為什么80%的碼農都做不了架構師？>>> ??

先上代碼，采用php腳本語言

<?php/* * Copyright (C) FatHong*//* 數據初始化，weight: 權重 */ $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();/* 模擬10次 */ for ($i = 0; $i < 10; $i++) {round_robin($hosts, $result); }/* 輸出結果 */ print_r($result);/* round robin 輪循 */ 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; }

輸出結果：

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

負載均衡的服務器中，其實現算法有種是round-robin權重輪循，就是后端的服務器列表中，給每個服務器標上權重，代表它被采用的機率。

這段代碼把最簡潔的流程剝離出來，沒考慮后端掛起等情況，可以知道它是怎么實現的，僅供參考.

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轉載于:https://my.oschina.net/fqing/blog/79161

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