cache/classes/store.php

   1 <?php
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   5 // it under the terms of the GNU General Public License as published by
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   8 //
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  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 //
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  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     /**
 149      * Constructs an instance of the cache store.
 150      *
 151      * The constructor should be responsible for creating anything needed by the store that is not
 152      * specific to a definition.
 153      * Tasks such as opening a connection to check it is available are best done here.
 154      * Tasks that are definition specific such as creating a storage area for the definition data
 155      * or creating key tables and indexs are best done within the initialise method.
 156      *
 157      * Once a store has been constructed the cache API will check it is ready to be intialised with
 158      * a definition by called $this->is_ready().
 159      * If the setup of the store failed (connection could not be established for example) then
 160      * that method should return false so that the store instance is not selected for use.
 161      *
 162      * @param string $name The name of the cache store
 163      * @param array $configuration The configuration for this store instance.
 164      */
 165     abstract public function __construct($name, array $configuration = array());
 166
 167     /**
 168      * Returns the name of this store instance.
 169      * @return string
 170      */
 171     abstract public function my_name();
 172
 173     /**
 174      * Initialises a new instance of the cache store given the definition the instance is to be used for.
 175      *
 176      * This function should be used to run any definition specific setup the store instance requires.
 177      * Tasks such as creating storage areas, or creating indexes are best done here.
 178      *
 179      * Its important to note that the initialise method is expected to always succeed.
 180      * If there are setup tasks that may fail they should be done within the __construct method
 181      * and should they fail is_ready should return false.
 182      *
 183      * @param cache_definition $definition
 184      */
 185     abstract public function initialise(cache_definition $definition);
 186
 187     /**
 188      * Returns true if this cache store instance has been initialised.
 189      * @return bool
 190      */
 191     abstract public function is_initialised();
 192
 193     /**
 194      * Returns true if this cache store instance is ready to use.
 195      * @return bool
 196      */
 197     public function is_ready() {
 198         return forward_static_call(array($this, 'are_requirements_met'));
 199     }
 200
 201     /**
 202      * Retrieves an item from the cache store given its key.
 203      *
 204      * @param string $key The key to retrieve
 205      * @return mixed The data that was associated with the key, or false if the key did not exist.
 206      */
 207     abstract public function get($key);
 208
 209     /**
 210      * Retrieves several items from the cache store in a single transaction.
 211      *
 212      * 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.
 213      *
 214      * @param array $keys The array of keys to retrieve
 215      * @return array An array of items from the cache. There will be an item for each key, those that were not in the store will
 216      *      be set to false.
 217      */
 218     abstract public function get_many($keys);
 219
 220     /**
 221      * Sets an item in the cache given its key and data value.
 222      *
 223      * @param string $key The key to use.
 224      * @param mixed $data The data to set.
 225      * @return bool True if the operation was a success false otherwise.
 226      */
 227     abstract public function set($key, $data);
 228
 229     /**
 230      * Sets many items in the cache in a single transaction.
 231      *
 232      * @param array $keyvaluearray An array of key value pairs. Each item in the array will be an associative array with two
 233      *      keys, 'key' and 'value'.
 234      * @return int The number of items successfully set. It is up to the developer to check this matches the number of items
 235      *      sent ... if they care that is.
 236      */
 237     abstract public function set_many(array $keyvaluearray);
 238
 239     /**
 240      * Deletes an item from the cache store.
 241      *
 242      * @param string $key The key to delete.
 243      * @return bool Returns true if the operation was a success, false otherwise.
 244      */
 245     abstract public function delete($key);
 246
 247     /**
 248      * Deletes several keys from the cache in a single action.
 249      *
 250      * @param array $keys The keys to delete
 251      * @return int The number of items successfully deleted.
 252      */
 253     abstract public function delete_many(array $keys);
 254
 255     /**
 256      * Purges the cache deleting all items within it.
 257      *
 258      * @return boolean True on success. False otherwise.
