[mythtv-users] SystemD (Was: Recommended Linux Distro post CentOS)

[Stephen Worthington]

On Sat, 26 Dec 2020 06:27:09 -0700, you wrote:

>On Sat, Dec 26, 2020 at 10:40:17AM +0000, Mike Perkins wrote:
>> You aren't addressing the actual problem. This is not why systemd isn't
>> restarting the myth backend but why it is failing to start in the first
>> place.
>
>Well, it's reasonable certain that the reason that mythbackend doesn't start
>up is that mariadb isn't up yet.  Mariadb tells systemd that it is up before
>it really is (according to notes in Fedora's distributed file for mythbackend)
>and so systemd tries to start mythtbackend.  Since mythbackend can't connect
>to mariadb (mariadb isn't quite ready yet), mythbackend fails.  If systemd
>would just wait the Restart interval and re-try mythbackend, eventually
>mariadb would start answering and it would work.  Or, if it isn't really
>mariadb but something else that I don't have a dependency expressed for,
>eventually that would be up and things would start.  The old init (before
>systemd) would normally do this from inittab entries.  It was just annoying
>that systemd didn't seem to be willing to do this.  With very little
>information about why it wasn't.

So what did systemd tell you went wrong?  What was the output of
"journalctl -u mythbackend" immediately after boot when mythbackend
had not started?  It would probably take a reboot to collect that
information now, as the journal file with that information will likely
have long since been rolled over and deleted.

>> Granted, this can be some set of obscure systemd interactions at startup but
>> until you investigate logically you will always have the same problem.
>> 
>> I would point out that most of us have no problems starting up the
>> backend/host that contains the backend. Most difficulties seem to originate
>> at installation time, with database connections being high on the list,
>> network connections coming close. Check through as described above and see
>> what you turn up.
>
>Well, whenever I can ssh into the box, everything is up and mythbackend starts
>up just fine.  Everything the backend needs is on the same box, so shouldn't
>be any networking issue, mariadb seems the likely culprit.  The "right" way
>to specify the dependency to systemd doesn't work, and it's just not worth
>trying random hacks to poke at things to cover the race condition when it
>involves rebooting the system to test it.  Especially when the problem only
>happens once or twice a year.  It's "good enough".
>
>marcus hall
>marcus at tuells.org

You can easily have networking issues on one box - mythbackend is
known for having one in particular that requires extra systemd config
when using an external IP address instead of localhost.  So did you do
any extra systemd config for mythbackend when you changed its config
to use the external IP address?  If not, then that is the likely cause
of the problems.

We still do not know exactly what systemd and mythbackend are being
told to do.  So could you please post the output of:

systemctl cat mariadb
systemctl cat mythbackend
sudo mysql mythconverg
select * from settings where value='BackendServerAddr' or
value='MasterServerIP';
quit
ifconfig
netstat -anp | grep mysql