Q: journal filtering and unit failures

["Ulrich Windl" <Ulrich.Windl@xxxxxxxxxxxxxxxxxxxx>]

Hi!

debugging a problem I found out some surprising fact:
When filtering the journal with "journalctl -b _SYSTEMD_UNIT=logrotate.service", I see an error only once, like this:
-- Logs begin at Mon 2020-11-30 11:35:08 CET, end at Mon 2021-12-27 10:19:31 CET. --
Dec 18 00:00:20 h16 logrotate[41799]: Failed to kill unit \x7b__SERVICE__\x7d.service: Unit \x7b__SERVICE__\x7d.s...
Dec 18 00:00:20 h16 logrotate[41799]: error: error running shared postrotate script for '/var/log/iotwatch/MD10/...

However when inspecting the full journal I also see:
Dec 18 00:00:20 h16 systemd[1]: logrotate.service: Main process exited, code=exited, status=1/FAILURE
Dec 18 00:00:20 h16 systemd[1]: Failed to start Rotate log files.
Dec 18 00:00:20 h16 systemd[1]: logrotate.service: Unit entered failed state.
Dec 18 00:00:20 h16 systemd[1]: logrotate.service: Failed with result 'exit-code'.

Actually I am surprised that those unit-related messages are not covered by the filter.
Is there a better way to get such related messages when filtering?

Also it seems that logrotate.service that should be triggered daily by a timer isn't triggered again after the error above; is that true?
(About the same question can be found in superuser.com, in case someone like to write an answer there)

(systemd-234-24.90.1.x86_64 of SLES15 SP2)

Regards,
Ulrich