CachedStorage.php in Drupal 9

Namespace

Drupal\Core\Config

File

core/lib/Drupal/Core/Config/CachedStorage.php

<?php

namespace Drupal\Core\Config;

use Drupal\Core\Cache\CacheBackendInterface;
use Drupal\Core\DependencyInjection\DependencySerializationTrait;

/**
 * Defines the cached storage.
 *
 * The class gets another storage and a cache backend injected. It reads from
 * the cache and delegates the read to the storage on a cache miss. It also
 * handles cache invalidation.
 */
class CachedStorage implements StorageInterface, StorageCacheInterface {
  use DependencySerializationTrait;

  /**
   * The configuration storage to be cached.
   *
   * @var \Drupal\Core\Config\StorageInterface
   */
  protected $storage;

  /**
   * The instantiated Cache backend.
   *
   * @var \Drupal\Core\Cache\CacheBackendInterface
   */
  protected $cache;

  /**
   * List of listAll() prefixes with their results.
   *
   * @var array
   */
  protected $findByPrefixCache = [];

  /**
   * Constructs a new CachedStorage.
   *
   * @param \Drupal\Core\Config\StorageInterface $storage
   *   A configuration storage to be cached.
   * @param \Drupal\Core\Cache\CacheBackendInterface $cache
   *   A cache backend used to store configuration.
   */
  public function __construct(StorageInterface $storage, CacheBackendInterface $cache) {
    $this->storage = $storage;
    $this->cache = $cache;
  }

  /**
   * {@inheritdoc}
   */
  public function exists($name) {

    // The cache would read in the entire data (instead of only checking whether
    // any data exists), and on a potential cache miss, an additional storage
    // lookup would have to happen, so check the storage directly.
    return $this->storage
      ->exists($name);
  }

  /**
   * {@inheritdoc}
   */
  public function read($name) {
    $cache_key = $this
      ->getCacheKey($name);
    if ($cache = $this->cache
      ->get($cache_key)) {

      // The cache contains either the cached configuration data or FALSE
      // if the configuration file does not exist.
      return $cache->data;
    }

    // Read from the storage on a cache miss and cache the data. Also cache
    // information about missing configuration objects.
    $data = $this->storage
      ->read($name);
    $this->cache
      ->set($cache_key, $data);
    return $data;
  }

  /**
   * {@inheritdoc}
   */
  public function readMultiple(array $names) {
    $data_to_return = [];
    $cache_keys_map = $this
      ->getCacheKeys($names);
    $cache_keys = array_values($cache_keys_map);
    $cached_list = $this->cache
      ->getMultiple($cache_keys);
    if (!empty($cache_keys)) {

      // $cache_keys_map contains the full $name => $cache_key map, while
      // $cache_keys contains just the $cache_key values that weren't found in
      // the cache.
      // @see \Drupal\Core\Cache\CacheBackendInterface::getMultiple()
      $names_to_get = array_keys(array_intersect($cache_keys_map, $cache_keys));
      $list = $this->storage
        ->readMultiple($names_to_get);

      // Cache configuration objects that were loaded from the storage, cache
      // missing configuration objects as an explicit FALSE.
      $items = [];
      foreach ($names_to_get as $name) {
        $data = isset($list[$name]) ? $list[$name] : FALSE;
        $data_to_return[$name] = $data;
        $items[$cache_keys_map[$name]] = [
          'data' => $data,
        ];
      }
      $this->cache
        ->setMultiple($items);
    }

    // Add the configuration objects from the cache to the list.
    $cache_keys_inverse_map = array_flip($cache_keys_map);
    foreach ($cached_list as $cache_key => $cache) {
      $name = $cache_keys_inverse_map[$cache_key];
      $data_to_return[$name] = $cache->data;
    }

    // Ensure that only existing configuration objects are returned, filter out
    // cached information about missing objects.
    return array_filter($data_to_return);
  }

  /**
   * {@inheritdoc}
   */
  public function write($name, array $data) {
    if ($this->storage
      ->write($name, $data)) {

      // While not all written data is read back, setting the cache instead of
      // just deleting it avoids cache rebuild stampedes.
      $this->cache
        ->set($this
        ->getCacheKey($name), $data);
      $this->findByPrefixCache = [];
      return TRUE;
    }
    return FALSE;
  }

