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PHP
/**
* 一致性hash分布式算法
* @param $key
* @return int
* 实现步骤
* 1.先将0~ 是32位最大带符号整数（0x7FFFFFFF） 想象成一个闭环
* 2.将服务器列表通过hash算法分布在 圆环之中
* 3.将key值也分布在圆环之中
* 4.通过_isSorted判断服务器是否需要进行倒序排序 排序后遍历服务器 找到最近的服务器 返回
* hash算法是不保证平衡的 为了尽量保证平衡性 我们应该加入虚拟节点数 将一个服务器节点虚拟化成为多个 较大程度上保证了平衡性
*/
class FlexiHash{
private $_serverList = array();
private $_isSorted = false;
private $_virtual_node_num = 20;//虚拟节点数 服务器越少
增加的虚拟节点数应该越多
//通过hash算法返回一个整数值
protected function myHash($key){
$md5 = substr(md5($key),8);
$seed = 31; //种子值
$hash=0;
for($i=0;$i<8;$i++){
$hash = $hash*$seed+ord($md5{$i}); //ord 返回ascii值
$i++;
}
return $hash&0x7FFFFFFF; //0x7FFFFFFF表示最大值
}
//添加服务器
function addServer($server){
$hash =$this->myHash($server. '#1');
if(!isset($this->_serverList[$hash])) {
for ($i = 1; $i <= $this->_virtual_node_num; $i++) {
$hash = $this->myHash($server . '#' . $i);
$this->_serverList[$hash] = $server;
}
}
$this->_isSorted = false;
return true;
}
//
删除服务器
function removeServer($server){
for ($i = 1; $i <= $this->_virtual_node_num; $i++) {
$hash = $this->myHash($server . '#' . $i);
unset($this->_serverList[$hash]);
}
$this->_isSorted = false;
return true;
}
//
获取服务器
function lookup($key){
$hash =$this->myHash($key);
if(!$this->_isSorted){
krsort($this->_serverList,SORT_NUMERIC);
$this->_isSorted = true;
}
foreach($this->_serverList as $pos=>$server){
if($hash >= $pos) return $server;
}
return end($this->_serverList);
}
public function getServerList(){
krsort($this->_serverList,SORT_NUMERIC);
return $this->_serverList;
}
}
//demo test
$hserver = new FlexiHash();
//
添加服务器
$hserver->addServer('192.168.1.1');
$hserver->addServer('192.168.1.2');
$hserver->addServer('192.168.1.3');
$hserver->addServer('192.168.1.4');
$hserver->addServer('192.168.1.5');
$key1='Key1111';
$key2='Key2222';
$key2='Key3333';
$key2='Key4444';
$key2='Key5555';
$key2='Key6666';
echo "save key1 in server: ".$hserver->lookup($key1).
PHP_EOL;
echo "save key2 in server: ".$hserver->lookup($key2).
PHP_EOL;
echo "save key1 in server: ".$hserver->lookup($key3).
PHP_EOL;
echo "save key2 in server: ".$hserver->lookup($key4).
PHP_EOL;
echo "save key1 in server: ".$hserver->lookup($key5).
PHP_EOL;
echo "save key2 in server: ".$hserver->lookup($key6).
PHP_EOL;
echo "================================================".
PHP_EOL;
//移除服务器 key值将
自动转义到下一台服务器
$hserver->removeServer('192.168.1.4');
echo "save key1 in server: ".$hserver->lookup($key1).
PHP_EOL;
echo "save key2 in server: ".$hserver->lookup($key2).
PHP_EOL;
echo "save key1 in server: ".$hserver->lookup($key3).
PHP_EOL;
echo "save key2 in server: ".$hserver->lookup($key4).
PHP_EOL;
echo "save key1 in server: ".$hserver->lookup($key5).
PHP_EOL;
echo "save key2 in server: ".$hserver->lookup($key6).
PHP_EOL;
echo "================================================".
PHP_EOL;
//恢复故障服务器 key值将恢复原来服务器
$hserver->addServer('192.168.1.4');
echo "save key1 in server: ".$hserver->lookup($key1).
PHP_EOL;
echo "save key2 in server: ".$hserver->lookup($key2).
PHP_EOL;
echo "save key1 in server: ".$hserver->lookup($key3).
PHP_EOL;
echo "save key2 in server: ".$hserver->lookup($key4).
PHP_EOL;
echo "save key1 in server: ".$hserver->lookup($key5).
PHP_EOL;
echo "save key2 in server: ".$hserver->lookup($key6).
PHP_EOL;
