[systemd-devel] SystemD dependency problem

[Michael Biebl]

In addition to what Mantas said, I'd suggest reading man systemd.special.
and https://www.freedesktop.org/wiki/Software/systemd/NetworkTarget/

This should give you an idea what network-online.target is supposed to be.
It's not a target to hook arbitrary services into (via WantedBy).
Your service looks like multi-user.target is a better fit.

Stuff like NetworkManager-wait-online.service or
systemd-networkd-wait-online.service is something which should hook
into network-online.target via WantedBy.


Am Di., 22. Dez. 2020 um 14:17 Uhr schrieb Mantas Mikulėnas <grawity at gmail.com>:
>
> On Tue, Dec 22, 2020 at 1:36 PM Ronald Wimmer <ronaldw at ronzo.at> wrote:
>>
>> On a server running OL 7.9 with SystemD 219 we have a custom SystemD
>> service we have something like
>>
>>
>> [Unit]
>> Requires=network.target docker.service
>>
>> [Service]
>> Restart=always
>> RestartSec=10
>> TimeoutSec=300
>> WorkingDirectory=/data/someapplication
>> ExecStartPre=<pull a docker image>
>> ExecStart=<docker-compose up>
>> ExecStop=<docker-compose stop>
>> ExecStopPost=<docker-compose down>
>>
>> [Install]
>> WantedBy=network-online.target
>>
>> which does not work. This service leads do several other services
>> (rsyslogd, docker, network-online.target, ...) to be stuck in "start
>> waiting".
>>
>> My question is why? Is there any obvious misconfiguration in the service
>> above I am too blind to see?
>
>
> As a special case, when a target has Wants= for some unit, it will automatically add an After= as well. (So from your unit's point of view, you have [Install] WantedBy=network-online.target, so you can imagine that you automatically have a Before=network-online.target as well – unless you explicitly specify the opposite.)
>
> However, Docker has "After=network-online.target", so you end up creating an ordering loop:
>
> * yourthing.service has no After=, but it runs `docker` commands and cannot finish until docker.service is up;
> * docker.service explicitly has After=network-online.target and won't start until that target is reached;
> * but network-online.target has an implicit After=yourthing.service (as explained above).
>
> --
> Mantas Mikulėnas
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