drbd-graceful-shutdown.service interfering with Pacemaker

[Reid Wahl]

Hi, we at Red Hat received a user bug report today involving drbd and Pacemaker.

When shutting down the system (e.g., with `shutdown -r now`),
Pacemaker hangs when trying to stop the cluster resource that manages
drbd. If the user manually stops Pacemaker before shutdown (e.g.,
`systemctl stop pacemaker`), the problem does not occur.

The user found that the systemd service drbd-graceful-shutdown is
stopping at the same time (or before) that Pacemaker is stopping the
drbd cluster resource. This is causing some interference that causes
the cluster resource stop operation to time out.

Further, the user found that the service cannot be disabled:

[root at NEWplutone2 ~]# systemctl disable drbd-graceful-shutdown.service
The unit files have no installation config (WantedBy=, RequiredBy=, Also=,
Alias= settings in the [Install] section, and DefaultInstance= for template
units). This means they are not meant to be enabled or disabled using systemctl.

Possible reasons for having this kind of units are:
• A unit may be statically enabled by being symlinked from another unit's
  .wants/ or .requires/ directory.
• A unit's purpose may be to act as a helper for some other unit which has
  a requirement dependency on it.
• A unit may be started when needed via activation (socket, path, timer,
  D-Bus, udev, scripted systemctl call, ...).
• In case of template units, the unit is meant to be enabled with some
  instance name specified.

Please advise, and consider adding a warning to the drbd documentation.

Reporter is CC'd.

-- 
Regards,

Reid Wahl (He/Him)
Senior Software Engineer, Red Hat
RHEL High Availability - Pacemaker