class HttpCache

HttpCacheTest.php in drupal/core/vendor/symfony/http-kernel/Symfony/Component/HttpKernel/Tests/HttpCache/HttpCacheTest.php

HttpCacheTestCase.php in drupal/core/vendor/symfony/http-kernel/Symfony/Component/HttpKernel/Tests/HttpCache/HttpCacheTestCase.php

class HttpCache implements HttpKernelInterface, TerminableInterface {
  private $kernel;
  private $store;
  private $request;
  private $esi;
  private $esiCacheStrategy;
  private $traces;

  /**
   * Constructor.
   *
   * The available options are:
   *
   *   * debug:                 If true, the traces are added as a HTTP header to ease debugging
   *
   *   * default_ttl            The number of seconds that a cache entry should be considered
   *                            fresh when no explicit freshness information is provided in
   *                            a response. Explicit Cache-Control or Expires headers
   *                            override this value. (default: 0)
   *
   *   * private_headers        Set of request headers that trigger "private" cache-control behavior
   *                            on responses that don't explicitly state whether the response is
   *                            public or private via a Cache-Control directive. (default: Authorization and Cookie)
   *
   *   * allow_reload           Specifies whether the client can force a cache reload by including a
   *                            Cache-Control "no-cache" directive in the request. Set it to ``true``
   *                            for compliance with RFC 2616. (default: false)
   *
   *   * allow_revalidate       Specifies whether the client can force a cache revalidate by including
   *                            a Cache-Control "max-age=0" directive in the request. Set it to ``true``
   *                            for compliance with RFC 2616. (default: false)
   *
   *   * stale_while_revalidate Specifies the default number of seconds (the granularity is the second as the
   *                            Response TTL precision is a second) during which the cache can immediately return
   *                            a stale response while it revalidates it in the background (default: 2).
   *                            This setting is overridden by the stale-while-revalidate HTTP Cache-Control
   *                            extension (see RFC 5861).
   *
   *   * stale_if_error         Specifies the default number of seconds (the granularity is the second) during which
   *                            the cache can serve a stale response when an error is encountered (default: 60).
   *                            This setting is overridden by the stale-if-error HTTP Cache-Control extension
   *                            (see RFC 5861).
   *
   * @param HttpKernelInterface $kernel  An HttpKernelInterface instance
   * @param StoreInterface      $store   A Store instance
   * @param Esi                 $esi     An Esi instance
   * @param array               $options An array of options
   */
  public function __construct(HttpKernelInterface $kernel, StoreInterface $store, Esi $esi = null, array $options = array()) {
    $this->store = $store;
    $this->kernel = $kernel;

    // needed in case there is a fatal error because the backend is too slow to respond
    register_shutdown_function(array(
      $this->store,
      'cleanup',
    ));
    $this->options = array_merge(array(
      'debug' => false,
      'default_ttl' => 0,
      'private_headers' => array(
        'Authorization',
        'Cookie',
      ),
      'allow_reload' => false,
      'allow_revalidate' => false,
      'stale_while_revalidate' => 2,
      'stale_if_error' => 60,
    ), $options);
    $this->esi = $esi;
    $this->traces = array();
  }

  /**
   * Gets the current store.
   *
   * @return StoreInterface $store A StoreInterface instance
   */
  public function getStore() {
    return $this->store;
  }

  /**
   * Returns an array of events that took place during processing of the last request.
   *
   * @return array An array of events
   */
  public function getTraces() {
    return $this->traces;
  }

  /**
   * Returns a log message for the events of the last request processing.
   *
   * @return string A log message
   */
  public function getLog() {
    $log = array();
    foreach ($this->traces as $request => $traces) {
      $log[] = sprintf('%s: %s', $request, implode(', ', $traces));
    }
    return implode('; ', $log);
  }

  /**
   * Gets the Request instance associated with the master request.
   *
   * @return Request A Request instance
   */
  public function getRequest() {
    return $this->request;
  }

  /**
   * Gets the Kernel instance
   *
   * @return HttpKernelInterface An HttpKernelInterface instance
   */
  public function getKernel() {
    return $this->kernel;
  }

