cache/classes/store.php

   1 <?php
   2 // This file is part of Moodle - http://moodle.org/
   3 //
   4 // Moodle is free software: you can redistribute it and/or modify
   5 // it under the terms of the GNU General Public License as published by
   6 // the Free Software Foundation, either version 3 of the License, or
   7 // (at your option) any later version.
   8 //
   9 // Moodle is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13 //
  14 // You should have received a copy of the GNU General Public License
  15 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
  16
  17 /**
  18  * Cache store - base class
  19  *
  20  * This file is part of Moodle's cache API, affectionately called MUC.
  21  * It contains the components that are required in order to use caching.
  22  *
  23  * @package    core
  24  * @category   cache
  25  * @copyright  2012 Sam Hemelryk
  26  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  27  */
  28
  29 defined('MOODLE_INTERNAL') || die();
  30
  31 /**
  32  * Cache store interface.
  33  *
  34  * This interface defines the static methods that must be implemented by every cache store plugin.
  35  * To ensure plugins implement this class the abstract cache_store class implements this interface.
  36  *
  37  * @package    core
  38  * @category   cache
  39  * @copyright  2012 Sam Hemelryk
  40  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  41  */
  42 interface cache_store_interface {
  43     /**
  44      * Static method to check if the store requirements are met.
  45      *
  46      * @return bool True if the stores software/hardware requirements have been met and it can be used. False otherwise.
  47      */
  48     public static function are_requirements_met();
  49
  50     /**
  51      * Static method to check if a store is usable with the given mode.
  52      *
  53      * @param int $mode One of cache_store::MODE_*
  54      */
  55     public static function is_supported_mode($mode);
  56
  57     /**
  58      * Returns the supported features as a binary flag.
  59      *
  60      * @param array $configuration The configuration of a store to consider specifically.
  61      * @return int The supported features.
  62      */
  63     public static function get_supported_features(array $configuration = array());
  64
  65     /**
  66      * Returns the supported modes as a binary flag.
  67      *
  68      * @param array $configuration The configuration of a store to consider specifically.
  69      * @return int The supported modes.
  70      */
  71     public static function get_supported_modes(array $configuration = array());
  72
  73     /**
  74      * Generates an instance of the cache store that can be used for testing.
  75      *
  76      * Returns an instance of the cache store, or false if one cannot be created.
  77      *
  78      * @param cache_definition $definition
  79      * @return cache_store|false
  80      */
  81     public static function initialise_test_instance(cache_definition $definition);
  82
  83     /**
  84      * Initialises a test instance for unit tests.
  85      *
  86      * This differs from initialise_test_instance in that it doesn't rely on interacting with the config table.
  87      *
  88      * @since 2.8
  89      * @param cache_definition $definition
  90      * @return cache_store|false
  91      */
  92     public static function initialise_unit_test_instance(cache_definition $definition);
  93 }
  94
  95 /**
  96  * Abstract cache store class.
  97  *
  98  * All cache store plugins must extend this base class.
  99  * It lays down the foundation for what is required of a cache store plugin.
 100  *
 101  * @since Moodle 2.4
 102  * @package    core
 103  * @category   cache
 104  * @copyright  2012 Sam Hemelryk
 105  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 106  */
 107 abstract class cache_store implements cache_store_interface {
 108
 109     // Constants for features a cache store can support
 110
 111     /**
 112      * Supports multi-part keys
 113      */
 114     const SUPPORTS_MULTIPLE_IDENTIFIERS = 1;
 115     /**
 116      * Ensures data remains in the cache once set.
 117      */
 118     const SUPPORTS_DATA_GUARANTEE = 2;
 119     /**
 120      * Supports a native ttl system.
 121      */
 122     const SUPPORTS_NATIVE_TTL = 4;
 123
 124     /**
 125      * The cache is searchable by key.
 126      */
 127     const IS_SEARCHABLE = 8;
 128
 129     // Constants for the modes of a cache store
 130
 131     /**
 132      * Application caches. These are shared caches.
 133      */
 134     const MODE_APPLICATION = 1;
 135     /**
 136      * Session caches. Just access to the PHP session.
