Real-world example:

1) Unit `ovs-vswitchd.service` took 2 minutes to start up.
2) That delayed `network.target` (`ovs-vswitchd.service` has `Before=network.target`).
3) That delayed `tgt.service` too (it has `After=network.target`).

4) BUT that did _not_ delay `cinder-volume.service` (it does _not_ have `After=tgt.service`)
5) So it failed to talk to tgtd with tgtadm, and volume re-export failed.

 $ cat sos_commands/logs/journalctl_--no-pager_--catalog_--boot \
   | grep -E -B1 'Subject: Unit (cinder-volume.service|tgt.service|ovs-vswitchd.service|network.target)'

 Aug 10 06:23:15 <HOST> systemd[1]: Started OpenStack Cinder Volume.
 -- Subject: Unit cinder-volume.service has finished start-up
 --
 <<< ERROR in cinder-volume.log >>>

 Aug 10 06:23:16 <HOST> systemd[1]: Starting Open vSwitch Forwarding Unit...
 -- Subject: Unit ovs-vswitchd.service has begun start-up
 --
 <<< DELAY of 2 minutes >>>

 Aug 10 06:25:17 <HOST> systemd[1]: Started Open vSwitch Forwarding Unit.
 -- Subject: Unit ovs-vswitchd.service has finished start-up
 --
 Aug 10 06:25:17 <HOST> systemd[1]: Reached target Network.
 -- Subject: Unit network.target has finished start-up
 --
 Aug 10 06:25:17 <HOST> systemd[1]: Starting (i)SCSI target daemon...
 -- Subject: Unit tgt.service has begun start-up
 --
 Aug 10 06:25:19 <HOST> systemd[1]: Started (i)SCSI target daemon.
 -- Subject: Unit tgt.service has finished start-up

 <<< NOW tgtd is running >>>

@ var/log/cinder/cinder-volume.log

  9901 2022-08-10 06:23:21.515 3939 INFO cinder.service [-] Starting cinder-volume node (version 12.0.9)
 ...
  9932 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager [req-e67a852a-6cce-4073-a2de-d3487c85d586 - - - - -] Failed to re-export volume, setting to ERROR.: ProcessExecutionError: Unexpected error while running command.
  9933 Command: sudo cinder-rootwrap /etc/cinder/rootwrap.conf tgtadm --lld iscsi --op show --mode target
  9934 Exit code: 107
  9935 Stdout: u''
  9936 Stderr: u'tgtadm: failed to send request hdr to tgt daemon, Transport endpoint is not connected\n'
  9937 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager Traceback (most recent call last):
  9938 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager File "/usr/lib/python2.7/dist-packages/cinder/volume/manager.py", line 486, in init_host
  9939 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager self.driver.ensure_export(ctxt, volume)
  9940 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager File "/usr/lib/python2.7/dist-packages/cinder/volume/drivers/lvm.py", line 826, in ensure_export
  9941 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager self.target_driver.ensure_export(context, volume, volume_path)
  9942 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager File "/usr/lib/python2.7/dist-packages/cinder/volume/targets/iscsi.py", line 261, in ensure_export
  9943 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager old_name=None, **portals_config)
  9944 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager File "/usr/lib/python2.7/dist-packages/cinder/utils.py", line 818, in _wrapper
  9945 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager return r.call(f, *args, **kwargs)
  9946 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager File "/usr/lib/python2.7/dist-packages/retrying.py", line 206, in call
  9947 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager return attempt.get(self._wrap_exception)
  9948 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager File "/usr/lib/python2.7/dist-packages/retrying.py", line 247, in get
  9949 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager six.reraise(self.value[0], self.value[1], self.value[2])
  9950 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager File "/usr/lib/python2.7/dist-packages/retrying.py", line 200, in call
  9951 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager attempt = Attempt(fn(*args, **kwargs), attempt_number, False)
  9952 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager File "/usr/lib/python2.7/dist-packages/cinder/volume/targets/tgt.py", line 141, in create_iscsi_target
  9953 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager run_as_root=True)
  9954 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager File "/usr/lib/python2.7/dist-packages/cinder/utils.py", line 126, in execute
  9955 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager return processutils.execute(*cmd, **kwargs)
  9956 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager File "/usr/lib/python2.7/dist-packages/oslo_concurrency/processutils.py", line 424, in execute
  9957 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager cmd=sanitized_cmd)
  9958 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager ProcessExecutionError: Unexpected error while running command.
  9959 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager Command: sudo cinder-rootwrap /etc/cinder/rootwrap.conf tgtadm --lld iscsi --op show --mode target
  9960 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager Exit code: 107
  9961 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager Stdout: u''
  9962 2022-08-10 06:23:23.398 3932 ERROR cinder.volume.manager Stderr: u'tgtadm: failed to send request hdr to tgt daemon, Transport endpoint is not connected\n'