MediaWiki internal error.

Original exception: [44567c18891776468889627e] /w/index.php?limit=500&hideredirs=1 Error from line 640 of /var/www/liandri/w/includes/exception/MWExceptionHandler.php: Class 'FormatJson' not found
Backtrace:
#0 /var/www/liandri/w/includes/exception/MWExceptionHandler.php(197): MWExceptionHandler::logError()
#1 /var/www/liandri/w/includes/AutoLoader.php(81): MWExceptionHandler::handleError()
#2 /var/www/liandri/w/includes/AutoLoader.php(81): require()
#3 [internal function]: AutoLoader::autoload()
#4 /var/www/liandri/w/includes/exception/MWExceptionHandler.php(604): spl_autoload_call()
#5 /var/www/liandri/w/includes/exception/MWExceptionHandler.php(111): MWExceptionHandler::logException()
#6 /var/www/liandri/w/includes/exception/MWExceptionHandler.php(129): MWExceptionHandler::rollbackMasterChangesAndLog()
#7 /var/www/liandri/w/includes/MediaWiki.php(551): MWExceptionHandler::handleException()
#8 /var/www/liandri/w/index.php(43): MediaWiki->run()
#9 {main}

Exception caught inside exception handler: [44567c18891776468889627e] /w/index.php?limit=500&hideredirs=1 Wikimedia\Rdbms\DBConnectionError from line 769 of /var/www/liandri/w/includes/libs/rdbms/database/Database.php: Cannot access the database: Too many connections (mariadb)
Backtrace:
#0 /var/www/liandri/w/includes/libs/rdbms/loadbalancer/LoadBalancer.php(995): Wikimedia\Rdbms\Database->reportConnectionError()
#1 /var/www/liandri/w/includes/libs/rdbms/loadbalancer/LoadBalancer.php(666): Wikimedia\Rdbms\LoadBalancer->reportConnectionError()
#2 /var/www/liandri/w/includes/GlobalFunctions.php(3062): Wikimedia\Rdbms\LoadBalancer->getConnection()
#3 /var/www/liandri/w/includes/cache/MessageCache.php(461): wfGetDB()
#4 /var/www/liandri/w/includes/cache/MessageCache.php(420): MessageCache->loadFromDB()
#5 /var/www/liandri/w/includes/cache/MessageCache.php(344): MessageCache->loadFromDBWithLock()
#6 /var/www/liandri/w/includes/cache/MessageCache.php(976): MessageCache->load()
#7 /var/www/liandri/w/includes/cache/MessageCache.php(904): MessageCache->getMsgFromNamespace()
#8 /var/www/liandri/w/includes/cache/MessageCache.php(873): MessageCache->getMessageForLang()
#9 /var/www/liandri/w/includes/cache/MessageCache.php(813): MessageCache->getMessageFromFallbackChain()
#10 /var/www/liandri/w/includes/Message.php(1257): MessageCache->get()
#11 /var/www/liandri/w/includes/Message.php(842): Message->fetchMessage()
#12 /var/www/liandri/w/includes/Message.php(934): Message->toString()
#13 /var/www/liandri/w/includes/OutputPage.php(936): Message->text()
#14 /var/www/liandri/w/includes/OutputPage.php(983): OutputPage->setHTMLTitle()
#15 /var/www/liandri/w/includes/OutputPage.php(2477): OutputPage->setPageTitle()
#16 /var/www/liandri/w/includes/exception/MWExceptionRenderer.php(172): OutputPage->prepareErrorPage()
#17 /var/www/liandri/w/includes/exception/MWExceptionRenderer.php(55): MWExceptionRenderer::reportHTML()
#18 /var/www/liandri/w/includes/exception/MWExceptionHandler.php(75): MWExceptionRenderer::output()
#19 /var/www/liandri/w/includes/exception/MWExceptionHandler.php(130): MWExceptionHandler::report()
#20 [internal function]: MWExceptionHandler::handleException()
#21 {main}