Memcache 分布式存储 【一致性Hash】crc32

class memcacheHash {

    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;

        }

        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];

    }

    /**

     * 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) {

        $total = count($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);

    }

    // 去重添加

    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);

//测试一万次set加get

for($i=0;$i<10000;$i++) {

    $key = md5(mt_rand());

    $b = memcacheHash::getInstance()->set($key, time(), 10);

}

var_dump(number_format(microtime(true) - $runData['BEGIN_TIME'],6));

// 测试直接单台

$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));