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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\CachePool; |
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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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* DistributedExpiration |
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* |
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* Change expiration time by -5% to 5% to evenly distribute cache miss |
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* |
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* ```php |
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* $ext = new DistributedExpiration([ |
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* 'distribution' => 30 // -3% to 3% |
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* ]); |
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* |
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* // enable this ext |
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* $cachePool->addExtension($ext); |
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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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* @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 DistributedExpiration extends EventableExtensionAbstract |
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{ |
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/** |
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* item expiration time distribution 5% (50/1000) |
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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 $distribution = 50; |
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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 ['distributeExpire']; |
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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 item expire before save or saveDeferred |
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return [ |
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[ |
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'event' => CachePool::EVENT_SAVE_BEFORE, |
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'handler' => ['distributeExpire', 80] |
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], |
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[ |
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'event' => CachePool::EVENT_DEFER_BEFORE, |
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'handler' => ['distributeExpire', 80] |
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] |
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]; |
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} |
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/** |
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* Evenly distribute the expiration time |
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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 distributeExpire(EventInterface $event)/*# : bool */ |
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{ |
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$dist = $this->distribution; |
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$item = $event->getParam('item'); |
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if ($item instanceof CacheItemExtendedInterface) { |
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// expire ttl |
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$ttl = $item->getExpiration()->getTimestamp() - time(); |
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// percentage |
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$percent = (rand(0, $dist * 2) - $dist) * 0.001; |
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// new expire ttl |
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$new_ttl = (int) round($ttl + $ttl * $percent); |
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$item->expiresAfter($new_ttl); |
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} |
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return true; |
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} |
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} |
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phossa2 /
libs
