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   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   * This file contains the cache factory class.
  19   *
  20   * This file is part of Moodle's cache API, affectionately called MUC.
  21   * It contains the components that are requried 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   * The cache factory class.
  33   *
  34   * This factory class is important because it stores instances of objects used by the cache API and returns them upon requests.
  35   * This allows us to both reuse objects saving on overhead, and gives us an easy place to "reset" the cache API in situations that
  36   * we need such as unit testing.
  37   *
  38   * @copyright  2012 Sam Hemelryk
  39   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  40   */
  41  class cache_factory {
  42  
  43      /** The cache has not been initialised yet. */
  44      const STATE_UNINITIALISED = 0;
  45      /** The cache is in the process of initialising itself. */
  46      const STATE_INITIALISING = 1;
  47      /** The cache is in the process of saving its configuration file. */
  48      const STATE_SAVING = 2;
  49      /** The cache is ready to use. */
  50      const STATE_READY = 3;
  51      /** The cache is currently updating itself */
  52      const STATE_UPDATING = 4;
  53      /** The cache encountered an error while initialising. */
  54      const STATE_ERROR_INITIALISING = 9;
  55      /** The cache has been disabled. */
  56      const STATE_DISABLED = 10;
  57      /** The cache stores have been disabled */
  58      const STATE_STORES_DISABLED = 11;
  59  
  60      /**
  61       * An instance of the cache_factory class created upon the first request.
  62       * @var cache_factory
  63       */
  64      protected static $instance;
  65  
  66      /**
  67       * An array containing caches created for definitions
  68       * @var array
  69       */
  70      protected $cachesfromdefinitions = array();
  71  
  72      /**
  73       * Array of caches created by parameters, ad-hoc definitions will have been used.
  74       * @var array
  75       */
  76      protected $cachesfromparams = array();
  77  
  78      /**
  79       * An array of stores organised by definitions.
  80       * @var array
  81       */
  82      protected $definitionstores = array();
  83  
  84      /**
  85       * An array of instantiated stores.
  86       * @var array
  87       */
  88      protected $stores = array();
  89  
  90      /**
  91       * An array of configuration instances
  92       * @var array
  93       */
  94      protected $configs = array();
  95  
  96      /**
  97       * An array of initialised definitions
  98       * @var array
  99       */
 100      protected $definitions = array();
 101  
 102      /**
 103       * An array of lock plugins.
 104       * @var array
 105       */
 106      protected $lockplugins = array();
 107  
 108      /**
 109       * The current state of the cache API.
 110       * @var int
 111       */
 112      protected $state = 0;
 113  
 114      /**
 115       * Returns an instance of the cache_factor method.
 116       *
 117       * @param bool $forcereload If set to true a new cache_factory instance will be created and used.
 118       * @return cache_factory
 119       */
 120      public static function instance($forcereload = false) {
 121          global $CFG;
 122          if ($forcereload || self::$instance === null) {
 123              // Initialise a new factory to facilitate our needs.
 124              if (defined('CACHE_DISABLE_ALL') && CACHE_DISABLE_ALL !== false) {
 125                  // The cache has been disabled. Load disabledlib and start using the factory designed to handle this
 126                  // situation. It will use disabled alternatives where available.
 127                  require_once($CFG->dirroot.'/cache/disabledlib.php');
 128                  self::$instance = new cache_factory_disabled();
 129              } else if ((defined('PHPUNIT_TEST') && PHPUNIT_TEST) || defined('BEHAT_SITE_RUNNING')) {
 130                  // We're using the test factory.
 131                  require_once($CFG->dirroot.'/cache/tests/fixtures/lib.php');
 132                  self::$instance = new cache_phpunit_factory();
 133                  if (defined('CACHE_DISABLE_STORES') && CACHE_DISABLE_STORES !== false) {
 134                      // The cache stores have been disabled.
 135                      self::$instance->set_state(self::STATE_STORES_DISABLED);
 136                  }
 137              } else {
 138                  // We're using the regular factory.
 139                  self::$instance = new cache_factory();
 140                  if (defined('CACHE_DISABLE_STORES') && CACHE_DISABLE_STORES !== false) {
 141                      // The cache stores have been disabled.
 142                      self::$instance->set_state(self::STATE_STORES_DISABLED);
 143                  }
 144              }
 145          }
 146          return self::$instance;
 147      }
 148  
 149      /**
 150       * Protected constructor, please use the static instance method.
