利用php怎么實現memcache一致性hash

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實現過程：

memcache的配置 ip+端口+虛擬節點序列號 做hash,使用的是crc32,形成一個閉環。
對要操作的key進行crc32
二分法在虛擬節點環中查找最近的一個虛擬節點
從虛擬節點中提取真實的memcache ip和端口，做單例連接

復制代碼 代碼如下:

<?php
class memcacheHashMap {
        private $_node = array();
        private $_nodeData = array();
        private $_keyNode = 0;
        private $_memcache = null;
        //每個物理服務器生成虛擬節點個數 [注：節點數越多，cache分布的均勻性越好，同時set get操作時，也更耗資源，10臺物理服務器，采用200較為合理]
        private $_virtualNodeNum = 200;
        private function __construct() {
                $config = array(//五個memcache服務器
                                                '127.0.0.1:11211',
                                                '127.0.0.1:11212',
                                                '127.0.0.1:11213',
                                                '127.0.0.1:11214',
                                                '127.0.0.1:11215'
                                        );
                if (!$config) throw new Exception('Cache config NULL');
                foreach ($config as $key => $value) {
                        for ($i = 0; $i < $this->_virtualNodeNum; $i++) {
                                $this->_node[sprintf("%u", crc32($value . '_' . $i))] = $value . '_' . $i;//循環為每個memcache服務器創建200個虛擬節點
                        }
                }
                ksort($this->_node);//創建出來的1000個虛擬節點按照鍵名從小到大排序
        }
        //實例化該類
        static public function getInstance() {
                static $memcacheObj = null;
                if (!is_object($memcacheObj)) {
                        $memcacheObj = new self();
                }
                return $memcacheObj;
        }
        //根據傳來的鍵查找到對應虛擬節點的位置
        private function _connectMemcache($key) {
                $this->_nodeData = array_keys($this->_node);//所有的虛擬節點的鍵的數組
                $this->_keyNode = sprintf("%u", crc32($key));//算出鍵的hash值
                $nodeKey = $this->_findServerNode();//找出對應的虛擬節點
                //如果超出環，從頭再用二分法查找一個最近的，然后環的頭尾做判斷，取最接近的節點
                if ($this->_keyNode > end($this->_nodeData)) {
                        $this->_keyNode -= end($this->_nodeData);
                        $nodeKey2 = $this->_findServerNode();
                        if (abs($nodeKey2 - $this->_keyNode) < abs($nodeKey - $this->_keyNode))  $nodeKey = $nodeKey2;
                }
                var_dump($this->_node[$nodeKey]);
                list($config, $num) = explode('_', $this->_node[$nodeKey]);
                if (!$config) throw new Exception('Cache config Error');
                if (!isset($this->_memcache[$config])) {
                        $this->_memcache[$config] = new Memcache;
                        list($host, $port) = explode(':', $config);
                        $this->_memcache[$config]->connect($host, $port);
                }
                return $this->_memcache[$config];
        }
        //二分法根據給出的值找出最近的虛擬節點位置
        private function _findServerNode($m = 0, $b = 0) {
            $total = count($this->_nodeData);
            if ($total != 0 && $b == 0) $b = $total - 1;
            if ($m < $b){
                $avg = intval(($m+$b) / 2);
                if ($this->_nodeData[$avg] == $this->_keyNode) return $this->_nodeData[$avg];
                elseif ($this->_keyNode < $this->_nodeData[$avg] && ($avg-1 >= 0)) return $this->_findServerNode($m, $avg-1);
                else return $this->_findServerNode($avg+1, $b);
            }
                if (abs($this->_nodeData[$b] - $this->_keyNode) < abs($this->_nodeData[$m] - $this->_keyNode))  return $this->_nodeData[$b];
                else return $this->_nodeData[$m];
        }
        public function set($key, $value, $expire = 0) {
                return $this->_connectMemcache($key)->set($key, json_encode($value), 0, $expire);
        }
        public function add($key, $value, $expire = 0) {
                return $this->_connectMemcache($key)->add($key, json_encode($value), 0, $expire);
        }
        public function get($key) {
                return json_decode($this->_connectMemcache($key)->get($key), true);
        }
        public function delete($key) {
                return $this->_connectMemcache($key)->delete($key);
        }
}
$runData['BEGIN_TIME'] = microtime(true);
//測試一萬次set加get
for($i=0;$i<10000;$i++) {
        $key = md5(mt_rand());
        $b = memcacheHashMap::getInstance()->set($key, time(), 10);
}
var_dump(number_format(microtime(true) - $runData['BEGIN_TIME'],6));
$runData['BEGIN_TIME'] = microtime(true); $m= new Memcache;
$m->connect('127.0.0.1', 11211);
for($i=0;$i<10000;$i++) {
        $key = md5(mt_rand());
        $b = $m->set($key, time(), 0, 10);
}
var_dump(number_format(microtime(true) - $runData['BEGIN_TIME'],6));
?>

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