TwoLevels.php

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<?php
#require_once 'Zend/Cache/Backend/ExtendedInterface.php';

#require_once 'Zend/Cache/Backend.php';


class Zend_Cache_Backend_TwoLevels extends Zend_Cache_Backend implements Zend_Cache_Backend_ExtendedInterface
{
    protected $_options = array(
        'slow_backend' => 'File',
        'fast_backend' => 'Apc',
        'slow_backend_options' => array(),
        'fast_backend_options' => array(),
        'stats_update_factor' => 10,
        'slow_backend_custom_naming' => false,
        'fast_backend_custom_naming' => false,
        'slow_backend_autoload' => false,
        'fast_backend_autoload' => false,
        'auto_fill_fast_cache' => true,
        'auto_refresh_fast_cache' => true
    );

    protected $_slowBackend;

    protected $_fastBackend;

    protected $_fastBackendFillingPercentage = null;

    public function __construct(array $options = array())
    {
        parent::__construct($options);

        if ($this->_options['slow_backend'] === null) {
            Zend_Cache::throwException('slow_backend option has to set');
        } elseif ($this->_options['slow_backend'] instanceof Zend_Cache_Backend_ExtendedInterface) {
            $this->_slowBackend = $this->_options['slow_backend'];
        } else {
            $this->_slowBackend = Zend_Cache::_makeBackend(
                $this->_options['slow_backend'],
                $this->_options['slow_backend_options'],
                $this->_options['slow_backend_custom_naming'],
                $this->_options['slow_backend_autoload']
            );
            if (!in_array('Zend_Cache_Backend_ExtendedInterface', class_implements($this->_slowBackend))) {
                Zend_Cache::throwException('slow_backend must implement the Zend_Cache_Backend_ExtendedInterface interface');
            }
        }

        if ($this->_options['fast_backend'] === null) {
            Zend_Cache::throwException('fast_backend option has to set');
        } elseif ($this->_options['fast_backend'] instanceof Zend_Cache_Backend_ExtendedInterface) {
            $this->_fastBackend = $this->_options['fast_backend'];
        } else {
            $this->_fastBackend = Zend_Cache::_makeBackend(
                $this->_options['fast_backend'],
                $this->_options['fast_backend_options'],
                $this->_options['fast_backend_custom_naming'],
                $this->_options['fast_backend_autoload']
            );
            if (!in_array('Zend_Cache_Backend_ExtendedInterface', class_implements($this->_fastBackend))) {
                Zend_Cache::throwException('fast_backend must implement the Zend_Cache_Backend_ExtendedInterface interface');
            }
        }

        $this->_slowBackend->setDirectives($this->_directives);
        $this->_fastBackend->setDirectives($this->_directives);
    }

    public function test($id)
    {
        $fastTest = $this->_fastBackend->test($id);
        if ($fastTest) {
            return $fastTest;
        } else {
            return $this->_slowBackend->test($id);
        }
    }

    public function save($data, $id, $tags = array(), $specificLifetime = false, $priority = 8)
    {
        $usage = $this->_getFastFillingPercentage('saving');
        $boolFast = true;
        $lifetime = $this->getLifetime($specificLifetime);
        $preparedData = $this->_prepareData($data, $lifetime, $priority);
        if (($priority > 0) && (10 * $priority >= $usage)) {
            $fastLifetime = $this->_getFastLifetime($lifetime, $priority);
            $boolFast = $this->_fastBackend->save($preparedData, $id, array(), $fastLifetime);
            $boolSlow = $this->_slowBackend->save($preparedData, $id, $tags, $lifetime);
        } else {
            $boolSlow = $this->_slowBackend->save($preparedData, $id, $tags, $lifetime);
            if ($boolSlow === true) {
                $boolFast = $this->_fastBackend->remove($id);
                if (!$boolFast && !$this->_fastBackend->test($id)) {
                    // some backends return false on remove() even if the key never existed. (and it won't if fast is full)
                    // all we care about is that the key doesn't exist now
                    $boolFast = true;
                }
            }
        }

        return ($boolFast && $boolSlow);
    }

    public function load($id, $doNotTestCacheValidity = false)
    {
        $resultFast = $this->_fastBackend->load($id, $doNotTestCacheValidity);
        if ($resultFast === false) {
            $resultSlow = $this->_slowBackend->load($id, $doNotTestCacheValidity);
            if ($resultSlow === false) {
                // there is no cache at all for this id
                return false;
            }
        }
        $array = $resultFast !== false ? unserialize($resultFast) : unserialize($resultSlow);

        //In case no cache entry was found in the FastCache and auto-filling is enabled, copy data to FastCache
        if ($resultFast === false && $this->_options['auto_fill_fast_cache']) {
            $preparedData = $this->_prepareData($array['data'], $array['lifetime'], $array['priority']);
            $this->_fastBackend->save($preparedData, $id, array(), $array['lifetime']);
        }
        // maybe, we have to refresh the fast cache ?
        elseif ($this->_options['auto_refresh_fast_cache']) {
            if ($array['priority'] == 10) {
                // no need to refresh the fast cache with priority = 10
                return $array['data'];
            }
            $newFastLifetime = $this->_getFastLifetime($array['lifetime'], $array['priority'], time() - $array['expire']);
            // we have the time to refresh the fast cache
            $usage = $this->_getFastFillingPercentage('loading');
            if (($array['priority'] > 0) && (10 * $array['priority'] >= $usage)) {
                // we can refresh the fast cache
                $preparedData = $this->_prepareData($array['data'], $array['lifetime'], $array['priority']);
                $this->_fastBackend->save($preparedData, $id, array(), $newFastLifetime);
            }
        }
        return $array['data'];
    }

