Chris@0: <?php
Chris@0: 
Chris@0: namespace Drupal\Core\Cache;
Chris@0: 
Chris@0: /**
Chris@0:  * Defines a chained cache implementation for combining multiple cache backends.
Chris@0:  *
Chris@0:  * Can be used to combine two or more backends together to behave as if they
Chris@0:  * were a single backend.
Chris@0:  *
Chris@0:  * For example a slower, persistent storage engine could be combined with a
Chris@0:  * faster, volatile storage engine. When retrieving items from cache, they will
Chris@0:  * be fetched from the volatile backend first, only falling back to the
Chris@0:  * persistent backend if an item is not available. An item not present in the
Chris@0:  * volatile backend but found in the persistent one will be propagated back up
Chris@0:  * to ensure fast retrieval on the next request. On cache sets and deletes, both
Chris@0:  * backends will be invoked to ensure consistency.
Chris@0:  *
Chris@0:  * @see \Drupal\Core\Cache\ChainedFastBackend
Chris@0:  *
Chris@0:  * @ingroup cache
Chris@0:  */
Chris@0: class BackendChain implements CacheBackendInterface, CacheTagsInvalidatorInterface {
Chris@0: 
Chris@0:   /**
Chris@0:    * Ordered list of CacheBackendInterface instances.
Chris@0:    *
Chris@0:    * @var array
Chris@0:    */
Chris@0:   protected $backends = [];
Chris@0: 
Chris@0:   /**
Chris@0:    * Constructs a DatabaseBackend object.
Chris@0:    *
Chris@0:    * @param string $bin
Chris@0:    *   The cache bin for which the object is created.
Chris@0:    */
Chris@0:   public function __construct($bin) {
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * Appends a cache backend to the cache chain.
Chris@0:    *
Chris@0:    * @param CacheBackendInterface $backend
Chris@0:    *   The cache backend to be appended to the cache chain.
Chris@0:    *
Chris@0:    * @return \Drupal\Core\Cache\BackendChain
Chris@0:    *   The called object.
Chris@0:    */
Chris@0:   public function appendBackend(CacheBackendInterface $backend) {
Chris@0:     $this->backends[] = $backend;
Chris@0: 
Chris@0:     return $this;
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * Prepends a cache backend to the cache chain.
Chris@0:    *
Chris@0:    * @param CacheBackendInterface $backend
Chris@0:    *   The backend to be prepended to the cache chain.
Chris@0:    *
Chris@0:    * @return \Drupal\Core\Cache\BackendChain
Chris@0:    *   The called object.
Chris@0:    */
Chris@0:   public function prependBackend(CacheBackendInterface $backend) {
Chris@0:     array_unshift($this->backends, $backend);
Chris@0: 
Chris@0:     return $this;
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * {@inheritdoc}
Chris@0:    */
Chris@0:   public function get($cid, $allow_invalid = FALSE) {
Chris@0:     foreach ($this->backends as $index => $backend) {
Chris@0:       if (($return = $backend->get($cid, $allow_invalid)) !== FALSE) {
Chris@0:         // We found a result, propagate it to all missed backends.
Chris@0:         if ($index > 0) {
Chris@0:           for ($i = ($index - 1); 0 <= $i; --$i) {
Chris@0:             $this->backends[$i]->set($cid, $return->data, $return->expire, $return->tags);
Chris@0:           }
Chris@0:         }
Chris@0: 
Chris@0:         return $return;
Chris@0:       }
Chris@0:     }
Chris@0: 
Chris@0:     return FALSE;
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * {@inheritdoc}
Chris@0:    */
Chris@0:   public function getMultiple(&$cids, $allow_invalid = FALSE) {
Chris@0:     $return = [];
Chris@0: 
Chris@0:     foreach ($this->backends as $index => $backend) {
Chris@0:       $items = $backend->getMultiple($cids, $allow_invalid);
Chris@0: 
Chris@0:       // Propagate the values that could be retrieved from the current cache
Chris@0:       // backend to all missed backends.
Chris@0:       if ($index > 0 && !empty($items)) {
Chris@0:         for ($i = ($index - 1); 0 <= $i; --$i) {
Chris@0:           foreach ($items as $cached) {
Chris@0:             $this->backends[$i]->set($cached->cid, $cached->data, $cached->expire, $cached->tags);
Chris@0:           }
Chris@0:         }
Chris@0:       }
Chris@0: 
Chris@0:       // Append the values to the previously retrieved ones.
Chris@0:       $return += $items;
Chris@0: 
Chris@0:       if (empty($cids)) {
Chris@0:         // No need to go further if we don't have any cid to fetch left.
Chris@0:         break;
Chris@0:       }
Chris@0:     }
Chris@0: 
Chris@0:     return $return;
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * {@inheritdoc}
Chris@0:    */
Chris@0:   public function set($cid, $data, $expire = Cache::PERMANENT, array $tags = []) {
Chris@0:     foreach ($this->backends as $backend) {
Chris@0:       $backend->set($cid, $data, $expire, $tags);
Chris@0:     }
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * {@inheritdoc}
Chris@0:    */
Chris@0:   public function setMultiple(array $items) {
Chris@0:     foreach ($this->backends as $backend) {
Chris@0:       $backend->setMultiple($items);
Chris@0:     }
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * {@inheritdoc}
Chris@0:    */
Chris@0:   public function delete($cid) {
Chris@0:     foreach ($this->backends as $backend) {
Chris@0:       $backend->delete($cid);
Chris@0:     }
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * {@inheritdoc}
Chris@0:    */
Chris@0:   public function deleteMultiple(array $cids) {
Chris@0:     foreach ($this->backends as $backend) {
Chris@0:       $backend->deleteMultiple($cids);
Chris@0:     }
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * {@inheritdoc}
Chris@0:    */
Chris@0:   public function deleteAll() {
Chris@0:     foreach ($this->backends as $backend) {
Chris@0:       $backend->deleteAll();
Chris@0:     }
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * {@inheritdoc}
Chris@0:    */
Chris@0:   public function invalidate($cid) {
Chris@0:     foreach ($this->backends as $backend) {
Chris@0:       $backend->invalidate($cid);
Chris@0:     }
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * {@inheritdoc}
Chris@0:    */
Chris@0:   public function invalidateMultiple(array $cids) {
Chris@0:     foreach ($this->backends as $backend) {
Chris@0:       $backend->invalidateMultiple($cids);
Chris@0:     }
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * {@inheritdoc}
Chris@0:    */
Chris@0:   public function invalidateTags(array $tags) {
Chris@0:     foreach ($this->backends as $backend) {
Chris@0:       if ($backend instanceof CacheTagsInvalidatorInterface) {
Chris@0:         $backend->invalidateTags($tags);
Chris@0:       }
Chris@0:     }
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * {@inheritdoc}
Chris@0:    */
Chris@0:   public function invalidateAll() {
Chris@0:     foreach ($this->backends as $backend) {
Chris@0:       $backend->invalidateAll();
Chris@0:     }
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * {@inheritdoc}
Chris@0:    */
Chris@0:   public function garbageCollection() {
Chris@0:     foreach ($this->backends as $backend) {
Chris@0:       $backend->garbageCollection();
Chris@0:     }
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * {@inheritdoc}
Chris@0:    */
Chris@0:   public function removeBin() {
Chris@0:     foreach ($this->backends as $backend) {
Chris@0:       $backend->removeBin();
Chris@0:     }
Chris@0:   }
Chris@0: 
Chris@0: }