MediaWiki internal error.

Original exception: [a7f26de8ed6e877cb0800a81] /index.php?title=Special:UserLogin&returnto=%C4%80dolfs+Hitlers&returntoquery=printable%3Dyes Wikimedia\Rdbms\DBQueryError from line 1496 of /var/lib/mediawiki/includes/libs/rdbms/database/Database.php: A connection error occurred.
Query: SELECT page_title,page_latest FROM `wik2page` WHERE page_is_redirect = '0' AND page_namespace = '8' AND (page_title LIKE '%/en' ESCAPE '`' ) AND (page_len > 10000)
Function: MessageCache::loadFromDB(en)-big
Error: 2006 MySQL server has gone away (localhost)

Backtrace:
#0 /var/lib/mediawiki/includes/libs/rdbms/database/Database.php(1466): Wikimedia\Rdbms\Database->makeQueryException(string, integer, string, string)
#1 /var/lib/mediawiki/includes/libs/rdbms/database/Database.php(1226): Wikimedia\Rdbms\Database->reportQueryError(string, integer, string, string, boolean)
#2 /var/lib/mediawiki/includes/libs/rdbms/database/Database.php(1693): Wikimedia\Rdbms\Database->query(string, string)
#3 /var/lib/mediawiki/includes/cache/MessageCache.php(511): Wikimedia\Rdbms\Database->select(string, array, array, string)
#4 /var/lib/mediawiki/includes/cache/MessageCache.php(427): MessageCache->loadFromDB(string, NULL)
#5 /var/lib/mediawiki/includes/cache/MessageCache.php(350): MessageCache->loadFromDBWithLock(string, array, NULL)
#6 /var/lib/mediawiki/includes/cache/MessageCache.php(1031): MessageCache->load(string)
#7 /var/lib/mediawiki/includes/cache/MessageCache.php(985): MessageCache->getMsgFromNamespace(string, string)
#8 /var/lib/mediawiki/includes/cache/MessageCache.php(928): MessageCache->getMessageForLang(Language, string, boolean, array)
#9 /var/lib/mediawiki/includes/cache/MessageCache.php(870): MessageCache->getMessageFromFallbackChain(Language, string, boolean)
#10 /var/lib/mediawiki/includes/Message.php(1299): MessageCache->get(string, boolean, Language)
#11 /var/lib/mediawiki/includes/Message.php(991): Message->fetchMessage()
#12 /var/lib/mediawiki/includes/skins/Skin.php(1377): Message->exists()
#13 /var/lib/mediawiki/includes/skins/Skin.php(1334): Skin->addToSidebarPlain(array, string)
#14 /var/lib/mediawiki/includes/skins/Skin.php(1290): Skin->addToSidebar(array, string)
#15 /var/lib/mediawiki/includes/skins/Skin.php(1316): Skin->{closure}()
#16 /var/lib/mediawiki/includes/skins/SkinTemplate.php(465): Skin->buildSidebar()
#17 /var/lib/mediawiki/includes/skins/SkinTemplate.php(225): SkinTemplate->prepareQuickTemplate()
#18 /var/lib/mediawiki/includes/OutputPage.php(2706): SkinTemplate->outputPage()
#19 /var/lib/mediawiki/includes/MediaWiki.php(867): OutputPage->output(boolean)
#20 /var/lib/mediawiki/includes/MediaWiki.php(879): MediaWiki->{closure}()
#21 /var/lib/mediawiki/includes/MediaWiki.php(517): MediaWiki->main()
#22 /var/lib/mediawiki/index.php(46): MediaWiki->run()
#23 {main}

Exception caught inside exception handler: [a7f26de8ed6e877cb0800a81] /index.php?title=Special:UserLogin&returnto=%C4%80dolfs+Hitlers&returntoquery=printable%3Dyes Wikimedia\Rdbms\DBConnectionError from line 1195 of /var/lib/mediawiki/includes/libs/rdbms/loadbalancer/LoadBalancer.php: Cannot access the database: Unknown error (localhost)
Backtrace:
#0 /var/lib/mediawiki/includes/libs/rdbms/loadbalancer/LoadBalancer.php(769): Wikimedia\Rdbms\LoadBalancer->reportConnectionError()
#1 /var/lib/mediawiki/includes/GlobalFunctions.php(2694): Wikimedia\Rdbms\LoadBalancer->getConnection(integer, array, boolean)
#2 /var/lib/mediawiki/includes/cache/localisation/LCStoreDB.php(54): wfGetDB(integer)
#3 /var/lib/mediawiki/includes/cache/localisation/LocalisationCache.php(391): LCStoreDB->get(string, string)
#4 /var/lib/mediawiki/includes/cache/localisation/LocalisationCache.php(294): LocalisationCache->loadSubitem(string, string, string)
#5 /var/lib/mediawiki/languages/Language.php(2643): LocalisationCache->getSubitem(string, string, string)
#6 /var/lib/mediawiki/includes/cache/MessageCache.php(970): Language->getMessage(string)
#7 /var/lib/mediawiki/includes/cache/MessageCache.php(928): MessageCache->getMessageForLang(Language, string, boolean, array)
#8 /var/lib/mediawiki/includes/cache/MessageCache.php(870): MessageCache->getMessageFromFallbackChain(Language, string, boolean)
#9 /var/lib/mediawiki/includes/Message.php(1299): MessageCache->get(string, boolean, Language)
#10 /var/lib/mediawiki/includes/Message.php(851): Message->fetchMessage()
#11 /var/lib/mediawiki/includes/Message.php(943): Message->toString(string)
#12 /var/lib/mediawiki/includes/exception/MWExceptionRenderer.php(132): Message->text()
#13 /var/lib/mediawiki/includes/exception/MWExceptionRenderer.php(53): MWExceptionRenderer::reportHTML(Wikimedia\Rdbms\DBQueryError)
#14 /var/lib/mediawiki/includes/exception/MWExceptionHandler.php(98): MWExceptionRenderer::output(Wikimedia\Rdbms\DBQueryError, integer)
#15 /var/lib/mediawiki/includes/exception/MWExceptionHandler.php(172): MWExceptionHandler::report(Wikimedia\Rdbms\DBQueryError)
#16 /var/lib/mediawiki/includes/MediaWiki.php(544): MWExceptionHandler::handleException(Wikimedia\Rdbms\DBQueryError)
#17 /var/lib/mediawiki/index.php(46): MediaWiki->run()
#18 {main}