<?php/** * 對服務器進行一致性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";