<ankry> Hmm, what does it mean:
<ankry> I got NULL instead of page content
<nadando> Does anyone know why this page just says NULL https://en.wiktionary.org/wiki/Wiktionary:Tea_room/2016/March
<p858snake> nadando / ankry: are you currently logged in?
<nadando> p858snake, yes
<Waggie> p858snake, we just had another user report the same thing on https://en.wikipedia.org/wiki/Australian_rules_football
<Waggie> (over on -en-help)
<p858snake> try doing a force refreshed (most browsers: Ctrl+F5
<Waggie> They've left, so I can't inquire further.
<p858snake> *forced refresh
<nadando> That page says NULL too, same if I log out and force refresh
<p858snake> Can you take a screenshot please?
<Waggie> I get NULL also, Chrome, logged in, on Linux. Will take screenshot momentarily.
<Waggie> Also, page source consists only of "NULL". No html, or anything.
Somehow "NULL" got cached in varnish.
legoktm@terbium:~$ echo "https://commons.wikimedia.org/wiki/Special:RecentChanges" | mwscript purgeList.php --wiki=commonswiki Purging 1 urls Done!
And the url works now.
Users are reporting this at Special:Watchlist, Special:Random, Special:Contributions, Special:Block as well as articles.
I just found out that three out of four of the application servers dedicated to debugging were still pooled to serve traffic. If someone was performing some tests on those, the assumption that tests would not impact production would be voided.
This hypothesis came to my mind as @Legoktm suggested on irc
< legoktm> NULL in all uppercase suggests a "var_dump(null)" or something
earlier this morning. It's completely unverified, but I'm fixing the potential issue anyways as this could be a real-world scenario.