/**
* 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 Symfony\Components\HttpKernel\Request $request A Request instance
*
* @return Symfony\Components\HttpKernel\Response A Response instance
*/
protected function lookup(Request $request)
{
if ($this->options['allow_reload'] && $request->isNoCache()) {
$this->record($request, 'reload');
return $this->fetch($request);
}
try {
$entry = $this->store->lookup($request);
} catch (\Exception $e) {
$this->record($request, 'lookup-failed');
if ($this->options['debug']) {
throw $e;
}
return $this->pass($request);
}
if (null === $entry) {
$this->record($request, 'miss');
return $this->fetch($request);
}
if (!$this->isFreshEnough($request, $entry)) {
$this->record($request, 'stale');
return $this->validate($request, $entry);
}
$this->record($request, 'fresh');
$entry->headers->set('Age', $entry->getAge());
return $entry;
}
