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 page_id,page_len,page_is_redirect,page_latest FROM `page` WHERE page_namespace = '0' AND page_title = 'Log_in' LIMIT 1
Function: LinkCache::addLinkObj
Error: 1047 WSREP has not yet prepared node for application use (192.168.42.42:3307)
' in /var/www/ISWiki/testing/releases/20200221115006/lib/includes/db/Database.php:918
Stack trace:
#0 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/db/Database.php(885): DatabaseBase->reportQueryError('WSREP has not y...', 1047, 'SELECT page_id...', 'LinkCache::addL...', false)
#1 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/db/Database.php(1358): DatabaseBase->query('SELECT page_id...', 'LinkCache::addL...')
#2 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/db/Database.php(1445): DatabaseBase->select('page', Array, Array, 'LinkCache::addL...', Array, Array)
#3 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/cache/LinkCache.php(194): DatabaseBase->selectRow('page', Array, Array, 'LinkCache::addL...', Array)
#4 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/Title.php(2789): LinkCache->addLinkObj(Object(Title))
#5 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/Title.php(4120): Title->getArticleID()
#6 /var/www/ISWiki/testing/releases/20200221115006/lib/extensions/ISWiki/ISNiceDiscussions/NiceDiscussions.hooks.php(763): Title->exists()
#7 /var/www/ISWiki/testing/releases/20200221115006/lib/extensions/ISWiki/ISNiceDiscussions/NiceDiscussions.hooks.php(418): NiceDiscussions::checkActionAndNamespace(Object(Title), false)
#8 [internal function]: NiceDiscussions::beforePageDisplay(Object(OutputPage), Object(SkinIswiki))
#9 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/Hooks.php(216): call_user_func_array('NiceDiscussions...', Array)
#10 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/GlobalFunctions.php(3859): Hooks::run('BeforePageDispl...', Array)
#11 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/OutputPage.php(1979): wfRunHooks('BeforePageDispl...', Array)
#12 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/Wiki.php(406): OutputPage->output()
#13 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/Wiki.php(594): MediaWiki->finalCleanup()
#14 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/Wiki.php(503): MediaWiki->main()
#15 /var/www/ISWiki/testing/releases/20200221115006/lib/index.php(58): MediaWiki->run()
#16 {main}

Exception caught inside exception handler: exception 'DBUnexpectedError' with message 'Error in fetchRow(): WSREP has not yet prepared node for application use (192.168.42.42:3307)' in /var/www/ISWiki/testing/releases/20200221115006/lib/includes/db/DatabaseMysql.php:216
Stack trace:
#0 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/interwiki/Interwiki.php(168): DatabaseMysql->fetchRow(false)
#1 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/interwiki/Interwiki.php(60): Interwiki::load('energypedia_com...')
#2 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/interwiki/Interwiki.php(37): Interwiki::fetch('Energypedia_Com...')
#3 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/Title.php(2973): Interwiki::isValidInterwiki('Energypedia_Com...')
#4 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/Title.php(149): Title->secureAndSplit()
#5 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/Skin.php(1285): Title::newFromText('Energypedia Com...')
#6 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/Skin.php(1215): Skin->addToSidebarPlain(Array, '*Main Page?**Ma...')
#7 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/Skin.php(1195): Skin->addToSidebar(Array, 'sidebar')
#8 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/SkinTemplate.php(460): Skin->buildSidebar()
#9 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/OutputPage.php(1982): SkinTemplate->outputPage()
#10 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/Exception.php(182): OutputPage->output()
#11 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/Exception.php(209): MWException->reportHTML()
#12 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/Exception.php(490): MWException->report()
#13 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/Exception.php(569): MWExceptionHandler::report(Object(DBQueryError))
#14 /var/www/ISWiki/testing/releases/20200221115006/lib/includes/Wiki.php(506): MWExceptionHandler::handle(Object(DBQueryError))
#15 /var/www/ISWiki/testing/releases/20200221115006/lib/index.php(58): MediaWiki->run()
#16 {main}