Proyectos de Subversion Moodle

<?php

// This file is part of Moodle - http://moodle.org/

//

// Moodle is free software: you can redistribute it and/or modify

// it under the terms of the GNU General Public License as published by

// the Free Software Foundation, either version 3 of the License, or

// (at your option) any later version.

//

// Moodle is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

// GNU General Public License for more details.

//

// You should have received a copy of the GNU General Public License

// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

namespace core_cache;

use core\exception\coding_exception;

/**

 * A session cache.

 *

 * This class is used for session caches returned by the cache::make methods.

 *

 * It differs from the application loader in a couple of noteable ways:

 *    1. Sessions are always expected to exist.

 *       Because of this we don't ever use the static acceleration array.

 *    2. Session data for a loader instance (store + definition) is consolidate into a

 *       single array for storage within the store.

 *       Along with this we embed a lastaccessed time with the data. This way we can

 *       check sessions for a last access time.

 *    3. Session stores are required to support key searching and must

 *       implement searchable_cache_interface. This ensures stores used for the cache can be

 *       targetted for garbage collection of session data.

 *

 * This cache class should never be interacted with directly. Instead you should always use the cache::make methods.

 * It is technically possible to call those methods through this class however there is no guarantee that you will get an

 * instance of this class back again.

 *

 * @todo we should support locking in the session as well. Should be pretty simple to set up.

 *

 * @internal don't use me directly.

 * @method store|searchable_cache_interface get_store() Returns the cache store which must implement

 *                                                      both searchable_cache_interface.

 *

 * @package    core_cache

 * @category   cache

 * @copyright  2012 Sam Hemelryk

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

class session_cache extends cache {

    /**

     * The user the session has been established for.

     * @var int

     */

    protected static $loadeduserid = null;

    /**

     * The userid this cache is currently using.

     * @var int

     */

    protected $currentuserid = null;

    /**

     * The session id we are currently using.

     * @var array

     */

    protected $sessionid = null;

    /**

     * The session data for the above session id.

     * @var array

     */

    protected $session = null;

    /**

     * Constant used to prefix keys.

     */

    const KEY_PREFIX = 'sess_';

    /**

     * This is the key used to track last access.

     */

    const LASTACCESS = '__lastaccess__';

    /**

     * Override the cache::construct method.

     *

     * This function gets overriden so that we can process any invalidation events if need be.

     * If the definition doesn't have any invalidation events then this occurs exactly as it would for the cache class.

     * Otherwise we look at the last invalidation time and then check the invalidation data for events that have occured

     * between then now.

     *

     * You should not call this method from your code, instead you should use the cache::make methods.

     *

     * @param definition $definition

     * @param store $store

     * @param loader_interface|data_source_interface $loader

     */

    public function __construct(definition $definition, store $store, $loader = null) {

        // First up copy the loadeduserid to the current user id.

        $this->currentuserid = self::$loadeduserid;

        $this->set_session_id();

        parent::__construct($definition, $store, $loader);

        // This will trigger check tracked user. If this gets removed a call to that will need to be added here in its place.

        $this->set(self::LASTACCESS, cache::now());

        $this->handle_invalidation_events();

    }

    /**

     * Sets the session id for the loader.

     */

    protected function set_session_id() {

        $this->sessionid = preg_replace('#[^a-zA-Z0-9_]#', '_', session_id());

    }

    /**

     * Returns the prefix used for all keys.

     * @return string

     */

    protected function get_key_prefix() {

        return 'u' . $this->currentuserid . '_' . $this->sessionid;

    }

    /**

     * Parses the key turning it into a string (or array is required) suitable to be passed to the cache store.

     *

     * This function is called for every operation that uses keys. For this reason we use this function to also check

     * that the current user is the same as the user who last used this cache.

     *

     * On top of that if prepends the string 'sess_' to the start of all keys. The _ ensures things are easily identifiable.

     *

     * @param string|int $key As passed to get|set|delete etc.

     * @return string|array String unless the store supports multi-identifiers in which case an array if returned.

     */

    protected function parse_key($key) {

        $prefix = $this->get_key_prefix();

        if ($key === self::LASTACCESS) {

            return $key . $prefix;

        }

        return $prefix . '_' . parent::parse_key($key);

    }

    /**

     * Check that this cache instance is tracking the current user.

