Viewing file:  KetamaRing.php (1.85 KB) -rw-r--r--
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<?php
/*
* This file is part of the Predis package.
*
* (c) 2009-2020 Daniele Alessandri
* (c) 2021-2025 Till Krüss
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*/
namespace Predis\Cluster\Distributor;
/**
* This class implements an hashring-based distributor that uses the same
* algorithm of libketama to distribute keys in a cluster using client-side
* sharding.
* @author Lorenzo Castelli <lcastelli@gmail.com>
*/
class KetamaRing extends HashRing
{
public const DEFAULT_REPLICAS = 160;
/**
* @param mixed $nodeHashCallback Callback returning a string used to calculate the hash of nodes.
*/
public function __construct($nodeHashCallback = null)
{
parent::__construct($this::DEFAULT_REPLICAS, $nodeHashCallback);
}
/**
* {@inheritdoc}
*/
protected function addNodeToRing(&$ring, $node, $totalNodes, $replicas, $weightRatio)
{
$nodeObject = $node['object'];
$nodeHash = $this->getNodeHash($nodeObject);
$replicas = (int) floor($weightRatio * $totalNodes * ($replicas / 4));
for ($i = 0; $i < $replicas; ++$i) {
$unpackedDigest = unpack('V4', md5("$nodeHash-$i", true));
foreach ($unpackedDigest as $key) {
$ring[$key] = $nodeObject;
}
}
}
/**
* {@inheritdoc}
*/
public function hash($value)
{
$hash = unpack('V', md5($value, true));
return $hash[1];
}
/**
* {@inheritdoc}
*/
protected function wrapAroundStrategy($upper, $lower, $ringKeysCount)
{
// Binary search for the first item in ringkeys with a value greater
// or equal to the key. If no such item exists, return the first item.
return $lower < $ringKeysCount ? $lower : 0;
}
}
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