Memcache 分佈式存儲 【一致性Hash】crc32

class memcacheHash {

    private $_node = array();
    private $_nodeData = array();
    private $_keyNode = 0;
    private $_memcache = null;
    
    //每一個物理服務器生成虛擬節點個數 [注：節點數越多，cache分佈的均勻性越好，同時set get操做時，也更耗資源，10臺物理服務器，採用200較爲合理]
    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(){}
    
    /**
     * 單例，保證只有一個實例
     */
    static public function getInstance() {
        static $memcacheObj = null;
        if (!is_object($memcacheObj)) {
                $memcacheObj = new self();
        }
        return $memcacheObj;
    }
    
    /**
     * 根據key作一致性hash後鏈接到一臺物理memcache服務器
     * @param string $key
     */
    private function _connectMemcache($key) {
        $this->_nodeData = array_keys($this->_node);
        $this->_keyNode = sprintf("%u", crc32($key));
        $nodeKey = $this->_findServerNode();
        //若是超出環，從頭再用二分法查找一個最近的，而後環的頭尾作判斷，取最接近的節點
        if ($this->_keyNode > end($this->_nodeData)) {
            $this->_keyNode -= end($this->_nodeData);
            $nodeKey2 = $this->_findServerNode();
            if (abs($nodeKey2 - $this->_keyNode) < abs($nodeKey - $this->_keyNode))  $nodeKey = $nodeKey2;
        }
        list($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];
    }
    
    /**
     * 採用二分法從虛擬memcache節點中查找最近的節點
     * @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);
    }
         
}

$runData['BEGIN_TIME'] = microtime(true);
//測試一萬次set加get
for($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));

// 測試直接單臺
$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));

總結：多臺存儲會慢一些。具體時間，請自行運行。