     */

    protected function check_tracked_user() {

        if (isset($_SESSION['USER']->id) && $_SESSION['USER']->id !== null) {

            // Get the id of the current user.

            $new = $_SESSION['USER']->id;

        } else {

            // No user set up yet.

            $new = 0;

        }

        if ($new !== self::$loadeduserid) {

            // The current user doesn't match the tracked userid for this request.

            if (!is_null(self::$loadeduserid)) {

                // Purge the data we have for the old user.

                // This way we don't bloat the session.

                $this->purge();

            }

            self::$loadeduserid = $new;

            $this->currentuserid = $new;

        } else if ($new !== $this->currentuserid) {

            // The current user matches the loaded user but not the user last used by this cache.

            $this->purge_current_user();

            $this->currentuserid = $new;

        }

    }

    /**

     * Purges the session cache of all data belonging to the current user.

     */

    public function purge_current_user() {

        $keys = $this->get_store()->find_by_prefix($this->get_key_prefix());

        $this->get_store()->delete_many($keys);

    }

    /**

     * Retrieves the value for the given key from the cache.

     *

     * @param string|int $key The key for the data being requested.

     *      It can be any structure although using a scalar string or int is recommended in the interests of performance.

     *      In advanced cases an array may be useful such as in situations requiring the multi-key functionality.

     * @param int $requiredversion Minimum required version of the data or cache::VERSION_NONE

     * @param int $strictness One of IGNORE_MISSING | MUST_EXIST

     * @param mixed &$actualversion If specified, will be set to the actual version number retrieved

     * @return mixed|false The data from the cache or false if the key did not exist within the cache.

     * @throws coding_exception

     */

    protected function get_implementation($key, int $requiredversion, int $strictness, &$actualversion = null) {

        // Check the tracked user.

        $this->check_tracked_user();

        // Use parent code.

        return parent::get_implementation($key, $requiredversion, $strictness, $actualversion);

    }

    /**

     * Sends a key => value pair to the cache.

     *

     * <code>

     * // This code will add four entries to the cache, one for each url.

     * $cache->set('main', 'http://moodle.org');

     * $cache->set('docs', 'http://docs.moodle.org');

     * $cache->set('tracker', 'http://tracker.moodle.org');

     * $cache->set('qa', 'http://qa.moodle.net');

     * </code>

     *

     * @param string|int $key The key for the data being requested.

     *      It can be any structure although using a scalar string or int is recommended in the interests of performance.

     *      In advanced cases an array may be useful such as in situations requiring the multi-key functionality.

     * @param mixed $data The data to set against the key.

     * @return bool True on success, false otherwise.

     */

    public function set($key, $data) {

        $this->check_tracked_user();

        $loader = $this->get_loader();

        if ($loader !== false) {

            // We have a loader available set it there as well.

            // We have to let the loader do its own parsing of data as it may be unique.

            $loader->set($key, $data);

        }

        if (is_object($data) && $data instanceof cacheable_object_interface) {

            $data = new cached_object($data);

        } else if (!$this->get_store()->supports_dereferencing_objects() && !is_scalar($data)) {

            // If data is an object it will be a reference.

            // If data is an array if may contain references.

            // We want to break references so that the cache cannot be modified outside of itself.

            // Call the function to unreference it (in the best way possible).

            $data = $this->unref($data);

        }

        // We dont' support native TTL here as we consolidate data for sessions.

        if ($this->has_a_ttl() && !$this->store_supports_native_ttl()) {

            $data = new ttl_wrapper($data, $this->get_definition()->get_ttl());

        }

        $success = $this->get_store()->set($this->parse_key($key), $data);

        if ($this->perfdebug) {

            helper::record_cache_set(

                $this->get_store(),

                $this->get_definition(),

                1,

                $this->get_store()->get_last_io_bytes()

            );

        }

        return $success;

    }

    /**

     * Delete the given key from the cache.

     *

     * @param string|int $key The key to delete.

     * @param bool $recurse When set to true the key will also be deleted from all stacked cache loaders and their stores.

