+
+ $cache = $this->loadFromDB( $code );
+ $this->mCache[$code] = $cache;
+ $success = true;
+ $saveSuccess = $this->saveToCaches( $cache, 'all', $code );
+
+ # Unlock
+ ScopedCallback::consume( $mainUnlocker );
+ ScopedCallback::consume( $statusUnlocker );
+
+ if ( !$saveSuccess ) {
+ # Cache save has failed.
+ # There are two main scenarios where this could be a problem:
+ #
+ # - The cache is more than the maximum size (typically
+ # 1MB compressed).
+ #
+ # - Memcached has no space remaining in the relevant slab
+ # class. This is unlikely with recent versions of
+ # memcached.
+ #
+ # Either way, if there is a local cache, nothing bad will
+ # happen. If there is no local cache, disabling the message
+ # cache for all requests avoids incurring a loadFromDB()
+ # overhead on every request, and thus saves the wiki from
+ # complete downtime under moderate traffic conditions.
+ if ( !$wgUseLocalMessageCache ) {
+ $this->mMemc->set( $statusKey, 'error', 60 * 5 );
+ $where[] = 'could not save cache, disabled globally for 5 minutes';
+ } else {
+ $where[] = "could not save global cache";
+ }
+ }
+
+ # Load from DB complete, no need to retry
+ break;
+ } elseif ( $staleCache ) {
+ # Use the stale cache while some other thread constructs the new one
+ $where[] = 'using stale cache';
+ $this->mCache[$code] = $staleCache;
+ $success = true;
+ break;
+ } elseif ( $failedAttempts > 0 ) {
+ # Already retried once, still failed, so don't do another lock/unlock cycle
+ # This case will typically be hit if memcached is down, or if
+ # loadFromDB() takes longer than MSG_WAIT_TIMEOUT
+ $where[] = "could not acquire status key.";
+ break;