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