name : ResponseCacheStrategy.php <?php /* * This file is part of the Symfony package. * * (c) Fabien Potencier <fabien@symfony.com> * * For the full copyright and license information, please view the LICENSE * file that was distributed with this source code. */ namespace Symfony\Component\HttpKernel\HttpCache; use Symfony\Component\HttpFoundation\Response; /** * ResponseCacheStrategy knows how to compute the Response cache HTTP header * based on the different response cache headers. * * This implementation changes the main response TTL to the smallest TTL received * or force validation if one of the surrogates has validation cache strategy. * * @author Fabien Potencier <fabien@symfony.com> */ class ResponseCacheStrategy implements ResponseCacheStrategyInterface { /** * Cache-Control headers that are sent to the final response if they appear in ANY of the responses. */ private const OVERRIDE_DIRECTIVES = ['private', 'no-cache', 'no-store', 'no-transform', 'must-revalidate', 'proxy-revalidate']; /** * Cache-Control headers that are sent to the final response if they appear in ALL of the responses. */ private const INHERIT_DIRECTIVES = ['public', 'immutable']; private int $embeddedResponses = 0; private bool $isNotCacheableResponseEmbedded = false; private int $age = 0; private \DateTimeInterface|null|false $lastModified = null; private array $flagDirectives = [ 'no-cache' => null, 'no-store' => null, 'no-transform' => null, 'must-revalidate' => null, 'proxy-revalidate' => null, 'public' => null, 'private' => null, 'immutable' => null, ]; private array $ageDirectives = [ 'max-age' => null, 's-maxage' => null, 'expires' => null, ]; /** * @return void */ public function add(Response $response) { ++$this->embeddedResponses; foreach (self::OVERRIDE_DIRECTIVES as $directive) { if ($response->headers->hasCacheControlDirective($directive)) { $this->flagDirectives[$directive] = true; } } foreach (self::INHERIT_DIRECTIVES as $directive) { if (false !== $this->flagDirectives[$directive]) { $this->flagDirectives[$directive] = $response->headers->hasCacheControlDirective($directive); } } $age = $response->getAge(); $this->age = max($this->age, $age); if ($this->willMakeFinalResponseUncacheable($response)) { $this->isNotCacheableResponseEmbedded = true; return; } $isHeuristicallyCacheable = $response->headers->hasCacheControlDirective('public'); $maxAge = $response->headers->hasCacheControlDirective('max-age') ? (int) $response->headers->getCacheControlDirective('max-age') : null; $this->storeRelativeAgeDirective('max-age', $maxAge, $age, $isHeuristicallyCacheable); $sharedMaxAge = $response->headers->hasCacheControlDirective('s-maxage') ? (int) $response->headers->getCacheControlDirective('s-maxage') : $maxAge; $this->storeRelativeAgeDirective('s-maxage', $sharedMaxAge, $age, $isHeuristicallyCacheable); $expires = $response->getExpires(); $expires = null !== $expires ? (int) $expires->format('U') - (int) $response->getDate()->format('U') : null; $this->storeRelativeAgeDirective('expires', $expires >= 0 ? $expires : null, 0, $isHeuristicallyCacheable); if (false !== $this->lastModified) { $lastModified = $response->getLastModified(); $this->lastModified = $lastModified ? max($this->lastModified, $lastModified) : false; } } /** * @return void */ public function update(Response $response) { // if we have no embedded Response, do nothing if (0 === $this->embeddedResponses) { return; } // Remove Etag since it cannot be merged from embedded responses. $response->setEtag(null); $this->add($response); $response->headers->set('Age', $this->age); if ($this->isNotCacheableResponseEmbedded) { $response->setLastModified(null); if ($this->flagDirectives['no-store']) { $response->headers->set('Cache-Control', 'no-cache, no-store, must-revalidate'); } else { $response->headers->set('Cache-Control', 'no-cache, must-revalidate'); } return; } $response->setLastModified($this->lastModified ?: null); $flags = array_filter($this->flagDirectives); if (isset($flags['must-revalidate'])) { $flags['no-cache'] = true; } $response->headers->set('Cache-Control', implode(', ', array_keys($flags))); $maxAge = null; if (is_numeric($this->ageDirectives['max-age'])) { $maxAge = $this->ageDirectives['max-age'] + $this->age; $response->headers->addCacheControlDirective('max-age', $maxAge); } if (is_numeric($this->ageDirectives['s-maxage'])) { $sMaxage = $this->ageDirectives['s-maxage'] + $this->age; if ($maxAge !== $sMaxage) { $response->headers->addCacheControlDirective('s-maxage', $sMaxage); } } if (is_numeric($this->ageDirectives['expires'])) { $date = clone $response->getDate(); $date = $date->modify('+'.($this->ageDirectives['expires'] + $this->age).' seconds'); $response->setExpires($date); } } /** * RFC2616, Section 13.4. * * @see https://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html#sec13.4 */ private function willMakeFinalResponseUncacheable(Response $response): bool { // RFC2616: A response received with a status code of 200, 203, 300, 301 or 410 // MAY be stored by a cache […] unless a cache-control directive prohibits caching. if ($response->headers->hasCacheControlDirective('no-cache') || $response->headers->hasCacheControlDirective('no-store') ) { return true; } // Etag headers cannot be merged, they render the response uncacheable // by default (except if the response also has max-age etc.). if (null === $response->getEtag() && \in_array($response->getStatusCode(), [200, 203, 300, 301, 410])) { return false; } // RFC2616: A response received with any other status code (e.g. status codes 302 and 307) // MUST NOT be returned in a reply to a subsequent request unless there are // cache-control directives or another header(s) that explicitly allow it. $cacheControl = ['max-age', 's-maxage', 'must-revalidate', 'proxy-revalidate', 'public', 'private']; foreach ($cacheControl as $key) { if ($response->headers->hasCacheControlDirective($key)) { return false; } } if ($response->headers->has('Expires')) { return false; } return true; } /** * Store lowest max-age/s-maxage/expires for the final response. * * The response might have been stored in cache a while ago. To keep things comparable, * we have to subtract the age so that the value is normalized for an age of 0. * * If the value is lower than the currently stored value, we update the value, to keep a rolling * minimal value of each instruction. * * If the value is NULL and the isHeuristicallyCacheable parameter is false, the directive will * not be set on the final response. In this case, not all responses had the directive set and no * value can be found that satisfies the requirements of all responses. The directive will be dropped * from the final response. * * If the isHeuristicallyCacheable parameter is true, however, the current response has been marked * as cacheable in a public (shared) cache, but did not provide an explicit lifetime that would serve * as an upper bound. In this case, we can proceed and possibly keep the directive on the final response. */ private function storeRelativeAgeDirective(string $directive, ?int $value, int $age, bool $isHeuristicallyCacheable): void { if (null === $value) { if ($isHeuristicallyCacheable) { /* * See https://datatracker.ietf.org/doc/html/rfc7234#section-4.2.2 * This particular response does not require maximum lifetime; heuristics might be applied. * Other responses, however, might have more stringent requirements on maximum lifetime. * So, return early here so that the final response can have the more limiting value set. */ return; } $this->ageDirectives[$directive] = false; } if (false !== $this->ageDirectives[$directive]) { $value -= $age; $this->ageDirectives[$directive] = null !== $this->ageDirectives[$directive] ? min($this->ageDirectives[$directive], $value) : $value; } } }