At least I realized I did something wrong and closed the browser before everyone got removed, but looks like those with email A to somewhere in K got... nuked.

This is a massive UX problem, not you-problem. Many people accidentally clicked on it including yours truly. We can restore it from backups. I will ping @jcrespo for this and we can get it fixed. No worries.

Hey, @revi, no worries. Could you confirm with me a timestamp when members would be good? 2024-11-11 06:20:00? A little earlier, at 06:00:00 ?

I was able to pin down the undesired mass deletion starting at:

# at 906744201
#241111  6:21:17 server id 171966607  end_log_pos 906744243 CRC32 0xeb3133f4    GTID 171966607-171966607-71484404 trans

and finishing at:

#241111  6:23:21 server id 171966607  end_log_pos 939288298 CRC32 0x0afae230    Xid = 27077268418
COMMIT/*!*/;
# at 939288298

I was going to to a partial point in time recovery, but I think it will be easier to just revert those DELETIONs, reinserting the rows for membership and preferences.

It seems to me not all members were deleted, while I can see some people subscribing manually, only around 300 are missing ATM.

I only found 642 deleted users between the dates above, about to reinsert them.

Mentioned in SAL (#wikimedia-operations) [2024-11-11T13:22:35Z] <jynus> reverting deleted rows on db1176 (mailman3) T379519

root@db1176[mailman3]> SELECT count(*) FROM member where list_id = 'commons-l.lists.wikimedia.org';
+----------+
| count(*) |
+----------+
|     1295 |
+----------+
1 row in set (0.006 sec)

The revert has been done, with the following comments:

• People have been silently resubscribed, no action needed. As an example, I was unsubscribed, and I now appear resubscribed:

• Membership to the commons-l.lists.wikimedia.org and user list preferences have been restored, but only if user hasn't manually rejoined or changed their preferences. If someone joined manually, they would have reset their list preferences (language, etc), and in those cases we haven't overridden them. Also, if there was some change from users or admins since then that hasn't been reverted or reapplied (e.g. adding admin provileges), so expect some confusion there. For example, if someone unsubscribed or resuscribed and unsuscribed, they may end up silently subscribed. Other than that, the ~321 accidentally unsubscribed users have been subscribed again.

Please @revi if you can summarize in a more user-friendly terms as a list admin, that would be appreciated. In theory, this is now fixed.

I need to do some cleanup, but this is almost resolved, except for communication and checking it worked as expected.

Change #1089831 had a related patch set uploaded (by Jcrespo; author: Jcrespo):

[operations/software@master] Add quick and dirty script to revert accidental mailman unsubscriptions

https://gerrit.wikimedia.org/r/1089831

Thank you @jcrespo 😍