  /**
   * Gets the Esi instance
   *
   * @return Esi An Esi instance
   */
  public function getEsi() {
    return $this->esi;
  }

  /**
   * {@inheritdoc}
   *
   * @api
   */
  public function handle(Request $request, $type = HttpKernelInterface::MASTER_REQUEST, $catch = true) {

    // FIXME: catch exceptions and implement a 500 error page here? -> in Varnish, there is a built-in error page mechanism
    if (HttpKernelInterface::MASTER_REQUEST === $type) {
      $this->traces = array();
      $this->request = $request;
      if (null !== $this->esi) {
        $this->esiCacheStrategy = $this->esi
          ->createCacheStrategy();
      }
    }
    $path = $request
      ->getPathInfo();
    if ($qs = $request
      ->getQueryString()) {
      $path .= '?' . $qs;
    }
    $this->traces[$request
      ->getMethod() . ' ' . $path] = array();
    if (!$request
      ->isMethodSafe()) {
      $response = $this
        ->invalidate($request, $catch);
    }
    elseif ($request->headers
      ->has('expect')) {
      $response = $this
        ->pass($request, $catch);
    }
    else {
      $response = $this
        ->lookup($request, $catch);
    }
    $this
      ->restoreResponseBody($request, $response);
    $response
      ->setDate(new \DateTime(null, new \DateTimeZone('UTC')));
    if (HttpKernelInterface::MASTER_REQUEST === $type && $this->options['debug']) {
      $response->headers
        ->set('X-Symfony-Cache', $this
        ->getLog());
    }
    if (null !== $this->esi) {
      if (HttpKernelInterface::MASTER_REQUEST === $type) {
        $this->esiCacheStrategy
          ->update($response);
      }
      else {
        $this->esiCacheStrategy
          ->add($response);
      }
    }
    $response
      ->prepare($request);
    $response
      ->isNotModified($request);
    return $response;
  }

  /**
   * {@inheritdoc}
   *
   * @api
   */
  public function terminate(Request $request, Response $response) {
    if ($this
      ->getKernel() instanceof TerminableInterface) {
      $this
        ->getKernel()
        ->terminate($request, $response);
    }
  }

  /**
   * Forwards the Request to the backend without storing the Response in the cache.
   *
   * @param Request $request A Request instance
   * @param Boolean $catch   Whether to process exceptions
   *
   * @return Response A Response instance
   */
  protected function pass(Request $request, $catch = false) {
    $this
      ->record($request, 'pass');
    return $this
      ->forward($request, $catch);
  }

  /**
   * Invalidates non-safe methods (like POST, PUT, and DELETE).
   *
   * @param Request $request A Request instance
   * @param Boolean $catch   Whether to process exceptions
   *
   * @return Response A Response instance
   *
   * @throws \Exception
   *
   * @see RFC2616 13.10
   */
  protected function invalidate(Request $request, $catch = false) {
    $response = $this
      ->pass($request, $catch);

    // invalidate only when the response is successful
    if ($response
      ->isSuccessful() || $response
      ->isRedirect()) {
      try {
        $this->store
          ->invalidate($request, $catch);

        // As per the RFC, invalidate Location and Content-Location URLs if present
        foreach (array(
          'Location',
          'Content-Location',
        ) as $header) {
          if ($uri = $response->headers
            ->get($header)) {
            $subRequest = $request::create($uri, 'get', array(), array(), array(), $request->server
              ->all());
            $this->store
              ->invalidate($subRequest);
          }
        }
        $this
          ->record($request, 'invalidate');
      } catch (\Exception $e) {
        $this
          ->record($request, 'invalidate-failed');
        if ($this->options['debug']) {
          throw $e;
        }
      }
    }
    return $response;
  }