 259      */
 260     abstract public function purge();
 261
 262     /**
 263      * @deprecated since 2.5
 264      * @see \cache_store::instance_deleted()
 265      */
 266     public function cleanup() {
 267         throw new coding_exception('cache_store::cleanup() can not be used anymore.' .
 268             ' Please use cache_store::instance_deleted() instead.');
 269     }
 270
 271     /**
 272      * Performs any necessary operation when the store instance has been created.
 273      *
 274      * @since Moodle 2.5
 275      */
 276     public function instance_created() {
 277         // By default, do nothing.
 278     }
 279
 280     /**
 281      * Performs any necessary operation when the store instance is being deleted.
 282      *
 283      * This method may be called before the store has been initialised.
 284      *
 285      * @since Moodle 2.5
 286      * @see cleanup()
 287      */
 288     public function instance_deleted() {
 289         if (method_exists($this, 'cleanup')) {
 290             // There used to be a legacy function called cleanup, it was renamed to instance delete.
 291             // To be removed in 2.6.
 292             $this->cleanup();
 293         }
 294     }
 295
 296     /**
 297      * Returns true if the user can add an instance of the store plugin.
 298      *
 299      * @return bool
 300      */
 301     public static function can_add_instance() {
 302         return true;
 303     }
 304
 305     /**
 306      * Returns true if the store instance guarantees data.
 307      *
 308      * @return bool
 309      */
 310     public function supports_data_guarantee() {
 311         return $this::get_supported_features() & self::SUPPORTS_DATA_GUARANTEE;
 312     }
 313
 314     /**
 315      * Returns true if the store instance supports multiple identifiers.
 316      *
 317      * @return bool
 318      */
 319     public function supports_multiple_identifiers() {
 320         return $this::get_supported_features() & self::SUPPORTS_MULTIPLE_IDENTIFIERS;
 321     }
 322
 323     /**
 324      * Returns true if the store instance supports native ttl.
 325      *
 326      * @return bool
 327      */
 328     public function supports_native_ttl() {
 329         return $this::get_supported_features() & self::SUPPORTS_NATIVE_TTL;
 330     }
 331
 332     /**
 333      * Returns true if the store instance is searchable.
 334      *
 335      * @return bool
 336      */
 337     public function is_searchable() {
 338         return in_array('cache_is_searchable', class_implements($this));
 339     }
 340
 341     /**
 342      * Returns true if the store automatically dereferences objects.
 343      *
 344      * @return bool
 345      */
 346     public function supports_dereferencing_objects() {
 347         return $this::get_supported_features() & self::DEREFERENCES_OBJECTS;
 348     }
 349
 350     /**
 351      * Creates a clone of this store instance ready to be initialised.
 352      *
 353      * This method is used so that a cache store needs only be constructed once.
 354      * Future requests for an instance of the store will be given a cloned instance.
 355      *
 356      * If you are writing a cache store that isn't compatible with the clone operation
 357      * you can override this method to handle any situations you want before cloning.
 358      *
 359      * @param array $details An array containing the details of the store from the cache config.
 360      * @return cache_store
 361      */
 362     public function create_clone(array $details = array()) {
 363         // By default we just run clone.
 364         // Any stores that have an issue with this will need to override the create_clone method.
 365         return clone($this);
 366     }
 367
 368     /**
 369      * Can be overridden to return any warnings this store instance should make to the admin.
 370      *
 371      * This should be used to notify things like configuration conflicts etc.
 372      * The warnings returned here will be displayed on the cache configuration screen.
 373      *
 374      * @return string[] An array of warning strings from the store instance.
 375      */
 376     public function get_warnings() {
 377         return array();
 378     }
 379
 380     /**
 381      * Returns true if this cache store instance is both suitable for testing, and ready for testing.
 382      *
 383      * Cache stores that support being used as the default store for unit and acceptance testing should
 384      * override this function and return true if there requirements have been met.
 385      *
 386      * @return bool
 387      */
 388     public static function ready_to_be_used_for_testing() {
 389         return false;
 390     }
 391 }