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<?php
namespace Guzzle\Plugin\Cache;
use Guzzle\Http\Message\RequestInterface;
use Guzzle\Http\Message\Response;
use Guzzle\Http\Exception\BadResponseException;
/**
* Default revalidation strategy
*/
class DefaultRevalidation implements RevalidationInterface
{
/** @var CacheStorageInterface Cache object storing cache data */
protected $storage;
/** @var CanCacheStrategyInterface */
protected $canCache;
/**
* @param CacheStorageInterface $cache Cache storage
* @param CanCacheStrategyInterface $canCache Determines if a message can be cached
*/
public function __construct(CacheStorageInterface $cache, CanCacheStrategyInterface $canCache = null)
{
$this->storage = $cache;
$this->canCache = $canCache ?: new DefaultCanCacheStrategy();
}
public function revalidate(RequestInterface $request, Response $response)
{
try {
$revalidate = $this->createRevalidationRequest($request, $response);
$validateResponse = $revalidate->send();
if ($validateResponse->getStatusCode() == 200) {
return $this->handle200Response($request, $validateResponse);
} elseif ($validateResponse->getStatusCode() == 304) {
return $this->handle304Response($request, $validateResponse, $response);
}
} catch (BadResponseException $e) {
$this->handleBadResponse($e);
}
// Other exceptions encountered in the revalidation request are ignored
// in hopes that sending a request to the origin server will fix it
return false;
}
public function shouldRevalidate(RequestInterface $request, Response $response)
{
if ($request->getMethod() != RequestInterface::GET) {
return false;
}
$reqCache = $request->getHeader('Cache-Control');
$resCache = $response->getHeader('Cache-Control');
$revalidate = $request->getHeader('Pragma') == 'no-cache' ||
($reqCache && ($reqCache->hasDirective('no-cache') || $reqCache->hasDirective('must-revalidate'))) ||
($resCache && ($resCache->hasDirective('no-cache') || $resCache->hasDirective('must-revalidate')));
// Use the strong ETag validator if available and the response contains no Cache-Control directive
if (!$revalidate && !$resCache && $response->hasHeader('ETag')) {
$revalidate = true;
}
return $revalidate;
}
/**
* Handles a bad response when attempting to revalidate
*
* @param BadResponseException $e Exception encountered
*
* @throws BadResponseException
*/
protected function handleBadResponse(BadResponseException $e)
{
// 404 errors mean the resource no longer exists, so remove from
// cache, and prevent an additional request by throwing the exception
if ($e->getResponse()->getStatusCode() == 404) {
$this->storage->delete($e->getRequest());
throw $e;
}
}
/**
* Creates a request to use for revalidation
*
* @param RequestInterface $request Request
* @param Response $response Response to revalidate
*
* @return RequestInterface returns a revalidation request
*/
protected function createRevalidationRequest(RequestInterface $request, Response $response)
{
$revalidate = clone $request;
$revalidate->removeHeader('Pragma')->removeHeader('Cache-Control');
if ($response->getLastModified()) {
$revalidate->setHeader('If-Modified-Since', $response->getLastModified());
}
if ($response->getEtag()) {
$revalidate->setHeader('If-None-Match', $response->getEtag());
}
// Remove any cache plugins that might be on the request to prevent infinite recursive revalidations
$dispatcher = $revalidate->getEventDispatcher();
foreach ($dispatcher->getListeners() as $eventName => $listeners) {
foreach ($listeners as $listener) {
if (is_array($listener) && $listener[0] instanceof CachePlugin) {
$dispatcher->removeListener($eventName, $listener);
}
}
}
return $revalidate;
}
/**
* Handles a 200 response response from revalidating. The server does not support validation, so use this response.
*
* @param RequestInterface $request Request that was sent
* @param Response $validateResponse Response received
*
* @return bool Returns true if valid, false if invalid
*/
protected function handle200Response(RequestInterface $request, Response $validateResponse)
{
$request->setResponse($validateResponse);
if ($this->canCache->canCacheResponse($validateResponse)) {
$this->storage->cache($request, $validateResponse);
}
return false;
}
/**
* Handle a 304 response and ensure that it is still valid
*
* @param RequestInterface $request Request that was sent
* @param Response $validateResponse Response received
* @param Response $response Original cached response
*
* @return bool Returns true if valid, false if invalid
*/
protected function handle304Response(RequestInterface $request, Response $validateResponse, Response $response)
{
static $replaceHeaders = array('Date', 'Expires', 'Cache-Control', 'ETag', 'Last-Modified');
// Make sure that this response has the same ETag
if ($validateResponse->getEtag() != $response->getEtag()) {
return false;
}
// Replace cached headers with any of these headers from the
// origin server that might be more up to date
$modified = false;
foreach ($replaceHeaders as $name) {
if ($validateResponse->hasHeader($name)) {
$modified = true;
$response->setHeader($name, $validateResponse->getHeader($name));
}
}
// Store the updated response in cache
if ($modified && $this->canCache->canCacheResponse($response)) {
$this->storage->cache($request, $response);
}
return true;
}
}
|
