function ChainedFastBackend::getMultiple

Overrides CacheBackendInterface::getMultiple

File

core/lib/Drupal/Core/Cache/ChainedFastBackend.php, line 112

Class

ChainedFastBackend

Defines a backend with a fast and a consistent backend chain.

Namespace

Code

public function getMultiple(&$cids, $allow_invalid = FALSE) {
    $cids_copy = $cids;
    $cache = [];
    // If we can determine the time at which the last write to the consistent
    // backend occurred (we might not be able to if it has been recently
    // flushed/restarted), then we can use that to validate items from the fast
    // backend, so try to get those first. Otherwise, we can't assume that
    // anything in the fast backend is valid, so don't even bother fetching
    // from there.
    $last_write_timestamp = $this->getLastWriteTimestamp();
    if ($last_write_timestamp) {
        // Items in the fast backend might be invalid based on their timestamp,
        // but we can't check the timestamp prior to getting the item, which
        // includes unserializing it. However, unserializing an invalid item can
        // throw an exception. For example, a __wakeup() implementation that
        // receives object properties containing references to code or data that
        // no longer exists in the application's current state.
        //
        // Unserializing invalid data, whether it throws an exception or not, is
        // a waste of time, but we only incur it while a cache invalidation has
        // not yet finished propagating to all the fast backend instances.
        //
        // Most cache backend implementations should not wrap their internal
        // get() implementations with a try/catch, because they have no reason to
        // assume that their data is invalid, and doing so would mask
        // unserialization errors of valid data. We do so here, only because the
        // fast backend is non-authoritative, and after discarding its
        // exceptions, we proceed to check the consistent (authoritative) backend
        // and allow exceptions from that to bubble up.
        try {
            $items = $this->fastBackend
                ->getMultiple($cids, $allow_invalid);
        } catch (\Exception) {
            $cids = $cids_copy;
            $items = [];
        }
        // Even if items were successfully fetched from the fast backend, they
        // are potentially invalid if older than the last time the bin was
        // written to in the consistent backend, so only keep ones that aren't.
        foreach ($items as $item) {
            if ($item->created < $last_write_timestamp) {
                $cids[array_search($item->cid, $cids_copy)] = $item->cid;
            }
            else {
                $cache[$item->cid] = $item;
            }
        }
    }
    // If there were any cache entries that were not available in the fast
    // backend, retrieve them from the consistent backend and store them in the
    // fast one.
    if ($cids) {
        foreach ($this->consistentBackend
            ->getMultiple($cids, $allow_invalid) as $item) {
            $cache[$item->cid] = $item;
            $this->fastBackend
                ->set($item->cid, $item->data, $item->expire, $item->tags);
        }
    }
    return $cache;
}