端挂起等情况，可以知道它是怎么实现的，仅供参考.

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