     *     This happens by default and ensure that all the caches are consistent. It is NOT recommended to change this.

     * @return bool True of success, false otherwise.

     */

    public function delete($key, $recurse = true) {

        $parsedkey = $this->parse_key($key);

        if ($recurse && $this->get_loader() !== false) {

            // Delete from the bottom of the stack first.

            $this->get_loader()->delete($key, $recurse);

        }

        return $this->get_store()->delete($parsedkey);

    }

    /**

     * Retrieves an array of values for an array of keys.

     *

     * Using this function comes with potential performance implications.

     * Not all cache stores will support get_many/set_many operations and in order to replicate this functionality will call

     * the equivalent singular method for each item provided.

     * This should not deter you from using this function as there is a performance benefit in situations where the cache store

     * does support it, but you should be aware of this fact.

     *

     * @param array $keys The keys of the data being requested.

     *      Each key can be any structure although using a scalar string or int is recommended in the interests of performance.

     *      In advanced cases an array may be useful such as in situations requiring the multi-key functionality.

     * @param int $strictness One of IGNORE_MISSING or MUST_EXIST.

     * @return array An array of key value pairs for the items that could be retrieved from the cache.

     *      If MUST_EXIST was used and not all keys existed within the cache then an exception will be thrown.

     *      Otherwise any key that did not exist will have a data value of false within the results.

     * @throws coding_exception

     */

    public function get_many(array $keys, $strictness = IGNORE_MISSING) {

        $this->check_tracked_user();

        $parsedkeys = [];

        $keymap = [];

        foreach ($keys as $key) {

            $parsedkey = $this->parse_key($key);

            $parsedkeys[$key] = $parsedkey;

            $keymap[$parsedkey] = $key;

        }

        $result = $this->get_store()->get_many($parsedkeys);

        if ($this->perfdebug) {

            $readbytes = $this->get_store()->get_last_io_bytes();

        }

        $return = [];

        $missingkeys = [];

        $hasmissingkeys = false;

        foreach ($result as $parsedkey => $value) {

            $key = $keymap[$parsedkey];

            if ($value instanceof ttl_wrapper) {

                /* @var ttl_wrapper $value */

                if ($value->has_expired()) {

                    $this->delete($keymap[$parsedkey]);

                    $value = false;

                } else {

                    $value = $value->data;

                }

            }

            if ($value instanceof cached_object) {

                /* @var cached_object $value */

                $value = $value->restore_object();

            } else if (!$this->get_store()->supports_dereferencing_objects() && !is_scalar($value)) {

                // If data is an object it will be a reference.

                // If data is an array if may contain references.

                // We want to break references so that the cache cannot be modified outside of itself.

                // Call the function to unreference it (in the best way possible).

                $value = $this->unref($value);

            }

            $return[$key] = $value;

            if ($value === false) {

                $hasmissingkeys = true;

                $missingkeys[$parsedkey] = $key;

            }

        }

        if ($hasmissingkeys) {

            // We've got missing keys - we've got to check any loaders or data sources.

            $loader = $this->get_loader();

            $datasource = $this->get_datasource();

            if ($loader !== false) {

                foreach ($loader->get_many($missingkeys) as $key => $value) {

                    if ($value !== false) {

                        $return[$key] = $value;

                        unset($missingkeys[$parsedkeys[$key]]);

                    }

                }

            }

            $hasmissingkeys = count($missingkeys) > 0;

            if ($datasource !== false && $hasmissingkeys) {

                // We're still missing keys but we've got a datasource.

                foreach ($datasource->load_many_for_cache($missingkeys) as $key => $value) {

                    if ($value !== false) {

                        $return[$key] = $value;

                        unset($missingkeys[$parsedkeys[$key]]);

                    }

                }

                $hasmissingkeys = count($missingkeys) > 0;

            }

        }

        if ($hasmissingkeys && $strictness === MUST_EXIST) {

            throw new coding_exception('Requested key did not exist in any cache stores and could not be loaded.');

        }

        if ($this->perfdebug) {

            $hits = 0;

            $misses = 0;

            foreach ($return as $value) {

                if ($value === false) {

                    $misses++;

                } else {

                    $hits++;

                }

            }

            helper::record_cache_hit($this->get_store(), $this->get_definition(), $hits, $readbytes);

            helper::record_cache_miss($this->get_store(), $this->get_definition(), $misses);

        }

        return $return;

    }

    /**

     * Delete all of the given keys from the cache.

