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Edit File : HttpCache.php \| Size : 25.06 KB
<?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. / / * This code is partially based on the Rack-Cache library by Ryan Tomayko, * which is released under the MIT license. * (based on commit 02d2b48d75bcb63cf1c0c7149c077ad256542801) / namespace Symfony\Component\HttpKernel\HttpCache; use Symfony\Component\HttpFoundation\Request; use Symfony\Component\HttpFoundation\Response; use Symfony\Component\HttpKernel\HttpKernelInterface; use Symfony\Component\HttpKernel\TerminableInterface; /* * Cache provides HTTP caching. * * @author Fabien Potencier <fabien@symfony.com> / class HttpCache implements HttpKernelInterface, TerminableInterface { private $kernel; private $store; private $request; private $surrogate; private $surrogateCacheStrategy; private $options = []; private $traces = []; /* * Constructor. * * The available options are: * * * debug If true, exceptions are thrown when things go wrong. Otherwise, the cache * will try to carry on and deliver a meaningful response. * * * trace_level May be one of 'none', 'short' and 'full'. For 'short', a concise trace of the * master request will be added as an HTTP header. 'full' will add traces for all * requests (including ESI subrequests). (default: 'full' if in debug; 'none' otherwise) * * * trace_header Header name to use for traces. (default: X-Symfony-Cache) * * * 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). / public function __construct(HttpKernelInterface $kernel, StoreInterface $store, SurrogateInterface $surrogate = null, array $options = []) { $this->store = $store; $this->kernel = $kernel; $this->surrogate = $surrogate; // needed in case there is a fatal error because the backend is too slow to respond register_shutdown_function([$this->store, 'cleanup']); $this->options = array_merge([ 'debug' => false, 'default_ttl' => 0, 'private_headers' => ['Authorization', 'Cookie'], 'allow_reload' => false, 'allow_revalidate' => false, 'stale_while_revalidate' => 2, 'stale_if_error' => 60, 'trace_level' => 'none', 'trace_header' => 'X-Symfony-Cache', ], $options); if (!isset($options['trace_level'])) { $this->options['trace_level'] = $this->options['debug'] ? 'full' : 'none'; } } /* * Gets the current store. * * @return StoreInterface 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; } private function addTraces(Response $response) { $traceString = null; if ('full' === $this->options['trace_level']) { $traceString = $this->getLog(); } if ('short' === $this->options['trace_level'] && $masterId = array_key_first($this->traces)) { $traceString = implode('/', $this->traces[$masterId]); } if (null !== $traceString) { $response->headers->add([$this->options['trace_header'] => $traceString]); } } /* * Returns a log message for the events of the last request processing. * * @return string A log message / public function getLog() { $log = []; foreach ($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 Surrogate instance. * * @return SurrogateInterface A Surrogate instance * * @throws \LogicException / public function getSurrogate() { return $this->surrogate; } /* * {@inheritdoc} / 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 = []; // Keep a clone of the original request for surrogates so they can access it. // We must clone here to get a separate instance because the application will modify the request during // the application flow (we know it always does because we do ourselves by setting REMOTE_ADDR to 127.0.0.1 // and adding the X-Forwarded-For header, see HttpCache::forward()). $this->request = clone $request; if (null !== $this->surrogate) { $this->surrogateCacheStrategy = $this->surrogate->createCacheStrategy(); } } $this->traces[$this->getTraceKey($request)] = []; if (!$request->isMethodSafe()) { $response = $this->invalidate($request, $catch); } elseif ($request->headers->has('expect') \|\| !$request->isMethodCacheable()) { $response = $this->pass($request, $catch); } elseif ($this->options['allow_reload'] && $request->isNoCache()) { / If allow_reload is configured and the client requests "Cache-Control: no-cache", reload the cache by fetching a fresh response and caching it (if possible). / $this->record($request, 'reload'); $response = $this->fetch($request, $catch); } else { $response = $this->lookup($request, $catch); } $this->restoreResponseBody($request, $response); if (HttpKernelInterface::MASTER_REQUEST === $type) { $this->addTraces($response); } if (null !== $this->surrogate) { if (HttpKernelInterface::MASTER_REQUEST === $type) { $this->surrogateCacheStrategy->update($response); } else { $this->surrogateCacheStrategy->add($response); } } $response->prepare($request); $response->isNotModified($request); return $response; } /* * {@inheritdoc} / 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 bool $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 bool $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); // As per the RFC, invalidate Location and Content-Location URLs if present foreach (['Location', 'Content-Location'] as $header) { if ($uri = $response->headers->get($header)) { $subRequest = Request::create($uri, 'get', [], [], [], $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 bool $catch Whether to process exceptions * * @return Response A Response instance * * @throws \Exception / protected function lookup(Request $request, $catch = false) { 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, $catch); } if ($entry->headers->hasCacheControlDirective('no-cache')) { 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 bool $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 if ('HEAD' === $request->getMethod()) { $subRequest->setMethod('GET'); } // add our cached last-modified validator if ($entry->headers->has('Last-Modified')) { $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 = $entry->getEtag() ? [$entry->getEtag()] : []; $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 (['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; } /* * Unconditionally fetches a fresh response from the backend and * stores it in the cache if is cacheable. * * @param bool $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 if ('HEAD' === $request->getMethod()) { $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, $catch); if ($response->isCacheable()) { $this->store($request, $response); } return $response; } /* * Forwards the Request to the backend and returns the Response. * * All backend requests (cache passes, fetches, cache validations) * run through this method. * * @param bool $catch Whether to catch exceptions or not * @param Response\|null $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->surrogate) { $this->surrogate->addSurrogateCapability($request); } // always a "master" request (as the real master request can be in cache) $response = SubRequestHandler::handle($this->kernel, $request, HttpKernelInterface::MASTER_REQUEST, $catch); / * Support stale-if-error given on Responses or as a config option. * RFC 7234 summarizes in Section 4.2.4 (but also mentions with the individual * Cache-Control directives) that * * A cache MUST NOT generate a stale response if it is prohibited by an * explicit in-protocol directive (e.g., by a "no-store" or "no-cache" * cache directive, a "must-revalidate" cache-response-directive, or an * applicable "s-maxage" or "proxy-revalidate" cache-response-directive; * see Section 5.2.2). * * https://tools.ietf.org/html/rfc7234#section-4.2.4 * * We deviate from this in one detail, namely that we do serve entries in the * stale-if-error case even if they have a `s-maxage` Cache-Control directive. / if (null !== $entry && \in_array($response->getStatusCode(), [500, 502, 503, 504]) && !$entry->headers->hasCacheControlDirective('no-cache') && !$entry->mustRevalidate() ) { if (null === $age = $entry->headers->getCacheControlDirective('stale-if-error')) { $age = $this->options['stale_if_error']; } / * stale-if-error gives the (extra) time that the Response may be used after it has become stale. * So we compare the time the $entry has been sitting in the cache already with the * time it was fresh plus the allowed grace period. / if ($entry->getAge() <= $entry->getMaxAge() + $age) { $this->record($request, 'stale-if-error'); return $entry; } } / RFC 7231 Sect. 7.1.1.2 says that a server that does not have a reasonably accurate clock MUST NOT send a "Date" header, although it MUST send one in most other cases except for 1xx or 5xx responses where it MAY do so. Anyway, a client that received a message without a "Date" header MUST add it. / if (!$response->headers->has('Date')) { $response->setDate(\DateTime::createFromFormat('U', time())); } $this->processResponseBody($request, $response); if ($this->isPrivateRequest($request) && !$response->headers->hasCacheControlDirective('public')) { $response->setPrivate(); } elseif ($this->options['default_ttl'] > 0 && null === $response->getTtl() && !$response->headers->getCacheControlDirective('must-revalidate')) { $response->setTtl($this->options['default_ttl']); } return $response; } /* * Checks whether the cache entry is "fresh enough" to satisfy the Request. * * @return bool 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. * * @return bool 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); if (true === $lock) { // we have the lock, call the backend return false; } // there is already another process calling the backend // May we serve a stale response? if ($this->mayServeStaleWhileRevalidate($entry)) { $this->record($request, 'stale-while-revalidate'); return true; } // wait for the lock to be released if ($this->waitForLock($request)) { // 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; } /* * Writes the Response to the cache. * * @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. / private function restoreResponseBody(Request $request, Response $response) { if ($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 ($response->headers->has('X-Body-File')) { // Response does not include possibly dynamic content (ESI, SSI), so we need // not handle the content for HEAD requests if (!$request->isMethod('HEAD')) { $response->setContent(file_get_contents($response->headers->get('X-Body-File'))); } } else { return; } $response->headers->remove('X-Body-File'); } protected function processResponseBody(Request $request, Response $response) { if (null !== $this->surrogate && $this->surrogate->needsParsing($response)) { $this->surrogate->process($request, $response); } } /* * Checks if the Request includes authorization or other sensitive information * that should cause the Response to be considered private by default. / private function isPrivateRequest(Request $request): bool { foreach ($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. / private function record(Request $request, string $event) { $this->traces[$this->getTraceKey($request)][] = $event; } /* * Calculates the key we use in the "trace" array for a given request. / private function getTraceKey(Request $request): string { $path = $request->getPathInfo(); if ($qs = $request->getQueryString()) { $path .= '?'.$qs; } return $request->getMethod().' '.$path; } /* * Checks whether the given (cached) response may be served as "stale" when a revalidation * is currently in progress. / private function mayServeStaleWhileRevalidate(Response $entry): bool { $timeout = $entry->headers->getCacheControlDirective('stale-while-revalidate'); if (null === $timeout) { $timeout = $this->options['stale_while_revalidate']; } return abs($entry->getTtl()) < $timeout; } /* * Waits for the store to release a locked entry. */ private function waitForLock(Request $request): bool { $wait = 0; while ($this->store->isLocked($request) && $wait < 100) { usleep(50000); ++$wait; } return $wait < 100; } } Back

