ReleaseTaggerBot tagged T297664 with MW-1.38-notes (1.38.0-wmf.16; 2022-01-03), but the only associated patch made it into wmf.13. The patch was merged at 01:52 UTC, the bot updated the task at 02:00 UTC, and the branch commit is timestamped 02:07 UTC, so this could be a timing issue / race condition.
(BTW, the deployments page on wikitech is wrong: it claims that the branch cut happens at 03:00 UTC)
Entirely guessing, the branch in Gerrit was created at 02:00 UTC, RTB did not see this patch in that branch, tagged it as going in wmf.16, and then the commit for that branch was only pushed at 02:07 UTC.
We could adjust the cron to run every hour at 30 minutes instead of on the hour to avoid this since train branching is now on a pretty reliable schedule.
(BTW, the deployments page on wikitech is wrong: it claims that the branch cut happens at 03:00 UTC)
DST bug maybe? That page is generated by https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/tools/release/+/refs/heads/master/make-deployment-calendar/deployments-calendar.json
From the log file:
2021-12-14 02:00:23,050 - forrestbot - INFO - Processing https://gerrit.wikimedia.org/r/c/mediawiki/extensions/MediaSearch/+/746979 2021-12-14 02:00:23,050 - root - DEBUG - Requesting 'master' branches for mediawiki/extensions/MediaSearch 2021-12-14 02:00:23,065 - urllib3.connectionpool - DEBUG - https://gerrit.wikimedia.org:443 "GET /r/projects/mediawiki%2Fextensions%2FMediaSearch/branches/ HTTP/1.1" 200 1455 2021-12-14 02:00:23,066 - forrestbot - INFO - https://gerrit.wikimedia.org/r/c/mediawiki/extensions/MediaSearch/+/746979: merged in branch master, Task 297664, needs slugs ['mw1.38.0-wmf.14']
now, how does RTB figure out the slug for a master branch commit?
By getting a list of branches from Gerrit, finding the latest release branch, and adding 1 to the wmf-part:
https://github.com/wikimedia/labs-tools-forrestbot/blob/master/forrestbot.py#L47
So what I think happened is the following:
Which suggests that moving to 30 minutes will make the issue worse, not better. The only way to correctly fix this would be to verify whether the commit is part of the 'current' release branch.... maybe through https://gerrit-review.googlesource.com/Documentation/rest-api-projects.html#get-included-in ? There's of course still a potential for a race condition then, but it's at least limited to a few seconds rather than 5 minutes.