 137      */
 138     const MODE_SESSION = 2;
 139     /**
 140      * Request caches. Static caches really.
 141      */
 142     const MODE_REQUEST = 4;
 143
 144     /**
 145      * Constructs an instance of the cache store.
 146      *
 147      * The constructor should be responsible for creating anything needed by the store that is not
 148      * specific to a definition.
 149      * Tasks such as opening a connection to check it is available are best done here.
 150      * Tasks that are definition specific such as creating a storage area for the definition data
 151      * or creating key tables and indexs are best done within the initialise method.
 152      *
 153      * Once a store has been constructed the cache API will check it is ready to be intialised with
 154      * a definition by called $this->is_ready().
 155      * If the setup of the store failed (connection could not be established for example) then
 156      * that method should return false so that the store instance is not selected for use.
 157      *
 158      * @param string $name The name of the cache store
 159      * @param array $configuration The configuration for this store instance.
 160      */
 161     abstract public function __construct($name, array $configuration = array());
 162
 163     /**
 164      * Returns the name of this store instance.
 165      * @return string
 166      */
 167     abstract public function my_name();
 168
 169     /**
 170      * Initialises a new instance of the cache store given the definition the instance is to be used for.
 171      *
 172      * This function should be used to run any definition specific setup the store instance requires.
 173      * Tasks such as creating storage areas, or creating indexes are best done here.
 174      *
 175      * Its important to note that the initialise method is expected to always succeed.
 176      * If there are setup tasks that may fail they should be done within the __construct method
 177      * and should they fail is_ready should return false.
 178      *
 179      * @param cache_definition $definition
 180      */
 181     abstract public function initialise(cache_definition $definition);
 182
 183     /**
 184      * Returns true if this cache store instance has been initialised.
 185      * @return bool
 186      */
 187     abstract public function is_initialised();
 188
 189     /**
 190      * Returns true if this cache store instance is ready to use.
 191      * @return bool
 192      */
 193     public function is_ready() {
 194         return forward_static_call(array($this, 'are_requirements_met'));
 195     }
 196
 197     /**
 198      * Retrieves an item from the cache store given its key.
 199      *
 200      * @param string $key The key to retrieve
 201      * @return mixed The data that was associated with the key, or false if the key did not exist.
 202      */
 203     abstract public function get($key);
 204
 205     /**
 206      * Retrieves several items from the cache store in a single transaction.
 207      *
 208      * If not all of the items are available in the cache then the data value for those that are missing will be set to false.
 209      *
 210      * @param array $keys The array of keys to retrieve
 211      * @return array An array of items from the cache. There will be an item for each key, those that were not in the store will
 212      *      be set to false.
 213      */
 214     abstract public function get_many($keys);
 215
 216     /**
 217      * Sets an item in the cache given its key and data value.
 218      *
 219      * @param string $key The key to use.
 220      * @param mixed $data The data to set.
 221      * @return bool True if the operation was a success false otherwise.
 222      */
 223     abstract public function set($key, $data);
 224
 225     /**
 226      * Sets many items in the cache in a single transaction.
 227      *
 228      * @param array $keyvaluearray An array of key value pairs. Each item in the array will be an associative array with two
 229      *      keys, 'key' and 'value'.
 230      * @return int The number of items successfully set. It is up to the developer to check this matches the number of items
 231      *      sent ... if they care that is.
 232      */
 233     abstract public function set_many(array $keyvaluearray);
 234
 235     /**
 236      * Deletes an item from the cache store.
 237      *
 238      * @param string $key The key to delete.
 239      * @return bool Returns true if the operation was a success, false otherwise.
 240      */
 241     abstract public function delete($key);
 242
 243     /**
 244      * Deletes several keys from the cache in a single action.
 245      *
 246      * @param array $keys The keys to delete
 247      * @return int The number of items successfully deleted.
 248      */
 249     abstract public function delete_many(array $keys);
 250
 251     /**
 252      * Purges the cache deleting all items within it.
 253      *
 254      * @return boolean True on success. False otherwise.
 255      */
 256     abstract public function purge();
 257
 258     /**
 259      * Performs any necessary clean up when the store instance is being deleted.
