Chris@0: <?php
Chris@0: 
Chris@0: namespace Drupal\page_cache\StackMiddleware;
Chris@0: 
Chris@0: use Drupal\Core\Cache\Cache;
Chris@0: use Drupal\Core\Cache\CacheableResponseInterface;
Chris@0: use Drupal\Core\Cache\CacheBackendInterface;
Chris@0: use Drupal\Core\PageCache\RequestPolicyInterface;
Chris@0: use Drupal\Core\PageCache\ResponsePolicyInterface;
Chris@0: use Drupal\Core\Site\Settings;
Chris@0: use Symfony\Component\HttpFoundation\BinaryFileResponse;
Chris@0: use Symfony\Component\HttpFoundation\Request;
Chris@0: use Symfony\Component\HttpFoundation\Response;
Chris@0: use Symfony\Component\HttpFoundation\StreamedResponse;
Chris@0: use Symfony\Component\HttpKernel\HttpKernelInterface;
Chris@0: 
Chris@0: /**
Chris@0:  * Executes the page caching before the main kernel takes over the request.
Chris@0:  */
Chris@0: class PageCache implements HttpKernelInterface {
Chris@0: 
Chris@0:   /**
Chris@0:    * The wrapped HTTP kernel.
Chris@0:    *
Chris@0:    * @var \Symfony\Component\HttpKernel\HttpKernelInterface
Chris@0:    */
Chris@0:   protected $httpKernel;
Chris@0: 
Chris@0:   /**
Chris@0:    * The cache bin.
Chris@0:    *
Chris@17:    * @var \Drupal\Core\Cache\CacheBackendInterface
Chris@0:    */
Chris@0:   protected $cache;
Chris@0: 
Chris@0:   /**
Chris@0:    * A policy rule determining the cacheability of a request.
Chris@0:    *
Chris@0:    * @var \Drupal\Core\PageCache\RequestPolicyInterface
Chris@0:    */
Chris@0:   protected $requestPolicy;
Chris@0: 
Chris@0:   /**
Chris@0:    * A policy rule determining the cacheability of the response.
Chris@0:    *
Chris@0:    * @var \Drupal\Core\PageCache\ResponsePolicyInterface
Chris@0:    */
Chris@0:   protected $responsePolicy;
Chris@0: 
Chris@0:   /**
Chris@18:    * The cache ID for the (master) request.
Chris@18:    *
Chris@18:    * @var string
Chris@18:    */
Chris@18:   protected $cid;
Chris@18: 
Chris@18:   /**
Chris@0:    * Constructs a PageCache object.
Chris@0:    *
Chris@0:    * @param \Symfony\Component\HttpKernel\HttpKernelInterface $http_kernel
Chris@0:    *   The decorated kernel.
Chris@0:    * @param \Drupal\Core\Cache\CacheBackendInterface $cache
Chris@0:    *   The cache bin.
Chris@0:    * @param \Drupal\Core\PageCache\RequestPolicyInterface $request_policy
Chris@0:    *   A policy rule determining the cacheability of a request.
Chris@0:    * @param \Drupal\Core\PageCache\ResponsePolicyInterface $response_policy
Chris@0:    *   A policy rule determining the cacheability of the response.
Chris@0:    */
Chris@0:   public function __construct(HttpKernelInterface $http_kernel, CacheBackendInterface $cache, RequestPolicyInterface $request_policy, ResponsePolicyInterface $response_policy) {
Chris@0:     $this->httpKernel = $http_kernel;
Chris@0:     $this->cache = $cache;
Chris@0:     $this->requestPolicy = $request_policy;
Chris@0:     $this->responsePolicy = $response_policy;
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * {@inheritdoc}
Chris@0:    */
Chris@0:   public function handle(Request $request, $type = self::MASTER_REQUEST, $catch = TRUE) {
Chris@0:     // Only allow page caching on master request.
Chris@0:     if ($type === static::MASTER_REQUEST && $this->requestPolicy->check($request) === RequestPolicyInterface::ALLOW) {
Chris@0:       $response = $this->lookup($request, $type, $catch);
Chris@0:     }
Chris@0:     else {
Chris@0:       $response = $this->pass($request, $type, $catch);
Chris@0:     }
Chris@0: 
Chris@0:     return $response;
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * Sidesteps the page cache and directly forwards a request to the backend.
Chris@0:    *
Chris@0:    * @param \Symfony\Component\HttpFoundation\Request $request
Chris@0:    *   A request object.