 151       */
 152      protected function __construct() {
 153          // Nothing to do here.
 154      }
 155  
 156      /**
 157       * Resets the arrays containing instantiated caches, stores, and config instances.
 158       */
 159      public static function reset() {
 160          $factory = self::instance();
 161          $factory->reset_cache_instances();
 162          $factory->configs = array();
 163          $factory->definitions = array();
 164          $factory->lockplugins = array(); // MUST be null in order to force its regeneration.
 165          // Reset the state to uninitialised.
 166          $factory->state = self::STATE_UNINITIALISED;
 167      }
 168  
 169      /**
 170       * Resets the stores, clearing the array of created stores.
 171       *
 172       * Cache objects still held onto by the code that initialised them will remain as is
 173       * however all future requests for a cache/store will lead to a new instance being re-initialised.
 174       */
 175      public function reset_cache_instances() {
 176          $this->cachesfromdefinitions = array();
 177          $this->cachesfromparams = array();
 178          $this->stores = array();
 179      }
 180  
 181      /**
 182       * Creates a cache object given the parameters for a definition.
 183       *
 184       * If a cache has already been created for the given definition then that cache instance will be returned.
 185       *
 186       * @param string $component
 187       * @param string $area
 188       * @param array $identifiers
 189       * @param string $unused Used to be data source aggregate however that was removed and this is now unused.
 190       * @return cache_application|cache_session|cache_request
 191       */
 192      public function create_cache_from_definition($component, $area, array $identifiers = array(), $unused = null) {
 193          $definitionname = $component.'/'.$area;
 194          if (isset($this->cachesfromdefinitions[$definitionname])) {
 195              $cache = $this->cachesfromdefinitions[$definitionname];
 196              $cache->set_identifiers($identifiers);
 197              return $cache;
 198          }
 199          $definition = $this->create_definition($component, $area);
 200          $definition->set_identifiers($identifiers);
 201          $cache = $this->create_cache($definition, $identifiers);
 202          // Loaders are always held onto to speed up subsequent requests.
 203          $this->cachesfromdefinitions[$definitionname] = $cache;
 204          return $cache;
 205      }
 206  
 207      /**
 208       * Creates an ad-hoc cache from the given param.
 209       *
 210       * If a cache has already been created using the same params then that cache instance will be returned.
 211       *
 212       * @param int $mode
 213       * @param string $component
 214       * @param string $area
 215       * @param array $identifiers
 216       * @param array $options An array of options, available options are:
 217       *   - simplekeys : Set to true if the keys you will use are a-zA-Z0-9_
 218       *   - simpledata : Set to true if the type of the data you are going to store is scalar, or an array of scalar vars
 219       *   - staticacceleration : If set to true the cache will hold onto data passing through it.
 220       *   - staticaccelerationsize : The maximum number of items to hold onto for acceleration purposes.
 221       * @return cache_application|cache_session|cache_request
 222       */
 223      public function create_cache_from_params($mode, $component, $area, array $identifiers = array(), array $options = array()) {
 224          $key = "{$mode}_{$component}_{$area}";
 225          if (array_key_exists($key, $this->cachesfromparams)) {
 226              return $this->cachesfromparams[$key];
 227          }
 228          $definition = cache_definition::load_adhoc($mode, $component, $area, $options);
 229          $definition->set_identifiers($identifiers);
 230          $cache = $this->create_cache($definition, $identifiers);
 231          $this->cachesfromparams[$key] = $cache;
 232          return $cache;
 233      }
 234  
 235      /**
 236       * Common public method to create a cache instance given a definition.
 237       *
 238       * This is used by the static make methods.
 239       *
 240       * @param cache_definition $definition
 241       * @return cache_application|cache_session|cache_store
 242       * @throws coding_exception
 243       */
 244      public function create_cache(cache_definition $definition) {
 245          $class = $definition->get_cache_class();
 246          $stores = cache_helper::get_stores_suitable_for_definition($definition);
 247          foreach ($stores as $key => $store) {
 248              if (!$store::are_requirements_met()) {
 249                  unset($stores[$key]);
 250              }
 251          }
 252          if (count($stores) === 0) {
 253              // Hmm still no stores, better provide a dummy store to mimic functionality. The dev will be none the wiser.
