PHP實現：一致性HASH演算法

<?php// +----------------------------------------------------------------------// | Perfect Is Shit// +----------------------------------------------------------------------// | PHP實現：一致性HASH演算法// +----------------------------------------------------------------------// | Author: alexander <gt199899@gmail.com>// +----------------------------------------------------------------------// | Datetime: 2017-01-11 16:01:36// +----------------------------------------------------------------------// | Copyright: Perfect Is Shit// +----------------------------------------------------------------------class ConsistentHashing{    // 圓環    // hash -> 節點    private $_ring = array();    // 所有節點    // 節點 -> hash    public $nodes = array();    // 每個節點的虛擬節點    public $virtual = 64;    /**     * 構造     * @param array $nodes 初始化的節點列表     */    public function __construct($nodes = array())    {        if (!empty($nodes)) {            foreach ($nodes as $value) {                $this->addNode($value);            }        }    }    /**     * 擷取圓環內容     * @return array $this->_ring     */    public function getRing()    {        return $this->_ring;    }    /**     * time33 函數     * @param  string $str     * @return 32位正整數     * @author 大神們     */    public function time33($str)    {        // hash(i) = hash(i-1) * 33 + str[i]        // $hash = 5381; ## 將hash設定為0，竟然比設定為5381分布效果更好。。。        $hash = 0;        $s    = md5($str); //相比其它版本，進行了md5加密        $seed = 5;        $len  = 32;//加密後長度32        for ($i = 0; $i < $len; $i++) {            // (hash << 5) + hash 相當於 hash * 33            //$hash = sprintf("%u", $hash * 33) + ord($s{$i});            //$hash = ($hash * 33 + ord($s{$i})) & 0x7FFFFFFF;            $hash = ($hash << $seed) + $hash + ord($s{$i});        }        return $hash & 0x7FFFFFFF;    }    /**     * 增加節點     * @param string $node 節點名稱     * @return object $this     */    public function addNode($node)    {        if (in_array($node, array_keys($this->nodes))) {            return;        }        for ($i = 1; $i <= $this->virtual; $i++) {            $key                  = $this->time33($node . '-' . $i);            $this->_ring[$key]    = $node;            $this->nodes[$node][] = $key;        }        ksort($this->_ring, SORT_NUMERIC);        return $this;    }    /**     * 擷取字串的HASH在圓環上面映射到的節點     * @param  string $key     * @return string $node     */    public function getNode($key)    {        $node = current($this->_ring);        $hash = $this->time33($key);        foreach ($this->_ring as $key => $value) {            if ($hash <= $key) {                $node = $value;                break;            }        }        return $node;    }    /**     * 擷取映射到特定節點的KEY     * 此方法需手動調用，非特殊情況不建議程式中使用此方法     * @param  string $node     * @param  string $keyPre     * @return mixed     */    public function getKey($node, $keyPre = ""){        if(!in_array($node, array_keys($this->nodes))){            return false;        }        $result = false;        for($i=1;$i<=10000;$i++){            $key = $keyPre . md5(rand(1000, 9999));            if($this->getNode($key) == $node){                $result = true;                break;            }        }        return $result ? $key : false;    }}$ch_obj = new ConsistentHashing();$ch_obj->addNode('node_1');$ch_obj->addNode('node_2');$ch_obj->addNode('node_3');$ch_obj->addNode('node_4');$ch_obj->addNode('node_5');$ch_obj->addNode('node_6');// +----------------------------------------------------------------------// | 查看key映射到的節點// +----------------------------------------------------------------------$key1 = "asofiwjamfdalksjfkasasdflasfja";$key2 = "jaksldfjlasfjsdjfioafaslkjflsadkjfl";$key3 = "asjldflkjasfsdjflkajkldsjfksajdlflajs";$key4 = "iowanfasijfmasdnfoas";$key5 = "pqkisndfhoalnfiewlkl";$key6 = "qjklasjdifoajfalsjflsa";echo sprintf("%-50s 映射到節點 %s\n", $key1, $ch_obj->getNode($key1));echo sprintf("%-50s 映射到節點 %s\n", $key2, $ch_obj->getNode($key2));echo sprintf("%-50s 映射到節點 %s\n", $key3, $ch_obj->getNode($key3));echo sprintf("%-50s 映射到節點 %s\n", $key4, $ch_obj->getNode($key4));echo sprintf("%-50s 映射到節點 %s\n", $key5, $ch_obj->getNode($key5));echo sprintf("%-50s 映射到節點 %s\n", $key6, $ch_obj->getNode($key6));// +----------------------------------------------------------------------// | 查看圓環和節點資訊// +----------------------------------------------------------------------// var_dump($ch_obj->getRing());// var_dump($ch_obj->nodes);// +----------------------------------------------------------------------// | 擷取特定節點的KEY// +----------------------------------------------------------------------// $key1 = $ch_obj->getKey('node_1', 'pre_');// var_dump($key1);// +----------------------------------------------------------------------// | 測試分布// +----------------------------------------------------------------------// $keys = array();// $rings = array();// for ($i = 1; $i <= 60000; $i++) {//     $key = sha1(rand(1000000,9999999));//     $node = $ch_obj->getNode($key);//     $rings[$node] = isset($rings[$node]) ? ++$rings[$node] : 1;// }// var_dump($rings);