PHP实现的服务器一致性hash分布算法示例

更新时间：2020-03-29 07:52:42 作者：startmvc

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：&l

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：