Chris@0:    * @param int $type
Chris@0:    *   The type of the request (one of HttpKernelInterface::MASTER_REQUEST or
Chris@0:    *   HttpKernelInterface::SUB_REQUEST)
Chris@0:    * @param bool $catch
Chris@0:    *   Whether to catch exceptions or not
Chris@0:    *
Chris@0:    * @returns \Symfony\Component\HttpFoundation\Response $response
Chris@0:    *   A response object.
Chris@0:    */
Chris@0:   protected function pass(Request $request, $type = self::MASTER_REQUEST, $catch = TRUE) {
Chris@0:     return $this->httpKernel->handle($request, $type, $catch);
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * Retrieves a response from the cache or fetches it from the backend.
Chris@0:    *
Chris@0:    * @param \Symfony\Component\HttpFoundation\Request $request
Chris@0:    *   A request object.
Chris@0:    * @param int $type
Chris@0:    *   The type of the request (one of HttpKernelInterface::MASTER_REQUEST or
Chris@0:    *   HttpKernelInterface::SUB_REQUEST)
Chris@0:    * @param bool $catch
Chris@0:    *   Whether to catch exceptions or not
Chris@0:    *
Chris@0:    * @returns \Symfony\Component\HttpFoundation\Response $response
Chris@0:    *   A response object.
Chris@0:    */
Chris@0:   protected function lookup(Request $request, $type = self::MASTER_REQUEST, $catch = TRUE) {
Chris@0:     if ($response = $this->get($request)) {
Chris@0:       $response->headers->set('X-Drupal-Cache', 'HIT');
Chris@0:     }
Chris@0:     else {
Chris@0:       $response = $this->fetch($request, $type, $catch);
Chris@0:     }
Chris@0: 
Chris@0:     // Only allow caching in the browser and prevent that the response is stored
Chris@0:     // by an external proxy server when the following conditions apply:
Chris@0:     // 1. There is a session cookie on the request.
Chris@0:     // 2. The Vary: Cookie header is on the response.
Chris@0:     // 3. The Cache-Control header does not contain the no-cache directive.
Chris@0:     if ($request->cookies->has(session_name()) &&
Chris@0:       in_array('Cookie', $response->getVary()) &&
Chris@0:       !$response->headers->hasCacheControlDirective('no-cache')) {
Chris@0: 
Chris@0:       $response->setPrivate();
Chris@0:     }
Chris@0: 
Chris@0:     // Perform HTTP revalidation.
Chris@0:     // @todo Use Response::isNotModified() as
Chris@0:     //   per https://www.drupal.org/node/2259489.
Chris@0:     $last_modified = $response->getLastModified();
Chris@0:     if ($last_modified) {
Chris@0:       // See if the client has provided the required HTTP headers.
Chris@0:       $if_modified_since = $request->server->has('HTTP_IF_MODIFIED_SINCE') ? strtotime($request->server->get('HTTP_IF_MODIFIED_SINCE')) : FALSE;
Chris@0:       $if_none_match = $request->server->has('HTTP_IF_NONE_MATCH') ? stripslashes($request->server->get('HTTP_IF_NONE_MATCH')) : FALSE;
Chris@0: 
Chris@0:       if ($if_modified_since && $if_none_match
Chris@0:         // etag must match.
Chris@0:         && $if_none_match == $response->getEtag()
Chris@0:         // if-modified-since must match.
Chris@0:         && $if_modified_since == $last_modified->getTimestamp()) {
Chris@0:         $response->setStatusCode(304);
Chris@0:         $response->setContent(NULL);
Chris@0: 
Chris@0:         // In the case of a 304 response, certain headers must be sent, and the
Chris@0:         // remaining may not (see RFC 2616, section 10.3.5).
Chris@0:         foreach (array_keys($response->headers->all()) as $name) {
Chris@0:           if (!in_array($name, ['content-location', 'expires', 'cache-control', 'vary'])) {
Chris@0:             $response->headers->remove($name);
Chris@0:           }
Chris@0:         }
Chris@0:       }
Chris@0:     }
Chris@0: 
Chris@0:     return $response;
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * Fetches a response from the backend and stores it in the cache.
Chris@0:    *
Chris@0:    * @see drupal_page_header()
Chris@0:    *
Chris@0:    * @param \Symfony\Component\HttpFoundation\Request $request
Chris@0:    *   A request object.
Chris@0:    * @param int $type
Chris@0:    *   The type of the request (one of HttpKernelInterface::MASTER_REQUEST or
Chris@0:    *   HttpKernelInterface::SUB_REQUEST)
Chris@0:    * @param bool $catch
Chris@0:    *   Whether to catch exceptions or not
Chris@0:    *
Chris@0:    * @returns \Symfony\Component\HttpFoundation\Response $response
Chris@0:    *   A response object.
