Due to an outage on enwiki earlier today caused by Special:AllPages, it has temporarily
been disabled on all wikis pending further investigation.
To this extent a public tracking task [1] has been created, and updates will be put there
to keep people in the loop.
Proper incident should appear on Wikitech at a later date, after the problem has been
resolved.
Sam
[1]
https://phabricator.wikimedia.org/T160916