Edit File : HttpCache.php | Size : 25.06 KB

<?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.
 */

/*
 * This code is partially based on the Rack-Cache library by Ryan Tomayko,
 * which is released under the MIT license.
 * (based on commit 02d2b48d75bcb63cf1c0c7149c077ad256542801)
 */

namespace Symfony\Component\HttpKernel\HttpCache;

use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\HttpKernelInterface;
use Symfony\Component\HttpKernel\TerminableInterface;

/**
 * Cache provides HTTP caching.
 *
 * @author Fabien Potencier <fabien@symfony.com>
 */
class HttpCache implements HttpKernelInterface, TerminableInterface
{
    private $kernel;
    private $store;
    private $request;
    private $surrogate;
    private $surrogateCacheStrategy;
    private $options = [];
    private $traces = [];

/**
     * Constructor.
     *
     * The available options are:
     *
     *   * debug                  If true, exceptions are thrown when things go wrong. Otherwise, the cache
     *                            will try to carry on and deliver a meaningful response.
     *
     *   * trace_level            May be one of 'none', 'short' and 'full'. For 'short', a concise trace of the
     *                            master request will be added as an HTTP header. 'full' will add traces for all
     *                            requests (including ESI subrequests). (default: 'full' if in debug; 'none' otherwise)
     *
     *   * trace_header           Header name to use for traces. (default: X-Symfony-Cache)
     *
     *   * 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).
     */
    public function __construct(HttpKernelInterface $kernel, StoreInterface $store, SurrogateInterface $surrogate = null, array $options = [])
    {
        $this->store = $store;
        $this->kernel = $kernel;
        $this->surrogate = $surrogate;

// needed in case there is a fatal error because the backend is too slow to respond
        register_shutdown_function([$this->store, 'cleanup']);

$this->options = array_merge([
            'debug' => false,
            'default_ttl' => 0,
            'private_headers' => ['Authorization', 'Cookie'],
            'allow_reload' => false,
            'allow_revalidate' => false,
            'stale_while_revalidate' => 2,
            'stale_if_error' => 60,
            'trace_level' => 'none',
            'trace_header' => 'X-Symfony-Cache',
        ], $options);

if (!isset($options['trace_level'])) {
            $this->options['trace_level'] = $this->options['debug'] ? 'full' : 'none';
        }
    }

/**
     * Gets the current store.
     *
     * @return StoreInterface 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;
    }

private function addTraces(Response $response)
    {
        $traceString = null;

if ('full' === $this->options['trace_level']) {
            $traceString = $this->getLog();
        }

if ('short' === $this->options['trace_level'] && $masterId = array_key_first($this->traces)) {
            $traceString = implode('/', $this->traces[$masterId]);
        }

if (null !== $traceString) {
            $response->headers->add([$this->options['trace_header'] => $traceString]);
        }
    }

