基于php的一个最简略的memcache的分布式算法

首先，核心函数是这个

function mHash($key){

$md=substr(md5($key),0,8);

$seed=31;

$hash=0;

for($i=0;$i<8;$i++){

$hash=$hash*$seed+ord($md5{$i});

}

return $hash & 0x7FFFFFFF;

}

class HashServer{

private $serverlist;

private $issorted=false;

function addServer($server){

$hash=mHash($server);

if(!isset($this->serverlist[$hash])){

$this->serverlist[$hash]=$server;

}

return true;

}

function getKeyServer($key){

$hash=mHash($key);

if(!this->issorted){

ksort($this->serverlist,SORT_NUMERIC);

}

foreach($this->serverlist as $k=>$v){

if($hash>=$k) return $v;
}

return $this->serverlist[count($this->serverlist)-1];

}

}

//下面开始测试

$hs=new HashServer();

$hs->addServer('192.168.1.1');

$hs->addServer('192.168.1.2');

$hs->addServer('192.168.1.3');

echo $hs->getKeyServer('key1');

echo $hs->getKeyServer('key2');

echo $hs->getKeyServer('key3');