MediaWiki internal error.

Original exception: exception 'DBQueryError' with message 'A database error has occurred. Did you forget to run maintenance/update.php after upgrading? See: https://www.mediawiki.org/wiki/Manual:Upgrading#Run_the_update_script
Query: SELECT vt_tag FROM `valid_tag`
Function: ChangeTags::listDefinedTags
Error: 1927 Lost connection to backend server: connection closed by peer (server3: Generated event) (database_maxscale:4006)
' in /var/www/ISWiki/prod/current/lib/includes/db/Database.php:918
Stack trace:
#0 /var/www/ISWiki/prod/current/lib/includes/db/Database.php(885): DatabaseBase->reportQueryError('Lost connection...', 1927, 'SELECT vt_tag ...', 'ChangeTags::lis...', false)
#1 /var/www/ISWiki/prod/current/lib/includes/db/Database.php(1358): DatabaseBase->query('SELECT vt_tag ...', 'ChangeTags::lis...')
#2 /var/www/ISWiki/prod/current/lib/includes/ChangeTags.php(249): DatabaseBase->select('valid_tag', 'vt_tag', Array, 'ChangeTags::lis...')
#3 /var/www/ISWiki/prod/current/lib/includes/ChangeTags.php(209): ChangeTags::listDefinedTags()
#4 /var/www/ISWiki/prod/current/lib/includes/specials/SpecialRecentchangeslinked.php(231): ChangeTags::buildTagFilterSelector('')
#5 /var/www/ISWiki/prod/current/lib/includes/specials/SpecialRecentchanges.php(564): SpecialRecentchangeslinked->getExtraOptions(Object(FormOptions))
#6 /var/www/ISWiki/prod/current/lib/includes/specials/SpecialRecentchanges.php(161): SpecialRecentChanges->doHeader(Object(FormOptions))
#7 /var/www/ISWiki/prod/current/lib/includes/SpecialPageFactory.php(476): SpecialRecentChanges->execute(NULL)
#8 /var/www/ISWiki/prod/current/lib/includes/Wiki.php(263): SpecialPageFactory::executePath(Object(Title), Object(RequestContext))
#9 /var/www/ISWiki/prod/current/lib/includes/Wiki.php(593): MediaWiki->performRequest()
#10 /var/www/ISWiki/prod/current/lib/includes/Wiki.php(503): MediaWiki->main()
#11 /var/www/ISWiki/prod/current/lib/index.php(58): MediaWiki->run()
#12 {main}

Exception caught inside exception handler: exception 'DBQueryError' with message 'A database error has occurred. Did you forget to run maintenance/update.php after upgrading? See: https://www.mediawiki.org/wiki/Manual:Upgrading#Run_the_update_script
Query: SELECT value,exptime FROM `objectcache` WHERE keyname = 'webmol_openmodwiki:resourceloader:filter:minify-css:7:c88e2bcd56513749bec09a7e29cb3ffa' LIMIT 1
Function: SqlBagOStuff::get
Error: 1927 Lost connection to backend server: connection closed by peer (server3: Generated event) (database_maxscale:4006)
' in /var/www/ISWiki/prod/current/lib/includes/db/Database.php:918
Stack trace:
#0 /var/www/ISWiki/prod/current/lib/includes/db/Database.php(885): DatabaseBase->reportQueryError('Lost connection...', 1927, 'SELECT value,e...', 'SqlBagOStuff::g...', false)
#1 /var/www/ISWiki/prod/current/lib/includes/db/Database.php(1358): DatabaseBase->query('SELECT value,e...', 'SqlBagOStuff::g...')
#2 /var/www/ISWiki/prod/current/lib/includes/db/Database.php(1445): DatabaseBase->select('objectcache', Array, Array, 'SqlBagOStuff::g...', Array, Array)
#3 /var/www/ISWiki/prod/current/lib/includes/objectcache/SqlBagOStuff.php(124): DatabaseBase->selectRow('objectcache', Array, Array, 'SqlBagOStuff::g...')
#4 /var/www/ISWiki/prod/current/lib/includes/resourceloader/ResourceLoader.php(149): SqlBagOStuff->get('webmol_openmodw...')
#5 /var/www/ISWiki/prod/current/lib/includes/resourceloader/ResourceLoader.php(783): ResourceLoader->filter('minify-css', 'a:lang(ar), a:l...')
#6 /var/www/ISWiki/prod/current/lib/includes/OutputPage.php(2594): ResourceLoader->makeModuleResponse(Object(ResourceLoaderContext), Array)
#7 /var/www/ISWiki/prod/current/lib/includes/OutputPage.php(3310): OutputPage->makeResourceLoaderLink(Array, 'styles')
#8 /var/www/ISWiki/prod/current/lib/includes/OutputPage.php(2407): OutputPage->buildCssLinks()
#9 /var/www/ISWiki/prod/current/lib/includes/SkinTemplate.php(465): OutputPage->headElement(Object(SkinIswiki))
#10 /var/www/ISWiki/prod/current/lib/includes/OutputPage.php(1982): SkinTemplate->outputPage()
#11 /var/www/ISWiki/prod/current/lib/includes/Exception.php(182): OutputPage->output()
#12 /var/www/ISWiki/prod/current/lib/includes/Exception.php(209): MWException->reportHTML()
#13 /var/www/ISWiki/prod/current/lib/includes/Exception.php(490): MWException->report()
#14 /var/www/ISWiki/prod/current/lib/includes/Exception.php(569): MWExceptionHandler::report(Object(DBQueryError))
#15 /var/www/ISWiki/prod/current/lib/includes/Wiki.php(506): MWExceptionHandler::handle(Object(DBQueryError))
#16 /var/www/ISWiki/prod/current/lib/index.php(58): MediaWiki->run()
#17 {main}