/**
     * Returns a log message for the events of the last request processing.
     *
     * @return string A log message
     */
    public function getLog()
    {
        $log = [];
        foreach ($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 Surrogate instance.
     *
     * @return SurrogateInterface A Surrogate instance
     *
     * @throws \LogicException
     */
    public function getSurrogate()
    {
        return $this->surrogate;
    }

/**
     * {@inheritdoc}
     */
    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 = [];
            // Keep a clone of the original request for surrogates so they can access it.
            // We must clone here to get a separate instance because the application will modify the request during
            // the application flow (we know it always does because we do ourselves by setting REMOTE_ADDR to 127.0.0.1
            // and adding the X-Forwarded-For header, see HttpCache::forward()).
            $this->request = clone $request;
            if (null !== $this->surrogate) {
                $this->surrogateCacheStrategy = $this->surrogate->createCacheStrategy();
            }
        }

$this->traces[$this->getTraceKey($request)] = [];

if (!$request->isMethodSafe()) {
            $response = $this->invalidate($request, $catch);
        } elseif ($request->headers->has('expect') || !$request->isMethodCacheable()) {
            $response = $this->pass($request, $catch);
        } elseif ($this->options['allow_reload'] && $request->isNoCache()) {
            /*
                If allow_reload is configured and the client requests "Cache-Control: no-cache",
                reload the cache by fetching a fresh response and caching it (if possible).
            */
            $this->record($request, 'reload');
            $response = $this->fetch($request, $catch);
        } else {
            $response = $this->lookup($request, $catch);
        }

$this->restoreResponseBody($request, $response);

if (HttpKernelInterface::MASTER_REQUEST === $type) {
            $this->addTraces($response);
        }

if (null !== $this->surrogate) {
            if (HttpKernelInterface::MASTER_REQUEST === $type) {
                $this->surrogateCacheStrategy->update($response);
            } else {
                $this->surrogateCacheStrategy->add($response);
            }
        }

$response->prepare($request);

$response->isNotModified($request);

return $response;
    }

/**
     * {@inheritdoc}
     */
    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 bool $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 bool $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);

// As per the RFC, invalidate Location and Content-Location URLs if present
                foreach (['Location', 'Content-Location'] as $header) {
                    if ($uri = $response->headers->get($header)) {
                        $subRequest = Request::create($uri, 'get', [], [], [], $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 bool $catch Whether to process exceptions
     *
     * @return Response A Response instance
     *
     * @throws \Exception
     */
    protected function lookup(Request $request, $catch = false)
    {
        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);
        }

if ($entry->headers->hasCacheControlDirective('no-cache')) {
            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 bool $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
        if ('HEAD' === $request->getMethod()) {
            $subRequest->setMethod('GET');
        }

// add our cached last-modified validator
        if ($entry->headers->has('Last-Modified')) {
            $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 = $entry->getEtag() ? [$entry->getEtag()] : [];
        $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 (['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;
    }

/**
     * Unconditionally fetches a fresh response from the backend and
     * stores it in the cache if is cacheable.
     *
     * @param bool $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
        if ('HEAD' === $request->getMethod()) {
            $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 ($response->isCacheable()) {
            $this->store($request, $response);
        }

return $response;
    }

/**
     * Forwards the Request to the backend and returns the Response.
     *
     * All backend requests (cache passes, fetches, cache validations)
     * run through this method.
     *
     * @param bool          $catch Whether to catch exceptions or not
     * @param Response|null $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->surrogate) {
            $this->surrogate->addSurrogateCapability($request);
        }

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

/*
         * Support stale-if-error given on Responses or as a config option.
         * RFC 7234 summarizes in Section 4.2.4 (but also mentions with the individual
         * Cache-Control directives) that
         *
         *      A cache MUST NOT generate a stale response if it is prohibited by an
         *      explicit in-protocol directive (e.g., by a "no-store" or "no-cache"
         *      cache directive, a "must-revalidate" cache-response-directive, or an
         *      applicable "s-maxage" or "proxy-revalidate" cache-response-directive;
         *      see Section 5.2.2).
         *
         * https://tools.ietf.org/html/rfc7234#section-4.2.4
         *
         * We deviate from this in one detail, namely that we *do* serve entries in the
         * stale-if-error case even if they have a `s-maxage` Cache-Control directive.
         */
        if (null !== $entry
            && \in_array($response->getStatusCode(), [500, 502, 503, 504])
            && !$entry->headers->hasCacheControlDirective('no-cache')
            && !$entry->mustRevalidate()
        ) {
            if (null === $age = $entry->headers->getCacheControlDirective('stale-if-error')) {
                $age = $this->options['stale_if_error'];
            }