Chris@0:    */
Chris@0:   protected function fetch(Request $request, $type = self::MASTER_REQUEST, $catch = TRUE) {
Chris@0:     /** @var \Symfony\Component\HttpFoundation\Response $response */
Chris@0:     $response = $this->httpKernel->handle($request, $type, $catch);
Chris@0: 
Chris@0:     // Only set the 'X-Drupal-Cache' header if caching is allowed for this
Chris@0:     // response.
Chris@0:     if ($this->storeResponse($request, $response)) {
Chris@0:       $response->headers->set('X-Drupal-Cache', 'MISS');
Chris@0:     }
Chris@0: 
Chris@0:     return $response;
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * Stores a response in the page cache.
Chris@0:    *
Chris@0:    * @param \Symfony\Component\HttpFoundation\Request $request
Chris@0:    *   A request object.
Chris@0:    * @param \Symfony\Component\HttpFoundation\Response $response
Chris@0:    *   A response object that should be stored in the page cache.
Chris@0:    *
Chris@0:    * @returns bool
Chris@0:    */
Chris@0:   protected function storeResponse(Request $request, Response $response) {
Chris@0:     // Drupal's primary cache invalidation architecture is cache tags: any
Chris@0:     // response that varies by a configuration value or data in a content
Chris@0:     // entity should have cache tags, to allow for instant cache invalidation
Chris@0:     // when that data is updated. However, HTTP does not standardize how to
Chris@0:     // encode cache tags in a response. Different CDNs implement their own
Chris@0:     // approaches, and configurable reverse proxies (e.g., Varnish) allow for
Chris@0:     // custom implementations. To keep Drupal's internal page cache simple, we
Chris@0:     // only cache CacheableResponseInterface responses, since those provide a
Chris@0:     // defined API for retrieving cache tags. For responses that do not
Chris@0:     // implement CacheableResponseInterface, there's no easy way to distinguish
Chris@0:     // responses that truly don't depend on any site data from responses that
Chris@0:     // contain invalidation information customized to a particular proxy or
Chris@0:     // CDN.
Chris@0:     // - Drupal modules are encouraged to use CacheableResponseInterface
Chris@0:     //   responses where possible and to leave the encoding of that information
Chris@0:     //   into response headers to the corresponding proxy/CDN integration
Chris@0:     //   modules.
Chris@0:     // - Custom applications that wish to provide internal page cache support
Chris@0:     //   for responses that do not implement CacheableResponseInterface may do
Chris@0:     //   so by replacing/extending this middleware service or adding another
Chris@0:     //   one.
Chris@0:     if (!$response instanceof CacheableResponseInterface) {
Chris@0:       return FALSE;
Chris@0:     }
Chris@0: 
Chris@0:     // Currently it is not possible to cache binary file or streamed responses:
Chris@0:     // https://github.com/symfony/symfony/issues/9128#issuecomment-25088678.
Chris@0:     // Therefore exclude them, even for subclasses that implement
Chris@0:     // CacheableResponseInterface.
Chris@0:     if ($response instanceof BinaryFileResponse || $response instanceof StreamedResponse) {
Chris@0:       return FALSE;
Chris@0:     }
Chris@0: 
Chris@0:     // Allow policy rules to further restrict which responses to cache.
Chris@0:     if ($this->responsePolicy->check($response, $request) === ResponsePolicyInterface::DENY) {
Chris@0:       return FALSE;
Chris@0:     }
Chris@0: 
Chris@0:     $request_time = $request->server->get('REQUEST_TIME');
Chris@0:     // The response passes all of the above checks, so cache it. Page cache
Chris@0:     // entries default to Cache::PERMANENT since they will be expired via cache
Chris@0:     // tags locally. Because of this, page cache ignores max age.
Chris@0:     // - Get the tags from CacheableResponseInterface per the earlier comments.
Chris@0:     // - Get the time expiration from the Expires header, rather than the
Chris@0:     //   interface, but see https://www.drupal.org/node/2352009 about possibly
Chris@0:     //   changing that.
Chris@0:     $expire = 0;
Chris@0:     // 403 and 404 responses can fill non-LRU cache backends and generally are
Chris@0:     // likely to have a low cache hit rate. So do not cache them permanently.
Chris@0:     if ($response->isClientError()) {
Chris@0:       // Cache for an hour by default. If the 'cache_ttl_4xx' setting is
Chris@0:       // set to 0 then do not cache the response.
Chris@0:       $cache_ttl_4xx = Settings::get('cache_ttl_4xx', 3600);
Chris@0:       if ($cache_ttl_4xx > 0) {
Chris@0:         $expire = $request_time + $cache_ttl_4xx;
Chris@0:       }
Chris@0:     }
Chris@0:     // The getExpires method could return NULL if Expires header is not set, so
Chris@0:     // the returned value needs to be checked before calling getTimestamp.
