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ResponseCacheStrategy.php
001 <?php
002
003 /*
004 * This file is part of the Symfony package.
005 *
006 * (c) Fabien Potencier <fabien@symfony.com>
007 *
008 * For the full copyright and license information, please view the LICENSE
009 * file that was distributed with this source code.
010 */
011
012 namespace Symfony\Component\HttpKernel\HttpCache;
013
014 use Symfony\Component\HttpFoundation\Response;
015
016 /**
017 * ResponseCacheStrategy knows how to compute the Response cache HTTP header
018 * based on the different response cache headers.
019 *
020 * This implementation changes the master response TTL to the smallest TTL received
021 * or force validation if one of the surrogates has validation cache strategy.
022 *
023 * @author Fabien Potencier <fabien@symfony.com>
024 */
025 class ResponseCacheStrategy implements ResponseCacheStrategyInterface
026 {
027 /**
028 * Cache-Control headers that are sent to the final response if they appear in ANY of the responses.
029 */
030 private static $overrideDirectives = ['private', 'no-cache', 'no-store', 'no-transform', 'must-revalidate', 'proxy-revalidate'];
031
032 /**
033 * Cache-Control headers that are sent to the final response if they appear in ALL of the responses.
034 */
035 private static $inheritDirectives = ['public', 'immutable'];
036
037 private $embeddedResponses = 0;
038 private $isNotCacheableResponseEmbedded = false;
039 private $age = 0;
040 private $flagDirectives = [
041 'no-cache' => null,
042 'no-store' => null,
043 'no-transform' => null,
044 'must-revalidate' => null,
045 'proxy-revalidate' => null,
046 'public' => null,
047 'private' => null,
048 'immutable' => null,
049 ];
050 private $ageDirectives = [
051 'max-age' => null,
052 's-maxage' => null,
053 'expires' => null,
054 ];
055
056 /**
057 * {@inheritdoc}
058 */
059 public function add(Response $response)
060 {
061 ++$this->embeddedResponses;
062
063 foreach (self::$overrideDirectives as $directive) {
064 if ($response->headers->hasCacheControlDirective($directive)) {
065 $this->flagDirectives[$directive] = true;
066 }
067 }
068
069 foreach (self::$inheritDirectives as $directive) {
070 if (false !== $this->flagDirectives[$directive]) {
071 $this->flagDirectives[$directive] = $response->headers->hasCacheControlDirective($directive);
072 }
073 }
074
075 $age = $response->getAge();
076 $this->age = max($this->age, $age);
077
078 if ($this->willMakeFinalResponseUncacheable($response)) {
079 $this->isNotCacheableResponseEmbedded = true;
080
081 return;
082 }
083
084 $this->storeRelativeAgeDirective('max-age', $response->headers->getCacheControlDirective('max-age'), $age);
085 $this->storeRelativeAgeDirective('s-maxage', $response->headers->getCacheControlDirective('s-maxage') ?: $response->headers->getCacheControlDirective('max-age'), $age);
086
087 $expires = $response->getExpires();
088 $expires = null !== $expires ? (int) $expires->format('U') - (int) $response->getDate()->format('U') : null;
089 $this->storeRelativeAgeDirective('expires', $expires >= 0 ? $expires : null, 0);
090 }
091
092 /**
093 * {@inheritdoc}
094 */
095 public function update(Response $response)
096 {
097 // if we have no embedded Response, do nothing
098 if (0 === $this->embeddedResponses) {
099 return;
100 }
101
102 // Remove validation related headers of the master response,
103 // because some of the response content comes from at least
104 // one embedded response (which likely has a different caching strategy).
105 $response->setEtag(null);
106 $response->setLastModified(null);
107
108 $this->add($response);
109
110 $response->headers->set('Age', $this->age);
111
112 if ($this->isNotCacheableResponseEmbedded) {
113 if ($this->flagDirectives['no-store']) {
114 $response->headers->set('Cache-Control', 'no-cache, no-store, must-revalidate');
115 } else {
116 $response->headers->set('Cache-Control', 'no-cache, must-revalidate');
117 }
118
119 return;
120 }
121
122 $flags = array_filter($this->flagDirectives);
123
124 if (isset($flags['must-revalidate'])) {
125 $flags['no-cache'] = true;
126 }
127
128 $response->headers->set('Cache-Control', implode(', ', array_keys($flags)));
129
130 $maxAge = null;
131
132 if (is_numeric($this->ageDirectives['max-age'])) {
133 $maxAge = $this->ageDirectives['max-age'] + $this->age;
134 $response->headers->addCacheControlDirective('max-age', $maxAge);
135 }
136
137 if (is_numeric($this->ageDirectives['s-maxage'])) {
138 $sMaxage = $this->ageDirectives['s-maxage'] + $this->age;
139
140 if ($maxAge !== $sMaxage) {
141 $response->headers->addCacheControlDirective('s-maxage', $sMaxage);
142 }
143 }
144
145 if (is_numeric($this->ageDirectives['expires'])) {
146 $date = clone $response->getDate();
147 $date->modify('+'.($this->ageDirectives['expires'] + $this->age).' seconds');
148 $response->setExpires($date);
149 }
150 }
151
152 /**
153 * RFC2616, Section 13.4.
154 *
155 * @see https://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html#sec13.4
156 *
157 * @return bool
158 */
159 private function willMakeFinalResponseUncacheable(Response $response)
160 {
161 // RFC2616: A response received with a status code of 200, 203, 300, 301 or 410
162 // MAY be stored by a cache […] unless a cache-control directive prohibits caching.
163 if ($response->headers->hasCacheControlDirective('no-cache')
164 || $response->headers->getCacheControlDirective('no-store')
165 ) {
166 return true;
167 }
168
169 // Last-Modified and Etag headers cannot be merged, they render the response uncacheable
170 // by default (except if the response also has max-age etc.).
171 if (\in_array($response->getStatusCode(), [200, 203, 300, 301, 410])
172 && null === $response->getLastModified()
173 && null === $response->getEtag()
174 ) {
175 return false;
176 }
177
178 // RFC2616: A response received with any other status code (e.g. status codes 302 and 307)
179 // MUST NOT be returned in a reply to a subsequent request unless there are
180 // cache-control directives or another header(s) that explicitly allow it.
181 $cacheControl = ['max-age', 's-maxage', 'must-revalidate', 'proxy-revalidate', 'public', 'private'];
182 foreach ($cacheControl as $key) {
183 if ($response->headers->hasCacheControlDirective($key)) {
184 return false;
185 }
186 }
187
188 if ($response->headers->has('Expires')) {
189 return false;
190 }
191
192 return true;
193 }
194
195 /**
196 * Store lowest max-age/s-maxage/expires for the final response.
197 *
198 * The response might have been stored in cache a while ago. To keep things comparable,
199 * we have to subtract the age so that the value is normalized for an age of 0.
200 *
201 * If the value is lower than the currently stored value, we update the value, to keep a rolling
202 * minimal value of each instruction. If the value is NULL, the directive will not be set on the final response.
203 *
204 * @param string $directive
205 * @param int|null $value
206 * @param int $age
207 */
208 private function storeRelativeAgeDirective($directive, $value, $age)
209 {
210 if (null === $value) {
211 $this->ageDirectives[$directive] = false;
212 }
213
214 if (false !== $this->ageDirectives[$directive]) {
215 $value -= $age;
216 $this->ageDirectives[$directive] = null !== $this->ageDirectives[$directive] ? min($this->ageDirectives[$directive], $value) : $value;
217 }
218 }
219 }
220