<?php
// php实现负载均衡的加权轮询（WRR）
class WRR {// 每次取100人const num = 100;// 上次取值时间，秒级时间戳public $last_time;// 权重 machine=>weightpublic $machines = array('a' => 3, // 0.6'b' => 1, // 0.2'c' => 1  // 0.2
    );// 占比public $proportion = array();// 用户队列public static $user_ids = array();public function __construct() {// 各机器的占比$total = 0;foreach ($this->machines as $machine => $weight) {$total += $weight;}$this->proportion['a'] = $this->machines['a'] / $total;$this->proportion['b'] = $this->machines['b'] / $total;$this->proportion['c'] = $this->machines['c'] / $total;}public function getUsers() {// 用户人数$cnt = count(self::$user_ids);$a_num = 0;$b_num = 0;$c_num = 0;if ($cnt >= self::num) { // 队列超过100人$a_num = round(self::num * $this->proportion['a']);$b_num = round(self::num * $this->proportion['b']);$c_num = $cnt - $a_num - $b_num;} else { // 队列不足100人$last_time = $this->last_time; // 上次访问时间while (true) {$current_time = $this->getMillisecond();if (($current_time - $last_time) >= 10) { // 当前时间和上一次取值时间超过10ms$a_num = round($cnt * $this->proportion['a']);$b_num = round($cnt * $this->proportion['b']);$c_num = $cnt - $a_num - $b_num;$this->last_time = self::getMillisecond();   // 更新访问时间break;}}}$a = array_splice(self::$user_ids, 0, $a_num);$b = array_splice(self::$user_ids, 0, $b_num);$c = array_splice(self::$user_ids, 0, $c_num);return array('a' => $a,'b' => $b,'c' => $c);}// 获取毫秒级时间戳public function getMillisecond() {list($t1, $t2) = explode(" ", microtime());return (float)sprintf('%.0f', (floatval($t1) + floatval($t2)) * 1000);}
}// 测试
$wrr = new WRR();
for ($i = 0; $i < 3; $i++) {// 模拟持续不断的用户请求$random = rand(10, 120);$user_ids = range(1, $random);WRR::$user_ids = $user_ids;$users = $wrr->getUsers();print_r($users);
}