Try waiting a few minutes and reloading.
(Cannot access the database: Too many connections (localhost:3306))
Backtrace:
#0 /var/www/mediawiki-1.30.0/includes/libs/rdbms/loadbalancer/LoadBalancer.php(1028): Wikimedia\Rdbms\Database->reportConnectionError('Too many connec...') #1 /var/www/mediawiki-1.30.0/includes/libs/rdbms/loadbalancer/LoadBalancer.php(670): Wikimedia\Rdbms\LoadBalancer->reportConnectionError() #2 /var/www/mediawiki-1.30.0/includes/GlobalFunctions.php(2858): Wikimedia\Rdbms\LoadBalancer->getConnection(0, Array, false) #3 /var/www/mediawiki-1.30.0/includes/Revision.php(330): wfGetDB(-1) #4 /var/www/mediawiki-1.30.0/includes/Revision.php(117): Revision::newFromConds(Array, 0) #5 /var/www/mediawiki-1.30.0/includes/MediaWiki.php(109): Revision::newFromId(17004) #6 /var/www/mediawiki-1.30.0/includes/MediaWiki.php(140): MediaWiki->parseTitle() #7 /var/www/mediawiki-1.30.0/includes/MediaWiki.php(767): MediaWiki->getTitle() #8 /var/www/mediawiki-1.30.0/includes/MediaWiki.php(523): MediaWiki->main() #9 /var/www/mediawiki-1.30.0/index.php(43): MediaWiki->run() #10 {main}