MediaWiki internal error.

Original exception: [7c17ffcdaec1ebad2fa712c6] /index.php?title=Main_Page&diff=6017&oldid=4385 Wikimedia\Rdbms\DBConnectionError from line 1195 of /var/www/G6_wiki/includes/libs/rdbms/loadbalancer/LoadBalancer.php: Cannot access the database: Unknown error (localhost)
Backtrace:
#0 /var/www/G6_wiki/includes/libs/rdbms/loadbalancer/LoadBalancer.php(769): Wikimedia\Rdbms\LoadBalancer->reportConnectionError()
#1 /var/www/G6_wiki/includes/GlobalFunctions.php(2694): Wikimedia\Rdbms\LoadBalancer->getConnection(integer, array, boolean)
#2 /var/www/G6_wiki/includes/cache/localisation/LCStoreDB.php(54): wfGetDB(integer)
#3 /var/www/G6_wiki/includes/cache/localisation/LocalisationCache.php(410): LCStoreDB->get(string, string)
#4 /var/www/G6_wiki/includes/cache/localisation/LocalisationCache.php(456): LocalisationCache->isExpired(string)
#5 /var/www/G6_wiki/includes/cache/localisation/LocalisationCache.php(332): LocalisationCache->initLanguage(string)
#6 /var/www/G6_wiki/includes/cache/localisation/LocalisationCache.php(273): LocalisationCache->loadItem(string, string)
#7 /var/www/G6_wiki/languages/Language.php(4613): LocalisationCache->getItem(string, string)
#8 /var/www/G6_wiki/languages/Language.php(261): Language::getFallbacksFor(string)
#9 /var/www/G6_wiki/languages/Language.php(222): Language::newFromCode(string)
#10 /var/www/G6_wiki/includes/ServiceWiring.php(110): Language::factory(string)
#11 /var/www/G6_wiki/includes/services/ServiceContainer.php(430): MediaWiki\Services\ServiceContainer->{closure}(MediaWiki\MediaWikiServices)
#12 /var/www/G6_wiki/includes/services/ServiceContainer.php(414): MediaWiki\Services\ServiceContainer->createService(string)
#13 /var/www/G6_wiki/includes/MediaWikiServices.php(496): MediaWiki\Services\ServiceContainer->getService(string)
#14 /var/www/G6_wiki/includes/Setup.php(809): MediaWiki\MediaWikiServices->getContentLanguage()
#15 /var/www/G6_wiki/includes/WebStart.php(77): require_once(string)
#16 /var/www/G6_wiki/index.php(39): require(string)
#17 {main}

Exception caught inside exception handler: [7c17ffcdaec1ebad2fa712c6] /index.php?title=Main_Page&diff=6017&oldid=4385 Wikimedia\Rdbms\DBConnectionError from line 1195 of /var/www/G6_wiki/includes/libs/rdbms/loadbalancer/LoadBalancer.php: Cannot access the database: Unknown error (localhost)
Backtrace:
#0 /var/www/G6_wiki/includes/libs/rdbms/loadbalancer/LoadBalancer.php(769): Wikimedia\Rdbms\LoadBalancer->reportConnectionError()
#1 /var/www/G6_wiki/includes/GlobalFunctions.php(2694): Wikimedia\Rdbms\LoadBalancer->getConnection(integer, array, boolean)
#2 /var/www/G6_wiki/includes/cache/localisation/LCStoreDB.php(54): wfGetDB(integer)
#3 /var/www/G6_wiki/includes/cache/localisation/LocalisationCache.php(355): LCStoreDB->get(string, string)
#4 /var/www/G6_wiki/includes/cache/localisation/LocalisationCache.php(273): LocalisationCache->loadItem(string, string)
#5 /var/www/G6_wiki/languages/Language.php(4613): LocalisationCache->getItem(string, string)
#6 /var/www/G6_wiki/languages/Language.php(261): Language::getFallbacksFor(string)
#7 /var/www/G6_wiki/languages/Language.php(222): Language::newFromCode(string)
#8 /var/www/G6_wiki/includes/ServiceWiring.php(110): Language::factory(string)
#9 /var/www/G6_wiki/includes/services/ServiceContainer.php(430): MediaWiki\Services\ServiceContainer->{closure}(MediaWiki\MediaWikiServices)
#10 /var/www/G6_wiki/includes/services/ServiceContainer.php(414): MediaWiki\Services\ServiceContainer->createService(string)
#11 /var/www/G6_wiki/includes/MediaWikiServices.php(496): MediaWiki\Services\ServiceContainer->getService(string)
#12 /var/www/G6_wiki/includes/cache/MessageCache.php(126): MediaWiki\MediaWikiServices->getContentLanguage()
#13 /var/www/G6_wiki/includes/exception/MWExceptionRenderer.php(312): MessageCache::singleton()
#14 /var/www/G6_wiki/includes/exception/MWExceptionRenderer.php(51): MWExceptionRenderer::reportOutageHTML(Wikimedia\Rdbms\DBConnectionError)
#15 /var/www/G6_wiki/includes/exception/MWExceptionHandler.php(98): MWExceptionRenderer::output(Wikimedia\Rdbms\DBConnectionError, integer)
#16 /var/www/G6_wiki/includes/exception/MWExceptionHandler.php(172): MWExceptionHandler::report(Wikimedia\Rdbms\DBConnectionError)
#17 /var/www/G6_wiki/includes/exception/MWExceptionHandler.php(144): MWExceptionHandler::handleException(Wikimedia\Rdbms\DBConnectionError)
#18 [internal function]: MWExceptionHandler::handleUncaughtException(Wikimedia\Rdbms\DBConnectionError)
#19 {main}