     *

     * @param array $keys The key to delete.

     * @param bool $recurse When set to true the key will also be deleted from all stacked cache loaders and their stores.

     *     This happens by default and ensure that all the caches are consistent. It is NOT recommended to change this.

     * @return int The number of items successfully deleted.

     */

    public function delete_many(array $keys, $recurse = true) {

        $parsedkeys = array_map([$this, 'parse_key'], $keys);

        if ($recurse && $this->get_loader() !== false) {

            // Delete from the bottom of the stack first.

            $this->get_loader()->delete_many($keys, $recurse);

        }

        return $this->get_store()->delete_many($parsedkeys);

    }

    /**

     * Sends several key => value pairs to the cache.

     *

     * Using this function comes with potential performance implications.

     * Not all cache stores will support get_many/set_many operations and in order to replicate this functionality will call

     * the equivalent singular method for each item provided.

     * This should not deter you from using this function as there is a performance benefit in situations where the cache store

     * does support it, but you should be aware of this fact.

     *

     * <code>

     * // This code will add four entries to the cache, one for each url.

     * $cache->set_many(array(

     *     'main' => 'http://moodle.org',

     *     'docs' => 'http://docs.moodle.org',

     *     'tracker' => 'http://tracker.moodle.org',

     *     'qa' => ''http://qa.moodle.net'

     * ));

     * </code>

     *

     * @param array $keyvaluearray An array of key => value pairs to send to the cache.

     * @return int The number of items successfully set. It is up to the developer to check this matches the number of items.

     *      ... if they care that is.

     */

    public function set_many(array $keyvaluearray) {

        $this->check_tracked_user();

        $loader = $this->get_loader();

        if ($loader !== false) {

            // We have a loader available set it there as well.

            // We have to let the loader do its own parsing of data as it may be unique.

            $loader->set_many($keyvaluearray);

        }

        $data = [];

        $definitionid = $this->get_definition()->get_ttl();

        $simulatettl = $this->has_a_ttl() && !$this->store_supports_native_ttl();

        foreach ($keyvaluearray as $key => $value) {

            if (is_object($value) && $value instanceof cacheable_object_interface) {

                $value = new cached_object($value);

            } else if (!$this->get_store()->supports_dereferencing_objects() && !is_scalar($value)) {

                // If data is an object it will be a reference.

                // If data is an array if may contain references.

                // We want to break references so that the cache cannot be modified outside of itself.

                // Call the function to unreference it (in the best way possible).

                $value = $this->unref($value);

            }

            if ($simulatettl) {

                $value = new ttl_wrapper($value, $definitionid);

            }

            $data[$key] = [

                'key' => $this->parse_key($key),

                'value' => $value,

            ];

        }

        $successfullyset = $this->get_store()->set_many($data);

        if ($this->perfdebug && $successfullyset) {

            helper::record_cache_set(

                $this->get_store(),

                $this->get_definition(),

                $successfullyset,

                $this->get_store()->get_last_io_bytes()

            );

        }

        return $successfullyset;

    }

    /**

     * Purges the cache store, and loader if there is one.

     *

     * @return bool True on success, false otherwise

     */

    public function purge() {

        $this->get_store()->purge();

        if ($this->get_loader()) {

            $this->get_loader()->purge();

        }

        return true;

    }

    /**

     * Test is a cache has a key.

     *

     * The use of the has methods is strongly discouraged. In a high load environment the cache may well change between the

     * test and any subsequent action (get, set, delete etc).

     * Instead it is recommended to write your code in such a way they it performs the following steps:

     * <ol>

     * <li>Attempt to retrieve the information.</li>

     * <li>Generate the information.</li>

     * <li>Attempt to set the information</li>

     * </ol>

     *

     * Its also worth mentioning that not all stores support key tests.

     * For stores that don't support key tests this functionality is mimicked by using the equivalent get method.