  /**
   * {@inheritdoc}
   */
  public function delete($name) {

    // If the cache was the first to be deleted, another process might start
    // rebuilding the cache before the storage is gone.
    if ($this->storage
      ->delete($name)) {
      $this->cache
        ->delete($this
        ->getCacheKey($name));
      $this->findByPrefixCache = [];
      return TRUE;
    }
    return FALSE;
  }

  /**
   * {@inheritdoc}
   */
  public function rename($name, $new_name) {

    // If the cache was the first to be deleted, another process might start
    // rebuilding the cache before the storage is renamed.
    if ($this->storage
      ->rename($name, $new_name)) {
      $this->cache
        ->delete($this
        ->getCacheKey($name));
      $this->cache
        ->delete($this
        ->getCacheKey($new_name));
      $this->findByPrefixCache = [];
      return TRUE;
    }
    return FALSE;
  }

  /**
   * {@inheritdoc}
   */
  public function encode($data) {
    return $this->storage
      ->encode($data);
  }

  /**
   * {@inheritdoc}
   */
  public function decode($raw) {
    return $this->storage
      ->decode($raw);
  }

  /**
   * {@inheritdoc}
   */
  public function listAll($prefix = '') {

    // Do not cache when a prefix is not provided.
    if ($prefix) {
      return $this
        ->findByPrefix($prefix);
    }
    return $this->storage
      ->listAll();
  }

  /**
   * Finds configuration object names starting with a given prefix.
   *
   * Given the following configuration objects:
   * - node.type.article
   * - node.type.page
   *
   * Passing the prefix 'node.type.' will return an array containing the above
   * names.
   *
   * @param string $prefix
   *   The prefix to search for
   *
   * @return array
   *   An array containing matching configuration object names.
   */
  protected function findByPrefix($prefix) {
    $cache_key = $this
      ->getCacheKey($prefix);
    if (!isset($this->findByPrefixCache[$cache_key])) {
      $this->findByPrefixCache[$cache_key] = $this->storage
        ->listAll($prefix);
    }
    return $this->findByPrefixCache[$cache_key];
  }

  /**
   * {@inheritdoc}
   */
  public function deleteAll($prefix = '') {

    // If the cache was the first to be deleted, another process might start
    // rebuilding the cache before the storage is renamed.
    $names = $this->storage
      ->listAll($prefix);
    if ($this->storage
      ->deleteAll($prefix)) {
      $this->cache
        ->deleteMultiple($this
        ->getCacheKeys($names));
      return TRUE;
    }
    return FALSE;
  }

  /**
   * Clears the static list cache.
   */
  public function resetListCache() {
    $this->findByPrefixCache = [];
  }

  /**
   * {@inheritdoc}
   */
  public function createCollection($collection) {
    return new static($this->storage
      ->createCollection($collection), $this->cache);
  }

  /**
   * {@inheritdoc}
   */
  public function getAllCollectionNames() {
    return $this->storage
      ->getAllCollectionNames();
  }

  /**
   * {@inheritdoc}
   */
  public function getCollectionName() {
    return $this->storage
      ->getCollectionName();
  }

  /**
   * Returns a cache key for a configuration name using the collection.
   *
   * @param string $name
   *   The configuration name.
   *
   * @return string
   *   The cache key for the configuration name.
   */
  protected function getCacheKey($name) {
    return $this
      ->getCollectionPrefix() . $name;
  }

  /**
   * Returns a cache key map for an array of configuration names.
   *
   * @param array $names
   *   The configuration names.
   *
   * @return array
   *   An array of cache keys keyed by configuration names.
   */
  protected function getCacheKeys(array $names) {
    $prefix = $this
      ->getCollectionPrefix();
    $cache_keys = array_map(function ($name) use ($prefix) {
      return $prefix . $name;
    }, $names);
    return array_combine($names, $cache_keys);
  }

  /**
   * Returns a cache ID prefix to use for the collection.
   *
   * @return string
   *   The cache ID prefix.
   */
  protected function getCollectionPrefix() {
    $collection = $this->storage
      ->getCollectionName();
    if ($collection == StorageInterface::DEFAULT_COLLECTION) {
      return '';
    }
    return $collection . ':';
  }

}

Classes

Name	Description
CachedStorage	Defines the cached storage.