c58f935fdc
The example (and related documentation at redis.io) was not updated for 5 years. Redis had no sorted sets and hashes when the original code was written (!). An update was really needed. We also use a modern PHP client now: Predis. A copy is shipped within this repository to make life easier to newcomers trying Redis for the first time via this example.
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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