MediaWiki internal error.

Original exception: [ZfjydFlPzY6B4agw0hFKHQAAAFI] /wiki/%D0%9D%D0%B5%D0%BF%D0%BE%D0%BD%D1%8F%D1%82%D0%BD%D0%BE%D0%B3%D0%BE_%D0%BF%D0%BE%D0%BB%D0%B0 Wikimedia\Rdbms\DBConnectionError from line 1423 of /var/www/html/w/includes/libs/rdbms/loadbalancer/LoadBalancer.php: Cannot access the database: Unknown error (localhost)
Backtrace:
#0 /var/www/html/w/includes/libs/rdbms/loadbalancer/LoadBalancer.php(937): Wikimedia\Rdbms\LoadBalancer->reportConnectionError()
#1 /var/www/html/w/includes/libs/rdbms/loadbalancer/LoadBalancer.php(904): Wikimedia\Rdbms\LoadBalancer->getServerConnection(integer, string, integer)
#2 /var/www/html/w/includes/libs/rdbms/loadbalancer/LoadBalancer.php(1049): Wikimedia\Rdbms\LoadBalancer->getConnection(integer, array, string, integer)
#3 /var/www/html/w/includes/GlobalFunctions.php(2463): Wikimedia\Rdbms\LoadBalancer->getMaintenanceConnectionRef(integer, array, string)
#4 /var/www/html/w/includes/cache/localisation/LCStoreDB.php(56): wfGetDB(integer)
#5 /var/www/html/w/includes/cache/localisation/LocalisationCache.php(449): LCStoreDB->get(string, string)
#6 /var/www/html/w/includes/cache/localisation/LocalisationCache.php(495): LocalisationCache->isExpired(string)
#7 /var/www/html/w/includes/cache/localisation/LocalisationCache.php(371): LocalisationCache->initLanguage(string)
#8 /var/www/html/w/includes/cache/localisation/LocalisationCache.php(312): LocalisationCache->loadItem(string, string)
#9 /var/www/html/w/includes/language/LanguageFallback.php(106): LocalisationCache->getItem(string, string)
#10 /var/www/html/w/includes/language/LanguageFactory.php(175): MediaWiki\Languages\LanguageFallback->getAll(string)
#11 /var/www/html/w/includes/language/LanguageFactory.php(121): MediaWiki\Languages\LanguageFactory->newFromCode(string)
#12 /var/www/html/w/includes/ServiceWiring.php(241): MediaWiki\Languages\LanguageFactory->getLanguage(string)
#13 /var/www/html/w/vendor/wikimedia/services/src/ServiceContainer.php(447): Wikimedia\Services\ServiceContainer->{closure}(MediaWiki\MediaWikiServices)
#14 /var/www/html/w/vendor/wikimedia/services/src/ServiceContainer.php(416): Wikimedia\Services\ServiceContainer->createService(string)
#15 /var/www/html/w/includes/MediaWikiServices.php(623): Wikimedia\Services\ServiceContainer->getService(string)
#16 /var/www/html/w/includes/Setup.php(700): MediaWiki\MediaWikiServices->getContentLanguage()
#17 /var/www/html/w/includes/WebStart.php(89): require_once(string)
#18 /var/www/html/w/index.php(44): require(string)
#19 {main}

Exception caught inside exception handler: [ZfjydFlPzY6B4agw0hFKHQAAAFI] /wiki/%D0%9D%D0%B5%D0%BF%D0%BE%D0%BD%D1%8F%D1%82%D0%BD%D0%BE%D0%B3%D0%BE_%D0%BF%D0%BE%D0%BB%D0%B0 Wikimedia\Rdbms\DBConnectionError from line 1423 of /var/www/html/w/includes/libs/rdbms/loadbalancer/LoadBalancer.php: Cannot access the database: Unknown error (localhost)
Backtrace:
#0 /var/www/html/w/includes/libs/rdbms/loadbalancer/LoadBalancer.php(937): Wikimedia\Rdbms\LoadBalancer->reportConnectionError()
#1 /var/www/html/w/includes/libs/rdbms/loadbalancer/LoadBalancer.php(904): Wikimedia\Rdbms\LoadBalancer->getServerConnection(integer, string, integer)
#2 /var/www/html/w/includes/libs/rdbms/loadbalancer/LoadBalancer.php(1049): Wikimedia\Rdbms\LoadBalancer->getConnection(integer, array, string, integer)
#3 /var/www/html/w/includes/GlobalFunctions.php(2463): Wikimedia\Rdbms\LoadBalancer->getMaintenanceConnectionRef(integer, array, string)
#4 /var/www/html/w/includes/cache/localisation/LCStoreDB.php(56): wfGetDB(integer)
#5 /var/www/html/w/includes/cache/localisation/LocalisationCache.php(394): LCStoreDB->get(string, string)
#6 /var/www/html/w/includes/cache/localisation/LocalisationCache.php(312): LocalisationCache->loadItem(string, string)
#7 /var/www/html/w/includes/language/LanguageFallback.php(106): LocalisationCache->getItem(string, string)
#8 /var/www/html/w/includes/language/LanguageFactory.php(175): MediaWiki\Languages\LanguageFallback->getAll(string)
#9 /var/www/html/w/includes/language/LanguageFactory.php(121): MediaWiki\Languages\LanguageFactory->newFromCode(string)
#10 /var/www/html/w/includes/ServiceWiring.php(241): MediaWiki\Languages\LanguageFactory->getLanguage(string)
#11 /var/www/html/w/vendor/wikimedia/services/src/ServiceContainer.php(447): Wikimedia\Services\ServiceContainer->{closure}(MediaWiki\MediaWikiServices)
#12 /var/www/html/w/vendor/wikimedia/services/src/ServiceContainer.php(416): Wikimedia\Services\ServiceContainer->createService(string)
#13 /var/www/html/w/includes/MediaWikiServices.php(623): Wikimedia\Services\ServiceContainer->getService(string)
#14 /var/www/html/w/includes/ServiceWiring.php(694): MediaWiki\MediaWikiServices->getContentLanguage()
#15 /var/www/html/w/vendor/wikimedia/services/src/ServiceContainer.php(447): Wikimedia\Services\ServiceContainer->{closure}(MediaWiki\MediaWikiServices)
#16 /var/www/html/w/vendor/wikimedia/services/src/ServiceContainer.php(416): Wikimedia\Services\ServiceContainer->createService(string)
#17 /var/www/html/w/includes/MediaWikiServices.php(925): Wikimedia\Services\ServiceContainer->getService(string)
#18 /var/www/html/w/includes/exception/MWExceptionRenderer.php(329): MediaWiki\MediaWikiServices->getMessageCache()
#19 /var/www/html/w/includes/exception/MWExceptionRenderer.php(63): MWExceptionRenderer::reportOutageHTML(Wikimedia\Rdbms\DBConnectionError)
#20 /var/www/html/w/includes/exception/MWExceptionHandler.php(106): MWExceptionRenderer::output(Wikimedia\Rdbms\DBConnectionError, integer)
#21 /var/www/html/w/includes/exception/MWExceptionHandler.php(185): MWExceptionHandler::report(Wikimedia\Rdbms\DBConnectionError)
#22 /var/www/html/w/includes/exception/MWExceptionHandler.php(156): MWExceptionHandler::handleException(Wikimedia\Rdbms\DBConnectionError, string)
#23 [internal function]: MWExceptionHandler::handleUncaughtException(Wikimedia\Rdbms\DBConnectionError)
#24 {main}