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['a'] = array('weight' => 5, 'current_weight' => 0, 'count' => 0);
$hosts['b'] = array('weight' => 3, 'current_weight' => 0, 'count' => 0);
$hosts['c'] = array('weight' => 2, 'current_weight' => 0, 'count' => 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['weight']; $current['current_weight'] += $weight; $total += $weight; if ( ($best == null) || ($hosts[$best]['current_weight'] < $current['current_weight']) ) { $best = $key; } } $hosts[$best]['current_weight'] -= $total; $hosts[$best]['count']++; $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.