/*
             * stale-if-error gives the (extra) time that the Response may be used *after* it has become stale.
             * So we compare the time the $entry has been sitting in the cache already with the
             * time it was fresh plus the allowed grace period.
             */
            if ($entry->getAge() <= $entry->getMaxAge() + $age) {
                $this->record($request, 'stale-if-error');

return $entry;
            }
        }

/*
            RFC 7231 Sect. 7.1.1.2 says that a server that does not have a reasonably accurate
            clock MUST NOT send a "Date" header, although it MUST send one in most other cases
            except for 1xx or 5xx responses where it MAY do so.

Anyway, a client that received a message without a "Date" header MUST add it.
        */
        if (!$response->headers->has('Date')) {
            $response->setDate(\DateTime::createFromFormat('U', time()));
        }

$this->processResponseBody($request, $response);

if ($this->isPrivateRequest($request) && !$response->headers->hasCacheControlDirective('public')) {
            $response->setPrivate();
        } elseif ($this->options['default_ttl'] > 0 && null === $response->getTtl() && !$response->headers->getCacheControlDirective('must-revalidate')) {
            $response->setTtl($this->options['default_ttl']);
        }

return $response;
    }

/**
     * Checks whether the cache entry is "fresh enough" to satisfy the Request.
     *
     * @return bool 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.
     *
     * @return bool 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);

if (true === $lock) {
            // we have the lock, call the backend
            return false;
        }

// there is already another process calling the backend

// May we serve a stale response?
        if ($this->mayServeStaleWhileRevalidate($entry)) {
            $this->record($request, 'stale-while-revalidate');

return true;
        }

// wait for the lock to be released
        if ($this->waitForLock($request)) {
            // 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;
    }

/**
     * Writes the Response to the cache.
     *
     * @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.
     */
    private function restoreResponseBody(Request $request, Response $response)
    {
        if ($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 ($response->headers->has('X-Body-File')) {
            // Response does not include possibly dynamic content (ESI, SSI), so we need
            // not handle the content for HEAD requests
            if (!$request->isMethod('HEAD')) {
                $response->setContent(file_get_contents($response->headers->get('X-Body-File')));
            }
        } else {
            return;
        }

$response->headers->remove('X-Body-File');
    }

protected function processResponseBody(Request $request, Response $response)
    {
        if (null !== $this->surrogate && $this->surrogate->needsParsing($response)) {
            $this->surrogate->process($request, $response);
        }
    }

/**
     * Checks if the Request includes authorization or other sensitive information
     * that should cause the Response to be considered private by default.
     */
    private function isPrivateRequest(Request $request): bool
    {
        foreach ($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.
     */
    private function record(Request $request, string $event)
    {
        $this->traces[$this->getTraceKey($request)][] = $event;
    }

/**
     * Calculates the key we use in the "trace" array for a given request.
     */
    private function getTraceKey(Request $request): string
    {
        $path = $request->getPathInfo();
        if ($qs = $request->getQueryString()) {
            $path .= '?'.$qs;
        }

return $request->getMethod().' '.$path;
    }

/**
     * Checks whether the given (cached) response may be served as "stale" when a revalidation
     * is currently in progress.
     */
    private function mayServeStaleWhileRevalidate(Response $entry): bool
    {
        $timeout = $entry->headers->getCacheControlDirective('stale-while-revalidate');

if (null === $timeout) {
            $timeout = $this->options['stale_while_revalidate'];
        }

return abs($entry->getTtl()) < $timeout;
    }

/**
     * Waits for the store to release a locked entry.
     */
    private function waitForLock(Request $request): bool
    {
        $wait = 0;
        while ($this->store->isLocked($request) && $wait < 100) {
            usleep(50000);
            ++$wait;
        }

return $wait < 100;
    }
}

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