 254              $stores[] = $this->create_dummy_store($definition);
 255          }
 256          $loader = null;
 257          if ($definition->has_data_source()) {
 258              $loader = $definition->get_data_source();
 259          }
 260          while (($store = array_pop($stores)) !== null) {
 261              $loader = new $class($definition, $store, $loader);
 262          }
 263          return $loader;
 264      }
 265  
 266      /**
 267       * Creates a store instance given its name and configuration.
 268       *
 269       * If the store has already been instantiated then the original object will be returned. (reused)
 270       *
 271       * @param string $name The name of the store (must be unique remember)
 272       * @param array $details
 273       * @param cache_definition $definition The definition to instantiate it for.
 274       * @return boolean|cache_store
 275       */
 276      public function create_store_from_config($name, array $details, cache_definition $definition) {
 277          if (!array_key_exists($name, $this->stores)) {
 278              // Properties: name, plugin, configuration, class.
 279              $class = $details['class'];
 280              $store = new $class($details['name'], $details['configuration']);
 281              $this->stores[$name] = $store;
 282          }
 283          /* @var cache_store $store */
 284          $store = $this->stores[$name];
 285          // We check are_requirements_met although we expect is_ready is going to check as well.
 286          if (!$store::are_requirements_met() || !$store->is_ready() || !$store->is_supported_mode($definition->get_mode())) {
 287              return false;
 288          }
 289          // We always create a clone of the original store.
 290          // If we were to clone a store that had already been initialised with a definition then
 291          // we'd run into a myriad of issues.
 292          // We use a method of the store to create a clone rather than just creating it ourselves
 293          // so that if any store out there doesn't handle cloning they can override this method in
 294          // order to address the issues.
 295          $store = $this->stores[$name]->create_clone($details);
 296          $store->initialise($definition);
 297          $definitionid = $definition->get_id();
 298          if (!isset($this->definitionstores[$definitionid])) {
 299              $this->definitionstores[$definitionid] = array();
 300          }
 301          $this->definitionstores[$definitionid][] = $store;
 302          return $store;
 303      }
 304  
 305      /**
 306       * Returns an array of cache stores that have been initialised for use in definitions.
 307       * @param cache_definition $definition
 308       * @return array
 309       */
 310      public function get_store_instances_in_use(cache_definition $definition) {
 311          $id = $definition->get_id();
 312          if (!isset($this->definitionstores[$id])) {
 313              return array();
 314          }
 315          return $this->definitionstores[$id];
 316      }
 317  
 318      /**
 319       * Returns the cache instances that have been used within this request.
 320       * @since Moodle 2.6
 321       * @return array
 322       */
 323      public function get_caches_in_use() {
 324          return $this->cachesfromdefinitions;
 325      }
 326  
 327      /**
 328       * Creates a cache config instance with the ability to write if required.
 329       *
 330       * @param bool $writer If set to true an instance that can update the configuration will be returned.
 331       * @return cache_config|cache_config_writer
 332       */
 333      public function create_config_instance($writer = false) {
 334          global $CFG;
 335  
 336          // The class to use.
 337          $class = 'cache_config';
 338          // Are we running tests of some form?
 339          $testing = (defined('PHPUNIT_TEST') && PHPUNIT_TEST) || defined('BEHAT_SITE_RUNNING');
 340  
 341          // Check if this is a PHPUnit test and redirect to the phpunit config classes if it is.
 342          if ($testing) {
 343              require_once($CFG->dirroot.'/cache/locallib.php');
 344              require_once($CFG->dirroot.'/cache/tests/fixtures/lib.php');
 345              // We have just a single class for PHP unit tests. We don't care enough about its
 346              // performance to do otherwise and having a single method allows us to inject things into it
 347              // while testing.
 348              $class = 'cache_config_testing';
 349          }
 350  
 351          // Check if we need to create a config file with defaults.
 352          $needtocreate = !$class::config_file_exists();
 353  
 354          if ($writer || $needtocreate) {
 355              require_once($CFG->dirroot.'/cache/locallib.php');
 356              if (!$testing) {
 357                  $class .= '_writer';
 358              }
 359          }
 360  
 361          $error = false;
 362          if ($needtocreate) {
 363              // Create the default configuration.
 364              // Update the state, we are now initialising the cache.
 365              self::set_state(self::STATE_INITIALISING);
 366              /** @var cache_config_writer $class */
 367              $configuration = $class::create_default_configuration();
 368              if ($configuration !== true) {
 369                  // Failed to create the default configuration. Disable the cache stores and update the state.