    public function remove($id)
    {
        $boolFast = $this->_fastBackend->remove($id);
        $boolSlow = $this->_slowBackend->remove($id);
        return $boolFast && $boolSlow;
    }

    public function clean($mode = Zend_Cache::CLEANING_MODE_ALL, $tags = array())
    {
        switch($mode) {
            case Zend_Cache::CLEANING_MODE_ALL:
                $boolFast = $this->_fastBackend->clean(Zend_Cache::CLEANING_MODE_ALL);
                $boolSlow = $this->_slowBackend->clean(Zend_Cache::CLEANING_MODE_ALL);
                return $boolFast && $boolSlow;
                break;
            case Zend_Cache::CLEANING_MODE_OLD:
                return $this->_slowBackend->clean(Zend_Cache::CLEANING_MODE_OLD);
            case Zend_Cache::CLEANING_MODE_MATCHING_TAG:
                $ids = $this->_slowBackend->getIdsMatchingTags($tags);
                $res = true;
                foreach ($ids as $id) {
                    $bool = $this->remove($id);
                    $res = $res && $bool;
                }
                return $res;
                break;
            case Zend_Cache::CLEANING_MODE_NOT_MATCHING_TAG:
                $ids = $this->_slowBackend->getIdsNotMatchingTags($tags);
                $res = true;
                foreach ($ids as $id) {
                    $bool = $this->remove($id);
                    $res = $res && $bool;
                }
                return $res;
                break;
            case Zend_Cache::CLEANING_MODE_MATCHING_ANY_TAG:
                $ids = $this->_slowBackend->getIdsMatchingAnyTags($tags);
                $res = true;
                foreach ($ids as $id) {
                    $bool = $this->remove($id);
                    $res = $res && $bool;
                }
                return $res;
                break;
            default:
                Zend_Cache::throwException('Invalid mode for clean() method');
                break;
        }
    }

    public function getIds()
    {
        return $this->_slowBackend->getIds();
    }

    public function getTags()
    {
        return $this->_slowBackend->getTags();
    }

    public function getIdsMatchingTags($tags = array())
    {
        return $this->_slowBackend->getIdsMatchingTags($tags);
    }

    public function getIdsNotMatchingTags($tags = array())
    {
        return $this->_slowBackend->getIdsNotMatchingTags($tags);
    }

    public function getIdsMatchingAnyTags($tags = array())
    {
        return $this->_slowBackend->getIdsMatchingAnyTags($tags);
    }

    public function getFillingPercentage()
    {
        return $this->_slowBackend->getFillingPercentage();
    }

    public function getMetadatas($id)
    {
        return $this->_slowBackend->getMetadatas($id);
    }

    public function touch($id, $extraLifetime)
    {
        return $this->_slowBackend->touch($id, $extraLifetime);
    }

    public function getCapabilities()
    {
        $slowBackendCapabilities = $this->_slowBackend->getCapabilities();
        return array(
            'automatic_cleaning' => $slowBackendCapabilities['automatic_cleaning'],
            'tags' => $slowBackendCapabilities['tags'],
            'expired_read' => $slowBackendCapabilities['expired_read'],
            'priority' => $slowBackendCapabilities['priority'],
            'infinite_lifetime' => $slowBackendCapabilities['infinite_lifetime'],
            'get_list' => $slowBackendCapabilities['get_list']
        );
    }

    private function _prepareData($data, $lifetime, $priority)
    {
        $lt = $lifetime;
        if ($lt === null) {
            $lt = 9999999999;
        }
        return serialize(array(
            'data' => $data,
            'lifetime' => $lifetime,
            'expire' => time() + $lt,
            'priority' => $priority
        ));
    }

    private function _getFastLifetime($lifetime, $priority, $maxLifetime = null)
    {
        if ($lifetime <= 0) {
            // if no lifetime, we have an infinite lifetime
            // we need to use arbitrary lifetimes
            $fastLifetime = (int) (2592000 / (11 - $priority));
        } else {
            // prevent computed infinite lifetime (0) by ceil
            $fastLifetime = (int) ceil($lifetime / (11 - $priority));
        }

        if ($maxLifetime >= 0 && $fastLifetime > $maxLifetime) {
            return $maxLifetime;
        }

        return $fastLifetime;
    }

    public function ___expire($id)
    {
        $this->_fastBackend->remove($id);
        $this->_slowBackend->___expire($id);
    }

    private function _getFastFillingPercentage($mode)
    {

        if ($mode == 'saving') {
            // mode saving
            if ($this->_fastBackendFillingPercentage === null) {
                $this->_fastBackendFillingPercentage = $this->_fastBackend->getFillingPercentage();
            } else {
                $rand = rand(1, $this->_options['stats_update_factor']);
                if ($rand == 1) {
                    // we force a refresh
                    $this->_fastBackendFillingPercentage = $this->_fastBackend->getFillingPercentage();
                }
            }
        } else {
            // mode loading
            // we compute the percentage only if it's not available in cache
            if ($this->_fastBackendFillingPercentage === null) {
                $this->_fastBackendFillingPercentage = $this->_fastBackend->getFillingPercentage();
            }
        }
        return $this->_fastBackendFillingPercentage;
    }

}