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<?php |
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/** |
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* Phossa Project |
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* |
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* PHP version 5.4 |
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* |
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* @category Library |
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* @package Phossa2\Cache |
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* @copyright Copyright (c) 2016 phossa.com |
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* @license http://mit-license.org/ MIT License |
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* @link http://www.phossa.com/ |
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*/ |
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/*# declare(strict_types=1); */ |
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namespace Phossa2\Cache\Extension; |
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use Phossa2\Cache\CacheItem; |
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use Phossa2\Cache\CachePool; |
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use Phossa2\Cache\Message\Message; |
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use Phossa2\Event\Interfaces\EventInterface; |
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use Phossa2\Event\EventableExtensionAbstract; |
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use Phossa2\Cache\Interfaces\CacheItemExtendedInterface; |
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/** |
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* Stampede protection for the cache |
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* |
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* If item expires in 600 seconds (configurable), and by 5% (configurable) |
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* chance, this extension will mark the $item as a miss to force regenerating |
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* the item before it is truly expired. |
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* |
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* ```php |
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* $stampede = new StampedeProtection([ |
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* 'probability' => 60, // probability 60/1000 |
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* 'time_left' => 300 // change time left in seconds |
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* ]); |
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* $cachePool->addExtension($stampede); |
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* ``` |
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* |
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* @package Phossa2\Cache |
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* @author Hong Zhang <[email protected]> |
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* @see EventableExtensionAbstract |
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* @see CacheItem |
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* @version 2.0.1 |
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* @since 2.0.0 added |
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* @since 2.0.1 moved to EventableExtensionAbstract |
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*/ |
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class StampedeProtection extends EventableExtensionAbstract |
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{ |
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/** |
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* Probability, usually 1 - 100 |
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* |
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* @var int |
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* @access protected |
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*/ |
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protected $probability = 50; |
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/** |
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* time left in seconds |
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* |
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* @var int |
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* @access protected |
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*/ |
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protected $time_left = 600; |
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/** |
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* {@inheritDoc} |
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*/ |
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public function methodsAvailable()/*# : array */ |
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{ |
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return ['stampedeProtect']; |
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} |
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/** |
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* {@inheritDoc} |
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*/ |
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protected function extensionHandles()/*# : array */ |
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{ |
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// change hit status |
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return [ |
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[ |
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'event' => CachePool::EVENT_HAS_AFTER, |
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'handler' => ['stampedeProtect', 80] |
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] |
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]; |
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} |
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/** |
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* Change hit status if ... |
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* |
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* @param EventInterface $event |
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* @return bool |
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* @access public |
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*/ |
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public function stampedeProtect(EventInterface $event)/*# : bool */ |
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{ |
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/* @var CachePool $pool */ |
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$pool = $event->getTarget(); |
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/* @var CacheItem $item */ |
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$item = $event->getParam('item'); |
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if ($item instanceof CacheItemExtendedInterface) { |
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$left = $item->getExpiration()->getTimestamp() - time(); |
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if ($left < $this->time_left && rand(1, 1000) <= $this->probability) { |
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return $pool->setError( |
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Message::get(Message::CACHE_EXT_STAMPEDE, $item->getKey()), |
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Message::CACHE_EXT_STAMPEDE |
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); |
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} |
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} |
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return true; |
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} |
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} |
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phossa2 /
libs
