memcache的一致性hash算法
<?php /** * 一致性哈希memcache分布式,采用的是虚拟节点的方式解决分布均匀性问题,查找节点采用二分法快速查找 * the last known user to change this file in the repository <$LastChangedBy: nash.xiong $> * @author nash.xiong <nash.xiong@gmail.com> * @copyright Copyright © 2003-2012 phpd.cn * @license */ class memcacheHashMap { private $_node = array(); private $_nodeData = array(); private $_keyNode = 0; private $_memcache = null; //每个物理服务器生成虚拟节点个数 [注:节点数越多,cache分布的均匀性越好,同时set get操作时,也更耗资源,10台物理服务器,采用200较为合理] private $_virtualNodeNum = 200; private function __construct() { /* 放入配置文件 */ $config = array( '127.0.0.1:11211', '127.0.0.1:11212', '127.0.0.1:11213', '127.0.0.1:11214', '127.0.0.1:11215', ); if(!$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 . '_' . $i; } } ksort($this->_node); } private function __clone() {} /** * 单例,保证只有一个实例 */ static public function getInstance() { static $memcacheObj = null; if(!is_object($memcacheObj)) { $memcacheObj = new self(); } return $memcacheObj; } /** * 根据key做一致性hash后连接到一台物理memcache服务器 * @param string $key */ private function _connectMemcache($key) { $this->_nodeData = array_keys($this->_node); $this->_keyNode = sprintf("%u",crc32($key)); $nodeKey = $this->_findServerNode(); //如果超出环,从头再用二分法查找一个最近的,然后环的头尾做判断,取最接近的节点 if($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; } /** * 采用二分法从虚拟memcache节点中查找最近的节点 * @param unknown_type $m * @param unknown_type $b */ private function _findServerNode($m = 0,$b = 0) { $totle = count($this->_nodeData); if($totle != 0 && $b == 0) $b = $totle - 1; if($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($key); } }
public function add($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); } }