PHP 一致性hash实现
<?php
function mHash($key)
{
$md5 = substr(md5($key), 0, 8);
$seed = 31;
$hash = 0;
for($i = 0; $i < 8; $i++){
$hash = $hash * $seed + ord($md5{$i});
$i++;
}
return $hash & 0x7FFFFFFF;
}
class FlexiHash
{
private $serverList = array();
private $serverKeys = array();
private $isSorted = false;
function addServer($server)
{
$hash = mHash($server);
if (!isset($this->serverList[$hash])) {
$this->serverList[$hash] = $server;
}
$this->isSorted = false;
return true;
}
function removeServer($server)
{
$hash = mHash($server);
if (isset($this->serverList[$hash])) {
unset($this->serverList[$hash]);
}
$this->isSorted = false;
return true;
}
function lookup($key)
{
$hash = mHash($key);
if (!$this->isSorted) {
krsort($this->serverList, SORT_NUMERIC);
$this->isSorted = true;
$this->serverKeys = array_keys($this->serverList);
}
foreach ($this->serverList as $pos => $server) {
if ($hash >= $pos) return $server;
}
return $this->serverList[$this->serverKeys[count($this->serverList) - 1]];
}
}
$hserver = new FlexiHash();
$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');
$hserver->addServer('192.168.1.6');
echo "<pre>";
for($i=0; $i < 10000; $i++) {
$t = $hserver->lookup('key'.$i);
$arr[] = $t;
}
print_r($arr);