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));

总结：多台存储会慢一些。具体时间，请自行运行。