  /**
   * Lookups a Response from the cache for the given Request.
   *
   * When a matching cache entry is found and is fresh, it uses it as the
   * response without forwarding any request to the backend. When a matching
   * cache entry is found but is stale, it attempts to "validate" the entry with
   * the backend using conditional GET. When no matching cache entry is found,
   * it triggers "miss" processing.
   *
   * @param Request $request A Request instance
   * @param Boolean $catch   whether to process exceptions
   *
   * @return Response A Response instance
   *
   * @throws \Exception
   */
  protected function lookup(Request $request, $catch = false) {

    // if allow_reload and no-cache Cache-Control, allow a cache reload
    if ($this->options['allow_reload'] && $request
      ->isNoCache()) {
      $this
        ->record($request, 'reload');
      return $this
        ->fetch($request);
    }
    try {
      $entry = $this->store
        ->lookup($request);
    } catch (\Exception $e) {
      $this
        ->record($request, 'lookup-failed');
      if ($this->options['debug']) {
        throw $e;
      }
      return $this
        ->pass($request, $catch);
    }
    if (null === $entry) {
      $this
        ->record($request, 'miss');
      return $this
        ->fetch($request, $catch);
    }
    if (!$this
      ->isFreshEnough($request, $entry)) {
      $this
        ->record($request, 'stale');
      return $this
        ->validate($request, $entry, $catch);
    }
    $this
      ->record($request, 'fresh');
    $entry->headers
      ->set('Age', $entry
      ->getAge());
    return $entry;
  }

  /**
   * Validates that a cache entry is fresh.
   *
   * The original request is used as a template for a conditional
   * GET request with the backend.
   *
   * @param Request  $request A Request instance
   * @param Response $entry   A Response instance to validate
   * @param Boolean  $catch   Whether to process exceptions
   *
   * @return Response A Response instance
   */
  protected function validate(Request $request, Response $entry, $catch = false) {
    $subRequest = clone $request;

    // send no head requests because we want content
    $subRequest
      ->setMethod('GET');

    // add our cached last-modified validator
    $subRequest->headers
      ->set('if_modified_since', $entry->headers
      ->get('Last-Modified'));

    // Add our cached etag validator to the environment.
    // We keep the etags from the client to handle the case when the client
    // has a different private valid entry which is not cached here.
    $cachedEtags = $entry
      ->getEtag() ? array(
      $entry
        ->getEtag(),
    ) : array();
    $requestEtags = $request
      ->getEtags();
    if ($etags = array_unique(array_merge($cachedEtags, $requestEtags))) {
      $subRequest->headers
        ->set('if_none_match', implode(', ', $etags));
    }
    $response = $this
      ->forward($subRequest, $catch, $entry);
    if (304 == $response
      ->getStatusCode()) {
      $this
        ->record($request, 'valid');

      // return the response and not the cache entry if the response is valid but not cached
      $etag = $response
        ->getEtag();
      if ($etag && in_array($etag, $requestEtags) && !in_array($etag, $cachedEtags)) {
        return $response;
      }
      $entry = clone $entry;
      $entry->headers
        ->remove('Date');
      foreach (array(
        'Date',
        'Expires',
        'Cache-Control',
        'ETag',
        'Last-Modified',
      ) as $name) {
        if ($response->headers
          ->has($name)) {
          $entry->headers
            ->set($name, $response->headers
            ->get($name));
        }
      }
      $response = $entry;
    }
    else {
      $this
        ->record($request, 'invalid');
    }
    if ($response
      ->isCacheable()) {
      $this
        ->store($request, $response);
    }
    return $response;
  }

  /**
   * Forwards the Request to the backend and determines whether the response should be stored.
   *
   * This methods is triggered when the cache missed or a reload is required.
   *
   * @param Request $request A Request instance
   * @param Boolean $catch   whether to process exceptions
   *
   * @return Response A Response instance
   */
  protected function fetch(Request $request, $catch = false) {
    $subRequest = clone $request;

    // send no head requests because we want content
    $subRequest
      ->setMethod('GET');