 370                  self::set_state(self::STATE_ERROR_INITIALISING);
 371                  $this->configs[$class] = new $class;
 372                  $this->configs[$class]->load($configuration);
 373                  $error = true;
 374              }
 375          }
 376  
 377          if (!array_key_exists($class, $this->configs)) {
 378              // Create a new instance and call it to load it.
 379              $this->configs[$class] = new $class;
 380              $this->configs[$class]->load();
 381          }
 382  
 383          if (!$error) {
 384              // The cache is now ready to use. Update the state.
 385              self::set_state(self::STATE_READY);
 386          }
 387  
 388          // Return the instance.
 389          return $this->configs[$class];
 390      }
 391  
 392      /**
 393       * Creates a definition instance or returns the existing one if it has already been created.
 394       * @param string $component
 395       * @param string $area
 396       * @param string $unused This used to be data source aggregate - however that functionality has been removed and
 397       *        this argument is now unused.
 398       * @return cache_definition
 399       * @throws coding_exception If the definition cannot be found.
 400       */
 401      public function create_definition($component, $area, $unused = null) {
 402          $id = $component.'/'.$area;
 403          if (!isset($this->definitions[$id])) {
 404              // This is the first time this definition has been requested.
 405              if ($this->is_initialising()) {
 406                  // We're initialising the cache right now. Don't try to create another config instance.
 407                  // We'll just use an ad-hoc cache for the time being.
 408                  $definition = cache_definition::load_adhoc(cache_store::MODE_REQUEST, $component, $area);
 409              } else {
 410                  // Load all the known definitions and find the desired one.
 411                  $instance = $this->create_config_instance();
 412                  $definition = $instance->get_definition_by_id($id);
 413                  if (!$definition) {
 414                      // Oh-oh the definition doesn't exist.
 415                      // There are several things that could be going on here.
 416                      // We may be installing/upgrading a site and have hit a definition that hasn't been used before.
 417                      // Of the developer may be trying to use a newly created definition.
 418                      if ($this->is_updating()) {
 419                          // The cache is presently initialising and the requested cache definition has not been found.
 420                          // This means that the cache initialisation has requested something from a cache (I had recursive nightmares about this).
 421                          // To serve this purpose and avoid errors we are going to make use of an ad-hoc cache rather than
 422                          // search for the definition which would possibly cause an infitite loop trying to initialise the cache.
 423                          $definition = cache_definition::load_adhoc(cache_store::MODE_REQUEST, $component, $area);
 424                      } else {
 425                          // Either a typo of the developer has just created the definition and is using it for the first time.
 426                          $this->reset();
 427                          $instance = $this->create_config_instance(true);
 428                          $instance->update_definitions();
 429                          $definition = $instance->get_definition_by_id($id);
 430                          if (!$definition) {
 431                              throw new coding_exception('The requested cache definition does not exist.'. $id, $id);
 432                          } else if (!$this->is_disabled()) {
 433                              debugging('Cache definitions reparsed causing cache reset in order to locate definition.
 434                                  You should bump the version number to ensure definitions are reprocessed.', DEBUG_DEVELOPER);
 435                          }
 436                          $definition = cache_definition::load($id, $definition);
 437                      }
 438                  } else {
 439                      $definition = cache_definition::load($id, $definition);
 440                  }
 441              }
 442              $this->definitions[$id] = $definition;
 443          }
 444          return $this->definitions[$id];
 445      }
 446  
 447      /**
 448       * Creates a dummy store object for use when a loader has no potential stores to use.
 449       *
 450       * @param cache_definition $definition
 451       * @return cachestore_dummy
 452       */
 453      protected function create_dummy_store(cache_definition $definition) {
 454          global $CFG;
 455          require_once($CFG->dirroot.'/cache/classes/dummystore.php');
 456          $store = new cachestore_dummy();
 457          $store->initialise($definition);
 458          return $store;
 459      }
 460  
 461      /**
 462       * Returns a lock instance ready for use.
