Search moodle.org's
Developer Documentation

See Release Notes
Long Term Support Release

  • Bug fixes for general core bugs in 3.9.x will end* 10 May 2021 (12 months).
  • Bug fixes for security issues in 3.9.x will end* 8 May 2023 (36 months).
  • PHP version: minimum PHP 7.2.0 Note: minimum PHP version has increased since Moodle 3.8. PHP 7.3.x and 7.4.x are supported too.
<?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/>.

/**
 * Cache API interfaces
 *
 * This file is part of Moodle's cache API, affectionately called MUC.
 * It contains the components that are requried in order to use caching.
 *
 * @package    core
 * @category   cache
 * @copyright  2012 Sam Hemelryk
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

defined('MOODLE_INTERNAL') || die();

/**
 * Cache Loader.
 *
 * This cache loader interface provides the required structure for classes that wish to be interacted with as a
 * means of accessing and interacting with a cache.
 *
 * Can be implemented by any class wishing to be a cache loader.
 */
interface cache_loader {

    /**
     * Retrieves the value for the given key from the cache.
     *
     * @param string|int $key The key for the data being requested.
     * @param int $strictness One of IGNORE_MISSING or MUST_EXIST.
     * @return mixed The data retrieved from the cache, or false if the key did not exist within the cache.
     *      If MUST_EXIST was used then an exception will be thrown if the key does not exist within the cache.
     */
    public function get($key, $strictness = IGNORE_MISSING);

