function HttpCache::lock

Locks a Request during the call to the backend.

Return value

bool true if the cache entry can be returned even if it is staled, false otherwise

1 call to HttpCache::lock()

HttpCache::isFreshEnough in vendor/symfony/http-kernel/HttpCache/HttpCache.php

Checks whether the cache entry is "fresh enough" to satisfy the Request.

File

vendor/symfony/http-kernel/HttpCache/HttpCache.php, line 542

Class

HttpCache

Cache provides HTTP caching.

Namespace

Symfony\Component\HttpKernel\HttpCache

Code

protected function lock(Request $request, Response $entry) : bool {
    // 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;
}