Comment 7 for bug 1784757

Hmm, the same took 1 second for me.

root@b:~# systemctl status rabbitmq-server
● rabbitmq-server.service - RabbitMQ Messaging Server
   Loaded: loaded (/lib/systemd/system/rabbitmq-server.service; enabled; vendor preset: enabled)
   Active: inactive (dead) since Fri 2019-05-10 07:16:00 UTC; 5s ago
  Process: 6004 ExecStop=/usr/sbin/rabbitmqctl stop (code=exited, status=0/SUCCESS)
  Process: 5348 ExecStart=/usr/sbin/rabbitmq-server (code=killed, signal=TERM)
 Main PID: 5348 (code=killed, signal=TERM)

May 10 07:15:40 b systemd[1]: Starting RabbitMQ Messaging Server...
May 10 07:15:41 b rabbitmq[5349]: Waiting for rabbit@b
May 10 07:15:41 b rabbitmq[5349]: pid is 5365
May 10 07:15:43 b systemd[1]: Started RabbitMQ Messaging Server.
May 10 07:15:43 b systemd[1]: rabbitmq-server.service: Failed to reset devices.list: Operation not permitted
May 10 07:15:59 b systemd[1]: Stopping RabbitMQ Messaging Server...
May 10 07:15:59 b rabbitmq[6004]: Stopping and halting node rabbit@b
May 10 07:16:00 b systemd[1]: Stopped RabbitMQ Messaging Server.

Do you have any config changes or ongoing messages running while this shutdown happens that might explain and lead us to the root cause?

The stop action is just:
  $ /usr/sbin/rabbitmqctl stop

You might change the loglevel [1] and then in a second console attach to the log to see what is going on in that time?

[1]: https://www.rabbitmq.com/logging.html