Try waiting a few minutes and reloading.
(Cannot access the database)
Backtrace:
#0 /var/www/html/includes/libs/rdbms/loadbalancer/LoadBalancer.php(956): Wikimedia\Rdbms\LoadBalancer->reportConnectionError() #1 /var/www/html/includes/libs/rdbms/loadbalancer/LoadBalancer.php(928): Wikimedia\Rdbms\LoadBalancer->getServerConnection() #2 /var/www/html/includes/libs/rdbms/loadbalancer/LoadBalancer.php(1086): Wikimedia\Rdbms\LoadBalancer->getConnection() #3 /var/www/html/includes/GlobalFunctions.php(2208): Wikimedia\Rdbms\LoadBalancer->getMaintenanceConnectionRef() #4 /var/www/html/includes/Title.php(516): wfGetDB() #5 /var/www/html/includes/MediaWiki.php(87): Title::newFromID() #6 /var/www/html/includes/MediaWiki.php(162): MediaWiki->parseTitle() #7 /var/www/html/includes/MediaWiki.php(870): MediaWiki->getTitle() #8 /var/www/html/includes/MediaWiki.php(563): MediaWiki->main() #9 /var/www/html/index.php(53): MediaWiki->run() #10 /var/www/html/index.php(46): wfIndexMain() #11 {main}