[Summary view]

Differences Between: [Versions 39 and 400] [Versions 39 and 401] [Versions 39 and 402] [Versions 39 and 403]

   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       * Generates the appropriate configuration required for unit testing.
  85       *
  86       * @return array Array of unit test configuration data to be used by initialise().
  87       */
  88      public static function unit_test_configuration();
  89  }
  90  
  91  /**
  92   * Abstract cache store class.
  93   *
  94   * All cache store plugins must extend this base class.
  95   * It lays down the foundation for what is required of a cache store plugin.
  96   *
  97   * @since Moodle 2.4
  98   * @package    core
  99   * @category   cache
 100   * @copyright  2012 Sam Hemelryk
 101   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 102   */
 103  abstract class cache_store implements cache_store_interface {
 104  
 105      // Constants for features a cache store can support
 106  
 107      /**
 108       * Supports multi-part keys
 109       */
 110      const SUPPORTS_MULTIPLE_IDENTIFIERS = 1;
 111      /**
 112       * Ensures data remains in the cache once set.
 113       */
 114      const SUPPORTS_DATA_GUARANTEE = 2;
 115      /**
 116       * Supports a native ttl system.
 117       */
 118      const SUPPORTS_NATIVE_TTL = 4;
 119  
 120      /**
 121       * The cache is searchable by key.
 122       */
 123      const IS_SEARCHABLE = 8;
 124  
 125      /**
 126       * The cache store dereferences objects.
 127       *
 128       * When set, loaders will assume that all data coming from this store has already had all references
 129       * resolved.  So even for complex object structures it will not try to remove references again.
 130       */
 131      const DEREFERENCES_OBJECTS = 16;
 132  
 133      // Constants for the modes of a cache store
 134  
 135      /**
 136       * Application caches. These are shared caches.
 137       */
 138      const MODE_APPLICATION = 1;
 139      /**
 140       * Session caches. Just access to the PHP session.
 141       */
 142      const MODE_SESSION = 2;
 143      /**
 144       * Request caches. Static caches really.
 145       */
 146      const MODE_REQUEST = 4;
 147      /**
 148       * Static caches.
 149       */
 150      const STATIC_ACCEL = '** static accel. **';
 151  
 152      /**
 153       * Constructs an instance of the cache store.
 154       *
 155       * The constructor should be responsible for creating anything needed by the store that is not
 156       * specific to a definition.
 157       * Tasks such as opening a connection to check it is available are best done here.
 158       * Tasks that are definition specific such as creating a storage area for the definition data
 159       * or creating key tables and indexs are best done within the initialise method.
 160       *
 161       * Once a store has been constructed the cache API will check it is ready to be intialised with
 162       * a definition by called $this->is_ready().
 163       * If the setup of the store failed (connection could not be established for example) then
 164       * that method should return false so that the store instance is not selected for use.
 165       *
 166       * @param string $name The name of the cache store
 167       * @param array $configuration The configuration for this store instance.
 168       */
 169      abstract public function __construct($name, array $configuration = array());
 170  
 171      /**
 172       * Returns the name of this store instance.
 173       * @return string
 174       */
 175      abstract public function my_name();
 176  
 177      /**
 178       * Initialises a new instance of the cache store given the definition the instance is to be used for.
 179       *
 180       * This function should be used to run any definition specific setup the store instance requires.
 181       * Tasks such as creating storage areas, or creating indexes are best done here.
 182       *
 183       * Its important to note that the initialise method is expected to always succeed.
 184       * If there are setup tasks that may fail they should be done within the __construct method
 185       * and should they fail is_ready should return false.
 186       *
 187       * @param cache_definition $definition
 188       */
 189      abstract public function initialise(cache_definition $definition);
 190  
 191      /**
 192       * Returns true if this cache store instance has been initialised.
 193       * @return bool
 194       */
 195      abstract public function is_initialised();
 196  
 197      /**
 198       * Returns true if this cache store instance is ready to use.
 199       * @return bool
 200       */
 201      public function is_ready() {
 202          return forward_static_call(array($this, 'are_requirements_met'));
 203      }
 204  
 205      /**
 206       * Retrieves an item from the cache store given its key.
 207       *
 208       * @param string $key The key to retrieve
 209       * @return mixed The data that was associated with the key, or false if the key did not exist.
 210       */
 211      abstract public function get($key);
 212  
 213      /**
 214       * Retrieves several items from the cache store in a single transaction.
 215       *
 216       * 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.
 217       *
 218       * @param array $keys The array of keys to retrieve
 219       * @return array An array of items from the cache. There will be an item for each key, those that were not in the store will
 220       *      be set to false.
 221       */
 222      abstract public function get_many($keys);
 223  
 224      /**
 225       * Sets an item in the cache given its key and data value.
 226       *
 227       * @param string $key The key to use.
 228       * @param mixed $data The data to set.
 229       * @return bool True if the operation was a success false otherwise.
 230       */
 231      abstract public function set($key, $data);
 232  
 233      /**
 234       * Sets many items in the cache in a single transaction.