    /**
> * Retrieves the value and actual version for the given key, with at least the required version. * Retrieves an array of values for an array of keys. > * * > * If there is no value for the key, or there is a value but it doesn't have the required * Using this function comes with potential performance implications. > * version, then this function will return false (or throw an exception if you set strictness * Not all cache stores will support get_many/set_many operations and in order to replicate this functionality will call > * to MUST_EXIST). * 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 > * This function can be used to make it easier to support localisable caches (where the cache * store does support it, but you should be aware of this fact. > * could be stored on a local server as well as a shared cache). Specifying the version means * > * that it will automatically retrieve the correct version if available, either from the local * @param array $keys The keys of the data being requested. > * server or [if that has an older version] from the shared server. * @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 the cached version is newer than specified version, it will be returned regardless. For * If MUST_EXIST was used and not all keys existed within the cache then an exception will be thrown. > * example, if you request version 4, but the locally cached version is 5, it will be returned. * Otherwise any key that did not exist will have a data value of false within the results. > * If you request version 6, and the locally cached version is 5, then the system will look in */ > * higher-level caches (if any); if there still isn't a version 6 or greater, it will return public function get_many(array $keys, $strictness = IGNORE_MISSING); > * null. > * /** > * You must use this function if you use set_versioned. * Sends a key => value pair to the cache. > * * > * @param string|int $key The key for the data being requested. * <code> > * @param int $requiredversion Minimum required version of the data * // This code will add four entries to the cache, one for each url. > * @param int $strictness One of IGNORE_MISSING or MUST_EXIST. * $cache->set('main', 'http://moodle.org'); > * @param mixed $actualversion If specified, will be set to the actual version number retrieved * $cache->set('docs', 'http://docs.moodle.org'); > * @return mixed Data from the cache, or false if the key did not exist or was too old * $cache->set('tracker', 'http://tracker.moodle.org'); > */ * $cache->set('qa', 'http://qa.moodle.net'); > public function get_versioned($key, int $requiredversion, int $strictness = IGNORE_MISSING, &$actualversion = null); * </code> > * > /**
* @param string|int $key The key for the data being requested. * @param mixed $data The data to set against the key. * @return bool True on success, false otherwise. */ public function set($key, $data); /**
> * Sets the value for the given key with the given version. * Sends several key => value pairs to the cache. > * * > * The cache does not store multiple versions - any existing version will be overwritten with * Using this function comes with potential performance implications. > * this one. This function should only be used if there is a known 'current version' (e.g. * Not all cache stores will support get_many/set_many operations and in order to replicate this functionality will call > * stored in a database table). It only ensures that the cache does not return outdated data. * 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 > * This function can be used to help implement localisable caches (where the cache could be * does support it, but you should be aware of this fact. > * stored on a local server as well as a shared cache). The version will be recorded alongside * > * the item and get_versioned will always return the correct version. * <code> > * * // This code will add four entries to the cache, one for each url. > * The version number must be an integer that always increases. This could be based on the * $cache->set_many(array( > * current time, or a stored value that increases by 1 each time it changes, etc. * 'main' => 'http://moodle.org', > * * 'docs' => 'http://docs.moodle.org', > * If you use this function you must use get_versioned to retrieve the data. * 'tracker' => 'http://tracker.moodle.org', > * * 'qa' => ''http://qa.moodle.net' > * @param string|int $key The key for the data being set. * )); > * @param int $version Integer for the version of the data * </code> > * @param mixed $data The data to set against the key. * > * @return bool True on success, false otherwise. * @param array $keyvaluearray An array of key => value pairs to send to the cache. > */ * @return int The number of items successfully set. It is up to the developer to check this matches the number of items. > public function set_versioned($key, int $version, $data): bool; * ... if they care that is. > */ > /**
public function set_many(array $keyvaluearray); /** * 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 $key * @return bool True if the cache has the requested key, false otherwise. */ public function has($key); /** * 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); /** * 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); /** * 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); /** * 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); } /** * Cache Loader supporting locking. * * This interface should be given to classes already implementing cache_loader that also wish to support locking. * It outlines the required structure for utilising locking functionality when using a cache. * * Can be implemented by any class already implementing the cache_loader interface. */ interface cache_loader_with_locking { /** * Acquires a lock for the given key. * * Please note that this happens automatically if the cache definition requires locking. * it is still made a public method so that adhoc caches can use it if they choose. * However this doesn't guarantee consistent access. It will become the responsibility of the calling code to ensure * locks are acquired, checked, and released. *
> * Prior to Moodle 4,3 this function used to return false if the lock cannot be obtained. It * @param string|int $key > * now always returns true, and throws an exception if the lock cannot be obtained. * @return bool True if the lock could be acquired, false otherwise. > *
< * @return bool True if the lock could be acquired, false otherwise.
> * @return bool Always returns true (for backwards compatibility) > * @throws moodle_exception If the lock cannot be obtained after a timeout
public function acquire_lock($key); /** * Checks if the cache loader owns the lock for the given key. * * Please note that this happens automatically if the cache definition requires locking. * it is still made a public method so that adhoc caches can use it if they choose. * However this doesn't guarantee consistent access. It will become the responsibility of the calling code to ensure * locks are acquired, checked, and released. * * @param string|int $key * @return bool True if this code has the lock, false if there is a lock but this code doesn't have it, * null if there is no lock. */ public function check_lock_state($key); /** * Releases the lock for the given key. * * Please note that this happens automatically if the cache definition requires locking. * it is still made a public method so that adhoc caches can use it if they choose. * However this doesn't guarantee consistent access. It will become the responsibility of the calling code to ensure * locks are acquired, checked, and released. * * @param string|int $key * @return bool True if the lock has been released, false if there was a problem releasing the lock. */ public function release_lock($key); } /** * Cache store feature: locking * * This is a feature that cache stores can implement if they wish to support locking themselves rather * than having the cache loader handle it for them. * * Can be implemented by classes already implementing cache_store. */ interface cache_is_lockable { /** * Acquires a lock on the given key for the given identifier. * * @param string $key The key we are locking. * @param string $ownerid The identifier so we can check if we have the lock or if it is someone else. * The use of this property is entirely optional and implementations can act as they like upon it. * @return bool True if the lock could be acquired, false otherwise. */ public function acquire_lock($key, $ownerid); /** * Test if there is already a lock for the given key and if there is whether it belongs to the calling code. * * @param string $key The key we are locking. * @param string $ownerid The identifier so we can check if we have the lock or if it is someone else. * @return bool True if this code has the lock, false if there is a lock but this