 463       *
 464       * @param array $config
 465       * @return cache_lock_interface
 466       */
 467      public function create_lock_instance(array $config) {
 468          global $CFG;
 469          if (!array_key_exists('name', $config) || !array_key_exists('type', $config)) {
 470              throw new coding_exception('Invalid cache lock instance provided');
 471          }
 472          $name = $config['name'];
 473          $type = $config['type'];
 474          unset($config['name']);
 475          unset($config['type']);
 476  
 477          if (!isset($this->lockplugins[$type])) {
 478              $pluginname = substr($type, 10);
 479              $file = $CFG->dirroot."/cache/locks/{$pluginname}/lib.php";
 480              if (file_exists($file) && is_readable($file)) {
 481                  require_once($file);
 482              }
 483              if (!class_exists($type)) {
 484                  throw new coding_exception('Invalid lock plugin requested.');
 485              }
 486              $this->lockplugins[$type] = $type;
 487          }
 488          if (!array_key_exists($type, $this->lockplugins)) {
 489              throw new coding_exception('Invalid cache lock type.');
 490          }
 491          $class = $this->lockplugins[$type];
 492          return new $class($name, $config);
 493      }
 494  
 495      /**
 496       * Returns the current state of the cache API.
 497       *
 498       * @return int
 499       */
 500      public function get_state() {
 501          return $this->state;
 502      }
 503  
 504      /**
 505       * Updates the state fo the cache API.
 506       *
 507       * @param int $state
 508       * @return bool
 509       */
 510      public function set_state($state) {
 511          if ($state <= $this->state) {
 512              return false;
 513          }
 514          $this->state = $state;
 515          return true;
 516      }
 517  
 518      /**
 519       * Informs the factory that the cache is currently updating itself.
 520       *
 521       * This forces the state to upgrading and can only be called once the cache is ready to use.
 522       * Calling it ensure we don't try to reinstantite things when requesting cache definitions that don't exist yet.
 523       */
 524      public function updating_started() {
 525          if ($this->state !== self::STATE_READY) {
 526              return false;
 527          }
 528          $this->state = self::STATE_UPDATING;
 529          return true;
 530      }
 531  
 532      /**
 533       * Informs the factory that the upgrading has finished.
 534       *
 535       * This forces the state back to ready.
 536       */
 537      public function updating_finished() {
 538          $this->state = self::STATE_READY;
 539      }
 540  
 541      /**
 542       * Returns true if the cache API has been disabled.
 543       *
 544       * @return bool
 545       */
 546      public function is_disabled() {
 547          return $this->state === self::STATE_DISABLED;
 548      }
 549  
 550      /**
 551       * Returns true if the cache is currently initialising itself.
 552       *
 553       * This includes both initialisation and saving the cache config file as part of that initialisation.
 554       *
 555       * @return bool
 556       */
 557      public function is_initialising() {
 558          return $this->state === self::STATE_INITIALISING || $this->state === self::STATE_SAVING;
 559      }
 560  
 561      /**
 562       * Returns true if the cache is currently updating itself.
 563       *
 564       * @return bool
 565       */
 566      public function is_updating() {
 567          return $this->state === self::STATE_UPDATING;
 568      }
 569  
 570      /**
 571       * Disables as much of the cache API as possible.
 572       *
 573       * All of the magic associated with the disabled cache is wrapped into this function.
 574       * In switching out the factory for the disabled factory it gains full control over the initialisation of objects
 575       * and can use all of the disabled alternatives.
 576       * Simple!
 577       *
 578       * This function has been marked as protected so that it cannot be abused through the public API presently.
 579       * Perhaps in the future we will allow this, however as per the build up to the first release containing
 580       * MUC it was decided that this was just to risky and abusable.
 581       */
 582      protected static function disable() {
 583          global $CFG;
 584          require_once($CFG->dirroot.'/cache/disabledlib.php');
 585          self::$instance = new cache_factory_disabled();
 586      }
 587  
 588      /**
 589       * Returns true if the cache stores have been disabled.
 590       *
 591       * @return bool
 592       */
 593      public function stores_disabled() {
 594          return $this->state === self::STATE_STORES_DISABLED || $this->is_disabled();
 595      }
 596  
 597      /**
 598       * Disables cache stores.
 599       *
 600       * The cache API will continue to function however none of the actual stores will be used.
 601       * Instead the dummy store will be provided for all cache requests.
 602       * This is useful in situations where you cannot be sure any stores are working.
 603       *
 604       * In order to re-enable the cache you must call the cache factories static reset method:
 605       * <code>
 606       * // Disable the cache factory.
 607       * cache_factory::disable_stores();
 608       * // Re-enable the cache factory by resetting it.
 609       * cache_factory::reset();
 610       * </code>
 611       */
 612      public static function disable_stores() {
 613          // First reset to clear any static acceleration array.
 614          $factory = self::instance();
 615          $factory->reset_cache_instances();
 616          $factory->set_state(self::STATE_STORES_DISABLED);
 617      }
 618  }