一致性哈希memcache php实现

/**
 * 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
 * @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[ $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 );
    }

    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 = 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));
//测试结果，采用一致性哈希分布效率比原生单台速度相差5倍