     * Just one more reason you should not use these methods unless you have a very good reason to do so.

     *

     * @param string|int $key

     * @param bool $tryloadifpossible If set to true, the cache doesn't contain the key, and there is another cache loader or

     *      data source then the code will try load the key value from the next item in the chain.

     * @return bool True if the cache has the requested key, false otherwise.

     */

    public function has($key, $tryloadifpossible = false) {

        $this->check_tracked_user();

        $parsedkey = $this->parse_key($key);

        $store = $this->get_store();

        if ($this->has_a_ttl() && !$this->store_supports_native_ttl()) {

            // The data has a TTL and the store doesn't support it natively.

            // We must fetch the data and expect a ttl wrapper.

            $data = $store->get($parsedkey);

            $has = ($data instanceof ttl_wrapper && !$data->has_expired());

        } else if (!$this->store_supports_key_awareness()) {

            // The store doesn't support key awareness, get the data and check it manually... puke.

            // Either no TTL is set of the store supports its handling natively.

            $data = $store->get($parsedkey);

            $has = ($data !== false);

        } else {

            // The store supports key awareness, this is easy!

            // Either no TTL is set of the store supports its handling natively.

            /* @var store|key_aware_cache_interface $store */

            $has = $store->has($parsedkey);

        }

        if (!$has && $tryloadifpossible) {

            $result = null;

            if ($this->get_loader() !== false) {

                $result = $this->get_loader()->get($parsedkey);

            } else if ($this->get_datasource() !== null) {

                $result = $this->get_datasource()->load_for_cache($key);

            }

            $has = ($result !== null);

            if ($has) {

                $this->set($key, $result);

            }

        }

        return $has;

    }

    /**

     * Test is a cache has all of the given keys.

     *

     * It is strongly recommended to avoid the use of this function if not absolutely required.

     * In a high load environment the cache may well change between the test and any subsequent action (get, set, delete etc).

     *

     * Its also worth mentioning that not all stores support key tests.

     * For stores that don't support key tests this functionality is mimicked by using the equivalent get method.

     * Just one more reason you should not use these methods unless you have a very good reason to do so.

     *

     * @param array $keys

     * @return bool True if the cache has all of the given keys, false otherwise.

     */

    public function has_all(array $keys) {

        $this->check_tracked_user();

        if (($this->has_a_ttl() && !$this->store_supports_native_ttl()) || !$this->store_supports_key_awareness()) {

            foreach ($keys as $key) {

                if (!$this->has($key)) {

                    return false;

                }

            }

            return true;

        }

        // The cache must be key aware and if support native ttl if it a ttl is set.

        /* @var store|key_aware_cache_interface $store */

        $store = $this->get_store();

        return $store->has_all(array_map([$this, 'parse_key'], $keys));

    }

    /**

     * Test if a cache has at least one of the given keys.

     *

     * It is strongly recommended to avoid the use of this function if not absolutely required.

     * In a high load environment the cache may well change between the test and any subsequent action (get, set, delete etc).

     *

     * Its also worth mentioning that not all stores support key tests.

     * For stores that don't support key tests this functionality is mimicked by using the equivalent get method.

     * Just one more reason you should not use these methods unless you have a very good reason to do so.

     *

     * @param array $keys

     * @return bool True if the cache has at least one of the given keys

     */

    public function has_any(array $keys) {

        if (($this->has_a_ttl() && !$this->store_supports_native_ttl()) || !$this->store_supports_key_awareness()) {

            foreach ($keys as $key) {

                if ($this->has($key)) {

                    return true;

                }

            }

            return false;

        }

        /* @var store|key_aware_cache_interface $store */

        $store = $this->get_store();

        return $store->has_any(array_map([$this, 'parse_key'], $keys));

    }

    /**

     * The session loader never uses static acceleration.

     * Instead it stores things in the static $session variable. Shared between all session loaders.

     *

     * @return bool

     */

    protected function use_static_acceleration() {

        return false;

    }

}

// Alias this class to the old name.

// This file will be autoloaded by the legacyclasses autoload system.

// In future all uses of this class will be corrected and the legacy references will be removed.

class_alias(session_cache::class, \cache_session::class);