PHP实现一致性HASH算法实现步骤解析
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- 2018-05-17 15:43:301563浏览
这次给大家带来PHP实现一致性HASH算法实现步骤解析，PHP实现一致性HASH算法实现的注意事项有哪些，下面就是实战案例，一起来看一下。
<?php
// +----------------------------------------------------------------------
// | Perfect Is Shit
// +----------------------------------------------------------------------
// | PHP实现：一致性HASH算法
// +----------------------------------------------------------------------
// | Author: alexander <gt199899@gmail.com>
// +----------------------------------------------------------------------
// | 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);
运行结果：
asofiwjamfdalksjfkasasdflasfja 映射到节点 node_1 jaksldfjlasfjsdjfioafaslkjflsadkjfl 映射到节点 node_2 asjldflkjasfsdjflkajkldsjfksajdlflajs 映射到节点 node_1 iowanfasijfmasdnfoas 映射到节点 node_2 pqkisndfhoalnfiewlkl 映射到节点 node_3 qjklasjdifoajfalsjflsa 映射到节点 node_5
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