This exception has started to show little over a month ago (possibly earlier) in Logstash under mediawiki-errors.
Only for enwiki and only from codfw appservers and api_appservers (mw2177, mw2137, mw2144, ..). Most likely triggered by monitoring requests, but still these exceptions shouldn't happen.
Is it not possible to write to the active jobqueue from codfw? While it's fine not to support database writes (given we don't support active-active yet, so there aren't meant to be write requests there), as far as I know, we do have a small number of jobs that can be inserted from read-only requests - as indicated by these errors.
```counterexample
[W0lDugrAIEIAAL2owt0AAAAL] /wiki/Main_Page JobQueueReadOnlyError from line 693 of /srv/mediawiki/php-1.32.0-wmf.12/includes/jobqueue/JobQueue.php:
Job queue is read-only: MediaWiki is in read-only mode for maintenance. Please try again in a few minutes.
#0 /srv/mediawiki/php-1.32.0-wmf.12/includes/jobqueue/JobQueue.php(316): JobQueue->assertNotReadOnly()
#1 /srv/mediawiki/php-1.32.0-wmf.12/includes/jobqueue/JobQueue.php(302): JobQueue->batchPush(array, integer)
#2 /srv/mediawiki/php-1.32.0-wmf.12/includes/jobqueue/JobQueueGroup.php(154): JobQueue->push(array)
#3 /srv/mediawiki/php-1.32.0-wmf.12/includes/jobqueue/JobQueueGroup.php(218): JobQueueGroup->push(array)
#4 /srv/mediawiki/php-1.32.0-wmf.12/includes/deferred/MWCallableUpdate.php(34): JobQueueGroup::pushLazyJobs()
#5 /srv/mediawiki/php-1.32.0-wmf.12/includes/deferred/DeferredUpdates.php(268): MWCallableUpdate->doUpdate()
#6 /srv/mediawiki/php-1.32.0-wmf.12/includes/deferred/DeferredUpdates.php(214): DeferredUpdates::runUpdate(MWCallableUpdate, Wikimedia\Rdbms\LBFactoryMulti, string, integer)
#7 /srv/mediawiki/php-1.32.0-wmf.12/includes/deferred/DeferredUpdates.php(134): DeferredUpdates::execute(array, string, integer)
#8 /srv/mediawiki/php-1.32.0-wmf.12/includes/MediaWiki.php(913): DeferredUpdates::doUpdates(string)
#9 /srv/mediawiki/php-1.32.0-wmf.12/includes/MediaWiki.php(733): MediaWiki->restInPeace(string, boolean)
#10 [internal function]: Closure$MediaWiki::doPostOutputShutdown()
#11 {main}