PHP实现的服务器一致性hash分布算法示例

本文实例讲述了PHP实现的服务器一致性hash分布算法。分享给大家供大家参考，具体如下：

<?php
/**
* 对服务器进行一致性hash分布算法
*/
class HashRing
{
 private $servers = array();
 private $nodeList = array();
 private $nodeHashList = array();
 private $nodeTotalNum = 0;
 private $virtualNodeNum = 32;
 private $keyHash = '';
 public function __construct($servers)
 {
   $this->servers = $servers;
   foreach ($servers as $server) {
     for ($i = 0; $i < $this->virtualNodeNum; $i++) {
       $this->nodeList[sprintf("％u", crc32($server.'-'.$i))] = array($server, $i);
     }
   }
   ksort($this->nodeList);
   $this->nodeHashList = array_keys($this->nodeList);
 }
 private function getNodeIndex($key)
 {
   $this->keyHash = sprintf("％u", crc32($key));
   if ($this->keyHash > end($this->nodeHashList)) {
     $this->keyHash = $this->keyHash ％ end($this->nodeHashList);
   }
   if ($this->keyHash <= reset($this->nodeHashList)) {
     return 0;
   }
   $this->nodeTotalNum = count($this->nodeHashList);
   return $this->binaryChopIndex(0, $this->nodeTotalNum);
 }
 private function binaryChopIndex($l=0, $r=0)
 {
   if ($l < $r) {
     $avg = intval(($l+$r) / 2);
     if ($this->nodeHashList[$avg] == $this->keyHash) {
       return $avg;
     } elseif ($this->keyHash < $this->nodeHashList[$avg] && ($avg > 0)) {
       return $this->binaryChopIndex($l, $avg-1);
     } else {
       return $this->binaryChopIndex($avg+1, $r);
     }
   } else {
     return $l;
   }
 }
 public function getServersByKey($key, $num=1)
 {
   $index = $this->getNodeIndex($key);
   $server = $this->nodeList[$this->nodeHashList[$index]];
   if ($num == 1) {
     return $server[0];
   }
   if ($num >= count($this->servers)) {
     $num = count($this->servers);
   }
   $result = array($server[0]);
   for ($i=$index+1; true; $i++) {
     if ($i >= $this->nodeTotalNum) {
       $i = 0;
     }
     $nextServer = $this->nodeList[$this->nodeHashList[$i]];
     if (!in_array($nextServer[0], $result)) {
       $result[] = $nextServer[0];
     }
     if (count($result) == $num) {
       break;
     }
   }
   return $result;
 }
}
//示例
$servers = 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'
);
$obj = new HashRing($servers);
$servers = $obj->getServersByKey('testkey', 2);
print_r($servers);
echo "\n";

运行结果：

Array
(
    [0] => 127.0.0.1:11214
    [1] => 127.0.0.1:11211
)

希望本文所述对大家PHP程序设计有所帮助。

来源：https://blog.csdn.net/flynetcn/article/details/46820373