 260      *
 261      * @deprecated since 2.5
 262      */
 263     public function cleanup() {
 264         debugging('This function has been renamed to instance_deleted. Please update your calls.', DEBUG_DEVELOPER);
 265     }
 266
 267     /**
 268      * Performs any necessary operation when the store instance has been created.
 269      *
 270      * @since Moodle 2.5
 271      */
 272     public function instance_created() {
 273         // By default, do nothing.
 274     }
 275
 276     /**
 277      * Performs any necessary operation when the store instance is being deleted.
 278      *
 279      * This method may be called before the store has been initialised.
 280      *
 281      * @since Moodle 2.5
 282      * @see cleanup()
 283      */
 284     public function instance_deleted() {
 285         if (method_exists($this, 'cleanup')) {
 286             // There used to be a legacy function called cleanup, it was renamed to instance delete.
 287             // To be removed in 2.6.
 288             $this->cleanup();
 289         }
 290     }
 291
 292     /**
 293      * Returns true if the user can add an instance of the store plugin.
 294      *
 295      * @return bool
 296      */
 297     public static function can_add_instance() {
 298         return true;
 299     }
 300
 301     /**
 302      * Returns true if the store instance guarantees data.
 303      *
 304      * @return bool
 305      */
 306     public function supports_data_guarantee() {
 307         return $this::get_supported_features() & self::SUPPORTS_DATA_GUARANTEE;
 308     }
 309
 310     /**
 311      * Returns true if the store instance supports multiple identifiers.
 312      *
 313      * @return bool
 314      */
 315     public function supports_multiple_identifiers() {
 316         return $this::get_supported_features() & self::SUPPORTS_MULTIPLE_IDENTIFIERS;
 317     }
 318
 319     /**
 320      * Returns true if the store instance supports native ttl.
 321      *
 322      * @return bool
 323      */
 324     public function supports_native_ttl() {
 325         return $this::get_supported_features() & self::SUPPORTS_NATIVE_TTL;
 326     }
 327
 328     /**
 329      * Returns true if the store instance is searchable.
 330      *
 331      * @return bool
 332      */
 333     public function is_searchable() {
 334         return in_array('cache_is_searchable', class_implements($this));
 335     }
 336
 337     /**
 338      * Creates a clone of this store instance ready to be initialised.
 339      *
 340      * This method is used so that a cache store needs only be constructed once.
 341      * Future requests for an instance of the store will be given a cloned instance.
 342      *
 343      * If you are writing a cache store that isn't compatible with the clone operation
 344      * you can override this method to handle any situations you want before cloning.
 345      *
 346      * @param array $details An array containing the details of the store from the cache config.
 347      * @return cache_store
 348      */
 349     public function create_clone(array $details = array()) {
 350         // By default we just run clone.
 351         // Any stores that have an issue with this will need to override the create_clone method.
 352         return clone($this);
 353     }
 354
 355     /**
 356      * Initialises a test instance for unit tests.
 357      *
 358      * This differs from initialise_test_instance in that it doesn't rely on interacting with the config table.
 359      * By default however it calls initialise_test_instance to support backwards compatibility.
 360      *
 361      * @since 2.8
 362      * @param cache_definition $definition
 363      * @return cache_store|false
 364      */
 365     public static function initialise_unit_test_instance(cache_definition $definition) {
 366         return static::initialise_test_instance($definition);
 367     }
 368
 369     /**
 370      * Can be overridden to return any warnings this store instance should make to the admin.
 371      *
 372      * This should be used to notify things like configuration conflicts etc.
 373      * The warnings returned here will be displayed on the cache configuration screen.
 374      *
 375      * @return string[] An array of warning strings from the store instance.
 376      */
 377     public function get_warnings() {
 378         return array();
 379     }
 380
 381     /**
 382      * Returns true if this cache store instance is both suitable for testing, and ready for testing.
 383      *
 384      * Cache stores that support being used as the default store for unit and acceptance testing should
 385      * override this function and return true if there requirements have been met.
 386      *
 387      * @return bool
 388      */
 389     public static function ready_to_be_used_for_testing() {
 390         return false;
 391     }
 392 }