PHP实现的一致性HASH算法示例

// +---------------------------------------------------------------------- // | Datetime: 2017-01-11 16:01:36 // +---------------------------------------------------------------------- // | Copyright: Perfect Is Shit // +---------------------------------------------------------------------- class ConsistentHashing { // 圆环 // hash -> 节点 private $_ring = array(); // 所有节点 // 节点 -> hash public $nodes = array(); // 每个节点的虚拟节点 public $virtual = 64; /** * 构造 * @param array $nodes 初始化的节点列表 */ public function __construct($nodes = array()) { if (!empty($nodes)) { foreach ($nodes as $value) { $this->addNode($value); } } } /** * 获取圆环内容 * @return array $this->_ring */ public function getRing() { return $this->_ring; } /** * time33 函数 * @param string $str * @return 32位正整数 * @author 大神们 */ public function time33($str) { // hash(i) = hash(i-1) * 33 + str[i] // $hash = 5381; ## 将hash设置为0，竟然比设置为5381分布效果更好！！！ $hash = 0; $s = md5($str); //相比其它版本，进行了md5加密 $seed = 5; $len = 32;//加密后长度32 for ($i = 0; $i < $len; $i++) { // (hash << 5) + hash 相当于 hash * 33 //$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; } /** * 增加节点 * @param string $node 节点名称 * @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; } /** * 获取字符串的HASH在圆环上面映射到的节点 * @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; } /** * 获取映射到特定节点的KEY * 此方法需手动调用，非特殊情况不建议程序中使用此方法 * @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映射到的节点 // +---------------------------------------------------------------------- $key1 = "asofiwjamfdalksjfkasasdflasfja"; $key2 = "jaksldfjlasfjsdjfioafaslkjflsadkjfl"; $key3 = "asjldflkjasfsdjflkajkldsjfksajdlflajs"; $key4 = "iowanfasijfmasdnfoas"; $key5 = "pqkisndfhoalnfiewlkl"; $key6 = "qjklasjdifoajfalsjflsa"; echo sprintf("%-50s 映射到节点 %s\n",$key1,$ch_obj->getNode($key1)); echo sprintf("%-50s 映射到节点 %s\n",$key2,$ch_obj->getNode($key2)); echo sprintf("%-50s 映射到节点 %s\n",$key3,$ch_obj->getNode($key3)); echo sprintf("%-50s 映射到节点 %s\n",$key4,$ch_obj->getNode($key4)); echo sprintf("%-50s 映射到节点 %s\n",$key5,$ch_obj->getNode($key5)); echo sprintf("%-50s 映射到节点 %s\n",$key6,$ch_obj->getNode($key6)); // +---------------------------------------------------------------------- // | 查看圆环和节点信息 // +---------------------------------------------------------------------- // var_dump($ch_obj->getRing()); // var_dump($ch_obj->nodes); // +---------------------------------------------------------------------- // | 获取特定节点的KEY // +---------------------------------------------------------------------- // $key1 = $ch_obj->getKey('node_1','pre_'); // var_dump($key1); // +---------------------------------------------------------------------- // | 测试分布 // +---------------------------------------------------------------------- // $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);