code doesn't have it, null if there * is no lock. */ public function check_lock_state($key, $ownerid); /** * Releases the lock on the given key. * * @param string $key The key we are locking. * @param string $ownerid The identifier so we can check if we have the lock or if it is someone else. * The use of this property is entirely optional and implementations can act as they like upon it. * @return bool True if the lock has been released, false if there was a problem releasing the lock. */ public function release_lock($key, $ownerid); } /** * Cache store feature: key awareness. * * This is a feature that cache stores and cache loaders can both choose to implement. * If a cache store implements this then it will be made responsible for tests for items within the cache. * If the cache store being used doesn't implement this then it will be the responsibility of the cache loader to use the * equivalent get methods to mimick the functionality of these tests. * * Cache stores should only override these methods if they natively support such features or if they have a better performing * means of performing these tests than the handling that would otherwise take place in the cache_loader. * * Can be implemented by classes already implementing cache_store. */ interface cache_is_key_aware { /** * 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 $key * @return bool True if the cache has the requested key, false otherwise. */ public function has($key); /** * 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); /** * 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); } /** * Cache store feature: keys are searchable. * * Cache stores can choose to implement this interface. * In order for a store to be usable as a session cache it must implement this interface. * * @since Moodle 2.4.4 */ interface cache_is_searchable { /** * Finds all of the keys being used by the cache store. * * @return array. */ public function find_all(); /** * Finds all of the keys whose keys start with the given prefix. * * @param string $prefix */ public function find_by_prefix($prefix); } /** * Cache store feature: configurable. * * This feature should be implemented by all cache stores that are configurable when adding an instance. * It requires the implementation of methods required to convert form data into the a configuration array for the * store instance, and then the reverse converting configuration data into an array that can be used to set the * data for the edit form. * * Can be implemented by classes already implementing cache_store. */ interface cache_is_configurable { /** * Given the data from the add instance form this function creates a configuration array. * * @param stdClass $data * @return array */ public static function config_get_configuration_array($data); /** * Allows the cache store to set its data against the edit form before it is shown to the user. * * @param moodleform $editform * @param array $config */ public static function config_set_edit_form_data(moodleform $editform, array $config); } /** * Cache Data Source. * * The cache data source interface can be implemented by any class within Moodle. * If implemented then the class can be reference in a cache definition and will be used to load information that cannot be * retrieved from the cache. As part of its retrieval that information will also be loaded into the cache. * * This allows developers to created a complete cache solution that can be used through code ensuring consistent cache * interaction and loading. Allowing them in turn to centralise code and help keeps things more easily maintainable. * * Can be implemented by any class. * * @package core * @category cache * @copyright 2012 Sam Hemelryk * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later */ interface cache_data_source { /** * Returns an instance of the data source class that the cache can use for loading data using the other methods * specified by this interface. * * @param cache_definition $definition * @return object */ public static function get_instance_for_cache(cache_definition $definition); /** * Loads the data for the key provided ready formatted for caching. * * @param string|int $key The key to load. * @return mixed What ever data should be returned, or false if it can't be loaded. */ public function load_for_cache($key); /** * Loads several keys for the cache. * * @param array $keys An array of keys each of which will be string|int. * @return array An array of matching data items. */ public function load_many_for_cache(array $keys); } /**
> * Versionable cache data source. * Cacheable object. > * * > * This interface extends the main cache data source interface to add an extra required method if * This interface can be implemented by any class that is going to be passed into a cache and allows it to take control of the > * the data source is to be used for a versioned cache. * structure and the information about to be cached, as well as how to deal with it when it is retrieved from a cache. > * * Think of it like serialisation and the __sleep and __wakeup methods. > * @package core_cache * This is used because cache stores are responsible for how they interact with data and what they do when storing it. This > */ * interface ensures there is always a guaranteed action. > interface cache_data_source_versionable extends cache_data_source { */ > /** interface cacheable_object { > * Loads the data for the key provided ready formatted for caching. > * /** > * If there is no data for that key, or if the data for the required key has an older version * Prepares the object for caching. Works like the __sleep method. > * than the specified $requiredversion, then this returns null. * > * * @return mixed The data to cache, can be anything except a class that implements the cacheable_object... that would > * If there is data then $actualversion should be set to the actual version number retrieved * be dumb. > * (may be the same as $requiredversion or newer). */ > * public function prepare_to_cache(); > * @param string|int $key The key to load. > * @param int $requiredversion Minimum required version /** > * @param mixed $actualversion Should be set to the actual version number retrieved * Takes the data provided by prepare_to_cache and reinitialises an instance of the associated from it. > * @return mixed What ever data should be returned, or false if it can't be loaded. * > */ * @param mixed $data > public function load_for_cache_versioned($key, int $requiredversion, &$actualversion); * @return object The instance for the given data. > } */ > public static function wake_from_cache($data); > /**
} /** * Cache lock interface * * This interface needs to be inherited by all cache lock plugins. */ interface cache_lock_interface { /** * Constructs an instance of the cache lock given its name and its configuration data * * @param string $name The unique name of the lock instance * @param array $configuration */ public function __construct($name, array $configuration = array()); /** * Acquires a lock on a given key. * * @param string $key The key to acquire a lock for. * @param string $ownerid An unique identifier for the owner of this lock. It is entirely optional for the cache lock plugin * to use this. Each implementation can decide for themselves. * @param bool $block If set to true the application will wait until a lock can be acquired * @return bool True if the lock can be acquired false otherwise. */ public function lock($key, $ownerid, $block = false); /** * Releases the lock held on a certain key. * * @param string $key The key to release the lock for. * @param string $ownerid An unique identifier for the owner of this lock. It is entirely optional for the cache lock plugin * to use this. Each implementation can decide for themselves. * @param bool $forceunlock If set to true the lock will be removed if it exists regardless of whether or not we own it. */ public function unlock($key, $ownerid, $forceunlock = false); /** * Checks the state of the given key. * * Returns true if the key is locked and belongs to the ownerid. * Returns false if the key is locked but does not belong to the ownerid. * Returns null if there is no lock * * @param string $key The key we are checking for. * @param string $ownerid The identifier so we can check if we have the lock or if it is someone else. * @return bool True if this code has the lock, false if there is a lock but this code doesn't have it, null if there * is no lock. */ public function check_state($key, $ownerid); /** * Cleans up any left over locks. * * This function MUST clean up any locks that have been acquired and not released during processing. * Although the situation of acquiring a lock and not releasing it should be insanely rare we need to deal with it. * Things such as unfortunate timeouts etc could cause this situation. */ public function __destruct(); }