MediaWiki version: 1.35.0-wmf.37
PHP Warning: Invalid argument supplied for foreach()
Doesn't seem to happen deterministically for this url at any rate
#0 /srv/mediawiki/php-1.35.0-wmf.37/includes/libs/rdbms/loadbalancer/LoadBalancer.php(2149): MWExceptionHandler::handleError(integer, string, string, integer, array)
#1 /srv/mediawiki/php-1.35.0-wmf.37/includes/libs/rdbms/loadbalancer/LoadBalancer.php(1835): Wikimedia\Rdbms\LoadBalancer->forEachOpenMasterConnection(Closure)
#2 /srv/mediawiki/php-1.35.0-wmf.37/includes/libs/rdbms/lbfactory/LBFactory.php(349): Wikimedia\Rdbms\LoadBalancer->runMasterTransactionListenerCallbacks(string, integer)
#3 /srv/mediawiki/php-1.35.0-wmf.37/includes/libs/rdbms/lbfactory/LBFactoryMulti.php(222): Wikimedia\Rdbms\LBFactory->Wikimedia\Rdbms\{closure}(Wikimedia\Rdbms\LoadBalancer)
#4 /srv/mediawiki/php-1.35.0-wmf.37/includes/libs/rdbms/lbfactory/LBFactory.php(351): Wikimedia\Rdbms\LBFactoryMulti->forEachLB(Closure)
#5 /srv/mediawiki/php-1.35.0-wmf.37/includes/libs/rdbms/lbfactory/LBFactory.php(312): Wikimedia\Rdbms\LBFactory->executePostTransactionCallbacks()
#6 /srv/mediawiki/php-1.35.0-wmf.37/includes/libs/rdbms/lbfactory/LBFactory.php(232): Wikimedia\Rdbms\LBFactory->commitMasterChanges(string)
#7 /srv/mediawiki/php-1.35.0-wmf.37/includes/MediaWiki.php(1079): Wikimedia\Rdbms\LBFactory->shutdown(integer)
#8 /srv/mediawiki/php-1.35.0-wmf.37/includes/MediaWiki.php(849): MediaWiki->restInPeace()
#9 /srv/mediawiki/php-1.35.0-wmf.37/includes/MediaWiki.php(861): MediaWiki->{closure}()
#10 /srv/mediawiki/php-1.35.0-wmf.37/api.php(119): MediaWiki->doPostOutputShutdown()
#11 /srv/mediawiki/w/api.php(3): require(string)
#12 {main}public function forEachOpenMasterConnection( $callback, array $params = [] ) { $masterIndex = $this->getWriterIndex(); foreach ( $this->conns as $connsByServer ) { … }
conns is declared without value, and assigned from two places. Presumably it is called too early by something before it is possible/allowed to have a connection yet. Unclear whether that is a bad caller or whether it needs to be supported. Depends on intent and required behaviour.
If investigation concludes that this condition is impossible, then this might be a case of T245183 / T253673, which I expect in part because it happened onced only and on one server only.