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.