Chris@0:     elseif ($expires = $response->getExpires()) {
Chris@0:       $date = $expires->getTimestamp();
Chris@0:       $expire = ($date > $request_time) ? $date : Cache::PERMANENT;
Chris@0:     }
Chris@0:     else {
Chris@0:       $expire = Cache::PERMANENT;
Chris@0:     }
Chris@0: 
Chris@0:     if ($expire === Cache::PERMANENT || $expire > $request_time) {
Chris@0:       $tags = $response->getCacheableMetadata()->getCacheTags();
Chris@0:       $this->set($request, $response, $expire, $tags);
Chris@0:     }
Chris@0: 
Chris@0:     return TRUE;
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * Returns a response object from the page cache.
Chris@0:    *
Chris@0:    * @param \Symfony\Component\HttpFoundation\Request $request
Chris@0:    *   A request object.
Chris@0:    * @param bool $allow_invalid
Chris@0:    *   (optional) If TRUE, a cache item may be returned even if it is expired or
Chris@0:    *   has been invalidated. Such items may sometimes be preferred, if the
Chris@0:    *   alternative is recalculating the value stored in the cache, especially
Chris@0:    *   if another concurrent request is already recalculating the same value.
Chris@0:    *   The "valid" property of the returned object indicates whether the item is
Chris@0:    *   valid or not. Defaults to FALSE.
Chris@0:    *
Chris@0:    * @return \Symfony\Component\HttpFoundation\Response|false
Chris@0:    *   The cached response or FALSE on failure.
Chris@0:    */
Chris@0:   protected function get(Request $request, $allow_invalid = FALSE) {
Chris@0:     $cid = $this->getCacheId($request);
Chris@0:     if ($cache = $this->cache->get($cid, $allow_invalid)) {
Chris@0:       return $cache->data;
Chris@0:     }
Chris@0:     return FALSE;
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * Stores a response object in the page cache.
Chris@0:    *
Chris@0:    * @param \Symfony\Component\HttpFoundation\Request $request
Chris@0:    *   A request object.
Chris@0:    * @param \Symfony\Component\HttpFoundation\Response $response
Chris@0:    *   The response to store in the cache.
Chris@0:    * @param int $expire
Chris@0:    *   One of the following values:
Chris@0:    *   - CacheBackendInterface::CACHE_PERMANENT: Indicates that the item should
Chris@0:    *     not be removed unless it is deleted explicitly.
Chris@0:    *   - A Unix timestamp: Indicates that the item will be considered invalid
Chris@0:    *     after this time, i.e. it will not be returned by get() unless
Chris@0:    *     $allow_invalid has been set to TRUE. When the item has expired, it may
Chris@0:    *     be permanently deleted by the garbage collector at any time.
Chris@0:    * @param array $tags
Chris@0:    *   An array of tags to be stored with the cache item. These should normally
Chris@0:    *   identify objects used to build the cache item, which should trigger
Chris@0:    *   cache invalidation when updated. For example if a cached item represents
Chris@0:    *   a node, both the node ID and the author's user ID might be passed in as
Chris@0:    *   tags. For example array('node' => array(123), 'user' => array(92)).
Chris@0:    */
Chris@0:   protected function set(Request $request, Response $response, $expire, array $tags) {
Chris@0:     $cid = $this->getCacheId($request);
Chris@0:     $this->cache->set($cid, $response, $expire, $tags);
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * Gets the page cache ID for this request.
Chris@0:    *
Chris@0:    * @param \Symfony\Component\HttpFoundation\Request $request
Chris@0:    *   A request object.
Chris@0:    *
Chris@0:    * @return string
Chris@0:    *   The cache ID for this request.
Chris@0:    */
Chris@0:   protected function getCacheId(Request $request) {
Chris@18:     // Once a cache ID is determined for the request, reuse it for the duration
Chris@18:     // of the request. This ensures that when the cache is written, it is only
Chris@18:     // keyed on request data that was available when it was read. For example,
Chris@18:     // the request format might be NULL during cache lookup and then set during
Chris@18:     // routing, in which case we want to key on NULL during writing, since that
Chris@18:     // will be the value during lookups for subsequent requests.
Chris@18:     if (!isset($this->cid)) {
Chris@18:       $cid_parts = [
Chris@18:         $request->getSchemeAndHttpHost() . $request->getRequestUri(),
Chris@18:         $request->getRequestFormat(NULL),
Chris@18:       ];
Chris@18:       $this->cid = implode(':', $cid_parts);
Chris@18:     }
Chris@18:     return $this->cid;
Chris@0:   }
Chris@0: 
Chris@0: }