Hiya!
I halted the train this afternoon. tl;dr: I rolled wmf.20 to group1 and I saw a huge spike in DB replag and Cirrus errors. Rolling back made them go away!
There are tasks: https://phabricator.wikimedia.org/T186765 https://phabricator.wikimedia.org/T186764
I think Eric/Stas already fixed the Cirrus bug. The other one was temporally related, but I dunno about causally.
Needs more investigation if we want to roll forward tomorrow!
<3
-Chad