When viewing https://test2.wikipedia.org/wiki/1968年臺灣 in codfw (mw2099.codfw.wmnet) I noticed the following
Original exception: [1ececc4b] /wiki/1968%E5%B9%B4%E8%87%BA%E7%81%A3 DBReadOnlyError from line 789 of /srv/mediawiki/php-1.27.0-wmf.16/includes/db/Database.php: Database is read-only: Mediawiki is in read-only mode during maintenance, please try again in 15 minutes Backtrace: #0 /srv/mediawiki/php-1.27.0-wmf.16/includes/db/Database.php(1463): DatabaseBase->query(string, string) #1 /srv/mediawiki/php-1.27.0-wmf.16/extensions/ShortUrl/ShortUrl.utils.php(54): DatabaseBase->insert(string, array, string, string) #2 /srv/mediawiki/php-1.27.0-wmf.16/extensions/ShortUrl/ShortUrl.hooks.php(44): ShortUrlUtils::encodeTitle(Title) #3 /srv/mediawiki/php-1.27.0-wmf.16/includes/Hooks.php(195): ShortUrlHooks::addToolboxLink(VectorTemplate, boolean) #4 /srv/mediawiki/php-1.27.0-wmf.16/skins/Vector/VectorTemplate.php(319): Hooks::run(string, array) #5 /srv/mediawiki/php-1.27.0-wmf.16/skins/Vector/VectorTemplate.php(273): VectorTemplate->renderPortal(string, array, string, string) #6 /srv/mediawiki/php-1.27.0-wmf.16/skins/Vector/VectorTemplate.php(195): VectorTemplate->renderPortals(array) #7 /srv/mediawiki/php-1.27.0-wmf.16/includes/skins/SkinTemplate.php(240): VectorTemplate->execute() #8 /srv/mediawiki/php-1.27.0-wmf.16/includes/OutputPage.php(2363): SkinTemplate->outputPage() #9 /srv/mediawiki/php-1.27.0-wmf.16/includes/MediaWiki.php(746): OutputPage->output() #10 /srv/mediawiki/php-1.27.0-wmf.16/includes/MediaWiki.php(519): MediaWiki->main() #11 /srv/mediawiki/php-1.27.0-wmf.16/index.php(43): MediaWiki->run() #12 /srv/mediawiki/w/index.php(3): include(string) #13 {main} Exception caught inside exception handler: [0b006398] /wiki/1968%E5%B9%B4%E8%87%BA%E7%81%A3 DBReadOnlyError from line 789 of /srv/mediawiki/php-1.27.0-wmf.16/includes/db/Database.php: Database is read-only: Mediawiki is in read-only mode during maintenance, please try again in 15 minutes Backtrace: #0 /srv/mediawiki/php-1.27.0-wmf.16/includes/db/Database.php(1463): DatabaseBase->query(string, string) #1 /srv/mediawiki/php-1.27.0-wmf.16/extensions/ShortUrl/ShortUrl.utils.php(54): DatabaseBase->insert(string, array, string, string) #2 /srv/mediawiki/php-1.27.0-wmf.16/extensions/ShortUrl/ShortUrl.hooks.php(44): ShortUrlUtils::encodeTitle(Title) #3 /srv/mediawiki/php-1.27.0-wmf.16/includes/Hooks.php(195): ShortUrlHooks::addToolboxLink(VectorTemplate, boolean) #4 /srv/mediawiki/php-1.27.0-wmf.16/skins/Vector/VectorTemplate.php(319): Hooks::run(string, array) #5 /srv/mediawiki/php-1.27.0-wmf.16/skins/Vector/VectorTemplate.php(273): VectorTemplate->renderPortal(string, array, string, string) #6 /srv/mediawiki/php-1.27.0-wmf.16/skins/Vector/VectorTemplate.php(195): VectorTemplate->renderPortals(array) #7 /srv/mediawiki/php-1.27.0-wmf.16/includes/skins/SkinTemplate.php(240): VectorTemplate->execute() #8 /srv/mediawiki/php-1.27.0-wmf.16/includes/OutputPage.php(2363): SkinTemplate->outputPage() #9 /srv/mediawiki/php-1.27.0-wmf.16/includes/exception/MWException.php(204): OutputPage->output() #10 /srv/mediawiki/php-1.27.0-wmf.16/includes/exception/MWException.php(244): MWException->reportHTML() #11 /srv/mediawiki/php-1.27.0-wmf.16/includes/exception/MWExceptionHandler.php(69): MWException->report() #12 /srv/mediawiki/php-1.27.0-wmf.16/includes/exception/MWExceptionHandler.php(180): MWExceptionHandler::report(DBReadOnlyError) #13 /srv/mediawiki/php-1.27.0-wmf.16/includes/MediaWiki.php(528): MWExceptionHandler::handleException(DBReadOnlyError) #14 /srv/mediawiki/php-1.27.0-wmf.16/index.php(43): MediaWiki->run() #15 /srv/mediawiki/w/index.php(3): include(string) #16 {main}
Aside from the fact that something is trying to do a write on a page view, over GET, in read-only mode, and not catching it - the error that does bubble is breaking the page layout. Seems like it happens very late in the request cycle but still before the response is closed, so the user gets two (or three) full html responses mixed up on top of each other.