MediaWiki internal error.

Original exception: [350bb477f6c267bda50b2ac8] /index.php?title=File:CONVECTION_OVEN_TEN_TRAY_GAS_4_page-0001.jpg&action=history Wikimedia\Rdbms\DBUnexpectedError: DB connection was already closed
Backtrace:
from /var/www/kbmechtrace/includes/libs/rdbms/database/Database.php(643)
#0 /var/www/kbmechtrace/includes/libs/rdbms/database/Database.php(929): Wikimedia\Rdbms\Database->assertHasConnectionHandle()
#1 /var/www/kbmechtrace/includes/libs/rdbms/database/Database.php(846): Wikimedia\Rdbms\Database->executeQuery()
#2 /var/www/kbmechtrace/includes/libs/rdbms/database/Database.php(1629): Wikimedia\Rdbms\Database->query()
#3 /var/www/kbmechtrace/includes/libs/rdbms/database/Database.php(1605): Wikimedia\Rdbms\Database->select()
#4 /var/www/kbmechtrace/includes/libs/rdbms/database/DBConnRef.php(119): Wikimedia\Rdbms\Database->selectFieldValues()
#5 /var/www/kbmechtrace/includes/libs/rdbms/database/DBConnRef.php(337): Wikimedia\Rdbms\DBConnRef->__call()
#6 /var/www/kbmechtrace/includes/libs/rdbms/querybuilder/SelectQueryBuilder.php(686): Wikimedia\Rdbms\DBConnRef->selectFieldValues()
#7 /var/www/kbmechtrace/includes/changetags/ChangeTags.php(1687): Wikimedia\Rdbms\SelectQueryBuilder->fetchFieldValues()
#8 /var/www/kbmechtrace/includes/libs/objectcache/wancache/WANObjectCache.php(1759): ChangeTags::{closure}()
#9 /var/www/kbmechtrace/includes/libs/objectcache/wancache/WANObjectCache.php(1589): WANObjectCache->fetchOrRegenerate()
#10 /var/www/kbmechtrace/includes/changetags/ChangeTags.php(1694): WANObjectCache->getWithSetCallback()
#11 /var/www/kbmechtrace/includes/changetags/ChangeTags.php(1658): ChangeTags::listExplicitlyDefinedTags()
#12 /var/www/kbmechtrace/includes/changetags/ChangeTags.php(1076): ChangeTags::listDefinedTags()
#13 /var/www/kbmechtrace/includes/htmlform/fields/HTMLTagFilter.php(30): ChangeTags::buildTagFilterSelector()
#14 /var/www/kbmechtrace/includes/htmlform/HTMLForm.php(1963): HTMLTagFilter->getOOUI()
#15 /var/www/kbmechtrace/includes/htmlform/HTMLForm.php(1534): HTMLForm->displaySection()
#16 /var/www/kbmechtrace/includes/htmlform/OOUIHTMLForm.php(286): HTMLForm->getBody()
#17 /var/www/kbmechtrace/includes/htmlform/HTMLForm.php(1316): OOUIHTMLForm->getBody()
#18 /var/www/kbmechtrace/includes/actions/HistoryAction.php(290): HTMLForm->getHTML()
#19 /var/www/kbmechtrace/includes/actions/FormlessAction.php(48): HistoryAction->onView()
#20 /var/www/kbmechtrace/includes/MediaWiki.php(556): FormlessAction->show()
#21 /var/www/kbmechtrace/includes/MediaWiki.php(333): MediaWiki->performAction()
#22 /var/www/kbmechtrace/includes/MediaWiki.php(923): MediaWiki->performRequest()
#23 /var/www/kbmechtrace/includes/MediaWiki.php(576): MediaWiki->main()
#24 /var/www/kbmechtrace/index.php(50): MediaWiki->run()
#25 /var/www/kbmechtrace/index.php(46): wfIndexMain()
#26 {main}

Exception caught inside exception handler: [350bb477f6c267bda50b2ac8] /index.php?title=File:CONVECTION_OVEN_TEN_TRAY_GAS_4_page-0001.jpg&action=history Wikimedia\Rdbms\DBConnectionError: Cannot access the database: No such file or directory (localhost)
Backtrace:
from /var/www/kbmechtrace/includes/libs/rdbms/loadbalancer/LoadBalancer.php(1247)
#0 /var/www/kbmechtrace/includes/libs/rdbms/loadbalancer/LoadBalancer.php(894): Wikimedia\Rdbms\LoadBalancer->reportConnectionError()
#1 /var/www/kbmechtrace/includes/libs/rdbms/loadbalancer/LoadBalancer.php(861): Wikimedia\Rdbms\LoadBalancer->getServerConnection()
#2 /var/www/kbmechtrace/includes/libs/rdbms/database/DBConnRef.php(103): Wikimedia\Rdbms\LoadBalancer->getConnectionInternal()
#3 /var/www/kbmechtrace/includes/libs/rdbms/database/DBConnRef.php(117): Wikimedia\Rdbms\DBConnRef->ensureConnection()
#4 /var/www/kbmechtrace/includes/libs/rdbms/database/DBConnRef.php(722): Wikimedia\Rdbms\DBConnRef->__call()
#5 /var/www/kbmechtrace/includes/libs/rdbms/database/Database.php(2964): Wikimedia\Rdbms\DBConnRef->getSessionLagStatus()
#6 /var/www/kbmechtrace/includes/cache/LinkCache.php(460): Wikimedia\Rdbms\Database::getCacheSetOptions()
#7 /var/www/kbmechtrace/includes/libs/objectcache/wancache/WANObjectCache.php(1759): LinkCache->{closure}()
#8 /var/www/kbmechtrace/includes/libs/objectcache/wancache/WANObjectCache.php(1589): WANObjectCache->fetchOrRegenerate()
#9 /var/www/kbmechtrace/includes/cache/LinkCache.php(467): WANObjectCache->getWithSetCallback()
#10 /var/www/kbmechtrace/includes/cache/LinkCache.php(507): LinkCache->getGoodLinkRowInternal()
#11 /var/www/kbmechtrace/includes/page/PageStore.php(188): LinkCache->getGoodLinkRow()
#12 /var/www/kbmechtrace/includes/page/PageStore.php(154): MediaWiki\Page\PageStore->getPageByNameViaLinkCache()
#13 /var/www/kbmechtrace/includes/page/PageStore.php(326): MediaWiki\Page\PageStore->getPageByName()
#14 /var/www/kbmechtrace/includes/title/Title.php(4166): MediaWiki\Page\PageStore->getPageByReference()
#15 /var/www/kbmechtrace/includes/title/Title.php(2876): MediaWiki\Title\Title->getFieldFromPageStore()
#16 /var/www/kbmechtrace/includes/title/Title.php(3522): MediaWiki\Title\Title->getArticleID()
#17 /var/www/kbmechtrace/extensions/PWA/PWA.php(129): MediaWiki\Title\Title->exists()
#18 /var/www/kbmechtrace/includes/HookContainer/HookContainer.php(338): MediaWiki\Extension\PWA\PWA::onBeforePageDisplay()
#19 /var/www/kbmechtrace/includes/HookContainer/HookContainer.php(137): MediaWiki\HookContainer\HookContainer->callLegacyHook()
#20 /var/www/kbmechtrace/includes/HookContainer/HookRunner.php(942): MediaWiki\HookContainer\HookContainer->run()
#21 /var/www/kbmechtrace/includes/OutputPage.php(2894): MediaWiki\HookContainer\HookRunner->onBeforePageDisplay()
#22 /var/www/kbmechtrace/includes/exception/MWExceptionRenderer.php(184): OutputPage->output()
#23 /var/www/kbmechtrace/includes/exception/MWExceptionRenderer.php(103): MWExceptionRenderer::reportHTML()
#24 /var/www/kbmechtrace/includes/exception/MWExceptionHandler.php(132): MWExceptionRenderer::output()
#25 /var/www/kbmechtrace/includes/exception/MWExceptionHandler.php(249): MWExceptionHandler::report()
#26 /var/www/kbmechtrace/includes/MediaWiki.php(595): MWExceptionHandler::handleException()
#27 /var/www/kbmechtrace/index.php(50): MediaWiki->run()
#28 /var/www/kbmechtrace/index.php(46): wfIndexMain()
#29 {main}