    // avoid that the backend sends no content
    $subRequest->headers
      ->remove('if_modified_since');
    $subRequest->headers
      ->remove('if_none_match');
    $response = $this
      ->forward($subRequest, $catch);
    if ($this
      ->isPrivateRequest($request) && !$response->headers
      ->hasCacheControlDirective('public')) {
      $response
        ->setPrivate(true);
    }
    elseif ($this->options['default_ttl'] > 0 && null === $response
      ->getTtl() && !$response->headers
      ->getCacheControlDirective('must-revalidate')) {
      $response
        ->setTtl($this->options['default_ttl']);
    }
    if ($response
      ->isCacheable()) {
      $this
        ->store($request, $response);
    }
    return $response;
  }

  /**
   * Forwards the Request to the backend and returns the Response.
   *
   * @param Request  $request A Request instance
   * @param Boolean  $catch   Whether to catch exceptions or not
   * @param Response $entry   A Response instance (the stale entry if present, null otherwise)
   *
   * @return Response A Response instance
   */
  protected function forward(Request $request, $catch = false, Response $entry = null) {
    if ($this->esi) {
      $this->esi
        ->addSurrogateEsiCapability($request);
    }

    // modify the X-Forwarded-For header if needed
    $forwardedFor = $request->headers
      ->get('X-Forwarded-For');
    if ($forwardedFor) {
      $request->headers
        ->set('X-Forwarded-For', $forwardedFor . ', ' . $request->server
        ->get('REMOTE_ADDR'));
    }
    else {
      $request->headers
        ->set('X-Forwarded-For', $request->server
        ->get('REMOTE_ADDR'));
    }

    // fix the client IP address by setting it to 127.0.0.1 as HttpCache
    // is always called from the same process as the backend.
    $request->server
      ->set('REMOTE_ADDR', '127.0.0.1');

    // always a "master" request (as the real master request can be in cache)
    $response = $this->kernel
      ->handle($request, HttpKernelInterface::MASTER_REQUEST, $catch);

    // FIXME: we probably need to also catch exceptions if raw === true
    // we don't implement the stale-if-error on Requests, which is nonetheless part of the RFC
    if (null !== $entry && in_array($response
      ->getStatusCode(), array(
      500,
      502,
      503,
      504,
    ))) {
      if (null === ($age = $entry->headers
        ->getCacheControlDirective('stale-if-error'))) {
        $age = $this->options['stale_if_error'];
      }
      if (abs($entry
        ->getTtl()) < $age) {
        $this
          ->record($request, 'stale-if-error');
        return $entry;
      }
    }
    $this
      ->processResponseBody($request, $response);
    return $response;
  }

  /**
   * Checks whether the cache entry is "fresh enough" to satisfy the Request.
   *
   * @param Request  $request A Request instance
   * @param Response $entry   A Response instance
   *
   * @return Boolean true if the cache entry if fresh enough, false otherwise
   */
  protected function isFreshEnough(Request $request, Response $entry) {
    if (!$entry
      ->isFresh()) {
      return $this
        ->lock($request, $entry);
    }
    if ($this->options['allow_revalidate'] && null !== ($maxAge = $request->headers
      ->getCacheControlDirective('max-age'))) {
      return $maxAge > 0 && $maxAge >= $entry
        ->getAge();
    }
    return true;
  }

  /**
   * Locks a Request during the call to the backend.
   *
   * @param Request  $request A Request instance
   * @param Response $entry   A Response instance
   *
   * @return Boolean true if the cache entry can be returned even if it is staled, false otherwise
   */
  protected function lock(Request $request, Response $entry) {

    // try to acquire a lock to call the backend
    $lock = $this->store
      ->lock($request, $entry);

    // there is already another process calling the backend
    if (true !== $lock) {

      // check if we can serve the stale entry
      if (null === ($age = $entry->headers
        ->getCacheControlDirective('stale-while-revalidate'))) {
        $age = $this->options['stale_while_revalidate'];
      }
      if (abs($entry
        ->getTtl()) < $age) {
        $this
          ->record($request, 'stale-while-revalidate');

        // server the stale response while there is a revalidation
        return true;
      }

      // wait for the lock to be released
      $wait = 0;
      while ($this->store
        ->isLocked($request) && $wait < 5000000) {
        usleep(50000);
        $wait += 50000;
      }
      if ($wait < 2000000) {

