Seems to happen for every request of the form `/wiki/Special:SetSiteLink/Qnnnnnn`
```
Expectation (masterConns <= 0) by MediaWiki::main not met:
[connect to 10.64.16.144 (wikidatawiki)]
#0 /srv/mediawiki/php-1.29.0-wmf.6/includes/libs/rdbms/TransactionProfiler.php(160): TransactionProfiler->reportExpectationViolated()
#1 /srv/mediawiki/php-1.29.0-wmf.6/includes/libs/rdbms/loadbalancer/LoadBalancer.php(587): TransactionProfiler->recordConnection()
#2 /srv/mediawiki/php-1.29.0-wmf.6/includes/dao/DBAccessBase.php(61): LoadBalancer->getConnection()
#3 /srv/mediawiki/php-1.29.0-wmf.6/extensions/Wikidata/extensions/Wikibase/lib/includes/Store/Sql/WikiPageEntityMetaDataLookup.php(214): DBAccessBase->getConnection()
#4 /srv/mediawiki/php-1.29.0-wmf.6/extensions/Wikidata/extensions/Wikibase/lib/includes/Store/Sql/WikiPageEntityMetaDataLookup.php(98): Wikibase\Lib\Store\Sql\WikiPageEntityMetaDataLookup->selectRevisionInformationMultiple()
#5 /srv/mediawiki/php-1.29.0-wmf.6/extensions/Wikidata/extensions/Wikibase/lib/includes/Store/Sql/PrefetchingWikiPageEntityMetaDataAccessor.php(151): Wikibase\Lib\Store\Sql\WikiPageEntityMetaDataLookup->loadRevisionInformation()
#6 /srv/mediawiki/php-1.29.0-wmf.6/extensions/Wikidata/extensions/Wikibase/lib/includes/Store/Sql/WikiPageEntityRevisionLookup.php(84): Wikibase\Lib\Store\Sql\PrefetchingWikiPageEntityMetaDataAccessor->loadRevisionInformation()
#7 /srv/mediawiki/php-1.29.0-wmf.6/extensions/Wikidata/extensions/Wikibase/repo/includes/Specials/SpecialModifyEntity.php(197): Wikibase\Lib\Store\WikiPageEntityRevisionLookup->getEntityRevision()
#8 /srv/mediawiki/php-1.29.0-wmf.6/extensions/Wikidata/extensions/Wikibase/repo/includes/Specials/SpecialModifyEntity.php(180): Wikibase\Repo\Specials\SpecialModifyEntity->loadEntity()
#9 /srv/mediawiki/php-1.29.0-wmf.6/extensions/Wikidata/extensions/Wikibase/repo/includes/Specials/SpecialSetSiteLink.php(108): Wikibase\Repo\Specials\SpecialModifyEntity->prepareArguments()
#10 /srv/mediawiki/php-1.29.0-wmf.6/extensions/Wikidata/extensions/Wikibase/repo/includes/Specials/SpecialModifyEntity.php(129): Wikibase\Repo\Specials\SpecialSetSiteLink->prepareArguments()
#11 /srv/mediawiki/php-1.29.0-wmf.6/includes/specialpage/SpecialPage.php(522): Wikibase\Repo\Specials\SpecialModifyEntity->execute()
#12 /srv/mediawiki/php-1.29.0-wmf.6/includes/specialpage/SpecialPageFactory.php(577): SpecialPage->run()
#13 /srv/mediawiki/php-1.29.0-wmf.6/includes/MediaWiki.php(283): SpecialPageFactory::executePath()
#14 /srv/mediawiki/php-1.29.0-wmf.6/includes/MediaWiki.php(851): MediaWiki->performRequest()
#15 /srv/mediawiki/php-1.29.0-wmf.6/includes/MediaWiki.php(512): MediaWiki->main()
#16 /srv/mediawiki/php-1.29.0-wmf.6/index.php(43): MediaWiki->run()
#17 /srv/mediawiki/w/index.php(3): include()
#18 {main}
```