 235       *
 236       * @param array $keyvaluearray An array of key value pairs. Each item in the array will be an associative array with two
 237       *      keys, 'key' and 'value'.
 238       * @return int The number of items successfully set. It is up to the developer to check this matches the number of items
 239       *      sent ... if they care that is.
 240       */
 241      abstract public function set_many(array $keyvaluearray);
 242  
 243      /**
 244       * Deletes an item from the cache store.
 245       *
 246       * @param string $key The key to delete.
 247       * @return bool Returns true if the operation was a success, false otherwise.
 248       */
 249      abstract public function delete($key);
 250  
 251      /**
 252       * Deletes several keys from the cache in a single action.
 253       *
 254       * @param array $keys The keys to delete
 255       * @return int The number of items successfully deleted.
 256       */
 257      abstract public function delete_many(array $keys);
 258  
 259      /**
 260       * Purges the cache deleting all items within it.
 261       *
 262       * @return boolean True on success. False otherwise.
 263       */
 264      abstract public function purge();
 265  
 266      /**
 267       * @deprecated since 2.5
 268       * @see \cache_store::instance_deleted()
 269       */
 270      public function cleanup() {
 271          throw new coding_exception('cache_store::cleanup() can not be used anymore.' .
 272              ' Please use cache_store::instance_deleted() instead.');
 273      }
 274  
 275      /**
 276       * Performs any necessary operation when the store instance has been created.
 277       *
 278       * @since Moodle 2.5
 279       */
 280      public function instance_created() {
 281          // By default, do nothing.
 282      }
 283  
 284      /**
 285       * Performs any necessary operation when the store instance is being deleted.
 286       *
 287       * This method may be called before the store has been initialised.
 288       *
 289       * @since Moodle 2.5
 290       * @see cleanup()
 291       */
 292      public function instance_deleted() {
 293          if (method_exists($this, 'cleanup')) {
 294              // There used to be a legacy function called cleanup, it was renamed to instance delete.
 295              // To be removed in 2.6.
 296              $this->cleanup();
 297          }
 298      }
 299  
 300      /**
 301       * Returns true if the user can add an instance of the store plugin.
 302       *
 303       * @return bool
 304       */
 305      public static function can_add_instance() {
 306          return true;
 307      }
 308  
 309      /**
 310       * Returns true if the store instance guarantees data.
 311       *
 312       * @return bool
 313       */
 314      public function supports_data_guarantee() {
 315          return $this::get_supported_features() & self::SUPPORTS_DATA_GUARANTEE;
 316      }
 317  
 318      /**
 319       * Returns true if the store instance supports multiple identifiers.
 320       *
 321       * @return bool
 322       */
 323      public function supports_multiple_identifiers() {
 324          return $this::get_supported_features() & self::SUPPORTS_MULTIPLE_IDENTIFIERS;
 325      }
 326  
 327      /**
 328       * Returns true if the store instance supports native ttl.
 329       *
 330       * @return bool
 331       */
 332      public function supports_native_ttl() {
 333          return $this::get_supported_features() & self::SUPPORTS_NATIVE_TTL;
 334      }
 335  
 336      /**
 337       * Returns true if the store instance is searchable.
 338       *
 339       * @return bool
 340       */
 341      public function is_searchable() {
 342          return in_array('cache_is_searchable', class_implements($this));
 343      }
 344  
 345      /**
 346       * Returns true if the store automatically dereferences objects.
 347       *
 348       * @return bool
 349       */
 350      public function supports_dereferencing_objects() {
 351          return $this::get_supported_features() & self::DEREFERENCES_OBJECTS;
 352      }
 353  
 354      /**
 355       * Creates a clone of this store instance ready to be initialised.
 356       *
 357       * This method is used so that a cache store needs only be constructed once.
 358       * Future requests for an instance of the store will be given a cloned instance.
 359       *
 360       * If you are writing a cache store that isn't compatible with the clone operation
 361       * you can override this method to handle any situations you want before cloning.
 362       *
 363       * @param array $details An array containing the details of the store from the cache config.
 364       * @return cache_store
 365       */
 366      public function create_clone(array $details = array()) {
 367          // By default we just run clone.
 368          // Any stores that have an issue with this will need to override the create_clone method.
 369          return clone($this);
 370      }
 371  
 372      /**
 373       * Can be overridden to return any warnings this store instance should make to the admin.
 374       *
 375       * This should be used to notify things like configuration conflicts etc.
 376       * The warnings returned here will be displayed on the cache configuration screen.
 377       *
 378       * @return string[] An array of warning strings from the store instance.
 379       */
 380      public function get_warnings() {
 381          return array();
 382      }
 383  
 384      /**
 385       * Returns true if this cache store instance is both suitable for testing, and ready for testing.
 386       *
 387       * Cache stores that support being used as the default store for unit and acceptance testing should
 388       * override this function and return true if there requirements have been met.
 389       *
 390       * @return bool
 391       */
 392      public static function ready_to_be_used_for_testing() {
 393          return false;
 394      }
 395  }