✓Stateless ✓Well-defined TTL ✓Cache / no-cache per resource ✓Cache variations ✓Conditional requests ✓Placeholders for non-cacheable content In an ideal world
namespace App\EventListener; use Symfony\Bridge\Monolog\Logger; use Symfony\Component\HttpFoundation\Response; use Symfony\Component\HttpFoundation\Request; use Symfony\Component\HttpKernel\Event\GetResponseEvent; use Symfony\Component\HttpKernel\Event\FilterResponseEvent; use SymfonyBundles\RedisBundle\Redis\Client as RedisClient; class ConditionalRequestListener { protected $redis; protected $logger; public function __construct(RedisClient $redis) { $this->redis = $redis; } protected function isModified(Request $request, $etag) { if ($etags = $request->getETags()) { return in_array($etag, $etags) || in_array('*', $etags); } return true; } ... src/EventListener/ConditionalRequestListener.php
$last_modified = $response->getLastModified(); if ($last_modified) { // See if the client has provided the required HTTP headers. $if_modified_since = $request->server->has('HTTP_IF_MODIFIED_SINCE') ? strtotime($request->server- >get('HTTP_IF_MODIFIED_SINCE')) : FALSE; $if_none_match = $request->server->has('HTTP_IF_NONE_MATCH') ? stripslashes($request->server- >get('HTTP_IF_NONE_MATCH')) : FALSE; if ($if_modified_since && $if_none_match // etag must match. && $if_none_match == $response->getEtag() // if-modified-since must match. && $if_modified_since == $last_modified->getTimestamp()) { $response->setStatusCode(304); $response->setContent(NULL); // In the case of a 304 response, certain headers must be sent, and the // remaining may not (see RFC 2616, section 10.3.5). foreach (array_keys($response->headers->all()) as $name) { if (!in_array($name, ['content-location', 'expires', 'cache-control', 'vary'])) { $response->headers->remove($name); } } } } Drupal\page_cache\StackMiddleware\PageCache
✓ Server-side ✓ Standardized ✓ Processed on the “edge”, no in the browser ✓ Generally faster Edge-Side Includes - Sequential - One fails, all fail - Limited implementation in Varnish
public function onRouteMatch(GetResponseEvent $event) { // Don't cache the response if the Dynamic Page Cache request policies are // not met. Store the result in a static keyed by current request, so that // onResponse() does not have to redo the request policy check. $request = $event->getRequest(); $request_policy_result = $this->requestPolicy->check($request); $this->requestPolicyResults[$request] = $request_policy_result; if ($request_policy_result === RequestPolicyInterface::DENY) { return; } // Sets the response for the current route, if cached. $cached = $this->renderCache->get($this->dynamicPageCacheRedirectRenderArray); if ($cached) { $response = $this->renderArrayToResponse($cached); $response->headers->set(self::HEADER, 'HIT'); $event->setResponse($response); } } Drupal\dynamic_page_cache\EventSubscriber\DynamicPageCacheSubscriber
Cache variations HTTP/1.1 200 OK Host: localhost Content-Language: en Content-type: text/html; charset=UTF-8 Hello world output GET / HTTP/1.1 Host: localhost Accept-Language: en, nl, de
# Only allow BAN requests from IP addresses in the 'purge' ACL. if (req.method == "BAN") { # Same ACL check as above: if (!client.ip ~ purge) { return (synth(403, "Not allowed.")); } if (req.http.Purge-Cache-Tags) { ban("obj.http.Purge-Cache-Tags ~ " + req.http.Purge-Cache-Tags); } else { return (synth(403, "Purge-Cache-Tags header missing.")); } # Throw a synthetic page so the request won't go to the backend. return (synth(200, "Ban added.")); }
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