        // replace the current entry with the fresh one
        $new = $this
          ->lookup($request);
        $entry->headers = $new->headers;
        $entry
          ->setContent($new
          ->getContent());
        $entry
          ->setStatusCode($new
          ->getStatusCode());
        $entry
          ->setProtocolVersion($new
          ->getProtocolVersion());
        foreach ($new->headers
          ->getCookies() as $cookie) {
          $entry->headers
            ->setCookie($cookie);
        }
      }
      else {

        // backend is slow as hell, send a 503 response (to avoid the dog pile effect)
        $entry
          ->setStatusCode(503);
        $entry
          ->setContent('503 Service Unavailable');
        $entry->headers
          ->set('Retry-After', 10);
      }
      return true;
    }

    // we have the lock, call the backend
    return false;
  }

  /**
   * Writes the Response to the cache.
   *
   * @param Request  $request  A Request instance
   * @param Response $response A Response instance
   *
   * @throws \Exception
   */
  protected function store(Request $request, Response $response) {
    try {
      $this->store
        ->write($request, $response);
      $this
        ->record($request, 'store');
      $response->headers
        ->set('Age', $response
        ->getAge());
    } catch (\Exception $e) {
      $this
        ->record($request, 'store-failed');
      if ($this->options['debug']) {
        throw $e;
      }
    }

    // now that the response is cached, release the lock
    $this->store
      ->unlock($request);
  }

  /**
   * Restores the Response body.
   *
   * @param Request  $request  A Request instance
   * @param Response $response A Response instance
   *
   * @return Response A Response instance
   */
  private function restoreResponseBody(Request $request, Response $response) {
    if ($request
      ->isMethod('HEAD') || 304 === $response
      ->getStatusCode()) {
      $response
        ->setContent(null);
      $response->headers
        ->remove('X-Body-Eval');
      $response->headers
        ->remove('X-Body-File');
      return;
    }
    if ($response->headers
      ->has('X-Body-Eval')) {
      ob_start();
      if ($response->headers
        ->has('X-Body-File')) {
        include $response->headers
          ->get('X-Body-File');
      }
      else {
        eval('; ?>' . $response
          ->getContent() . '<?php ;');
      }
      $response
        ->setContent(ob_get_clean());
      $response->headers
        ->remove('X-Body-Eval');
      if (!$response->headers
        ->has('Transfer-Encoding')) {
        $response->headers
          ->set('Content-Length', strlen($response
          ->getContent()));
      }
    }
    elseif ($response->headers
      ->has('X-Body-File')) {
      $response
        ->setContent(file_get_contents($response->headers
        ->get('X-Body-File')));
    }
    else {
      return;
    }
    $response->headers
      ->remove('X-Body-File');
  }
  protected function processResponseBody(Request $request, Response $response) {
    if (null !== $this->esi && $this->esi
      ->needsEsiParsing($response)) {
      $this->esi
        ->process($request, $response);
    }
  }

  /**
   * Checks if the Request includes authorization or other sensitive information
   * that should cause the Response to be considered private by default.
   *
   * @param Request $request A Request instance
   *
   * @return Boolean true if the Request is private, false otherwise
   */
  private function isPrivateRequest(Request $request) {
    foreach ($this->options['private_headers'] as $key) {
      $key = strtolower(str_replace('HTTP_', '', $key));
      if ('cookie' === $key) {
        if (count($request->cookies
          ->all())) {
          return true;
        }
      }
      elseif ($request->headers
        ->has($key)) {
        return true;
      }
    }
    return false;
  }

  /**
   * Records that an event took place.
   *
   * @param Request $request A Request instance
   * @param string  $event   The event name
   */
  private function record(Request $request, $event) {
    $path = $request
      ->getPathInfo();
    if ($qs = $request
      ->getQueryString()) {
      $path .= '?' . $qs;
    }
    $this->traces[$request
      ->getMethod() . ' ' . $path][] = $event;
  }

}