[systemd-devel] Can service of timers.target having After=multi-user.target create a loop?

[Amish]

On 13/07/20 2:07 am, Uoti Urpala wrote:

> On Sun, 2020-07-12 at 17:13 +0300, Andrei Borzenkov wrote:
>> 12.07.2020 16:21, Amish пишет:
>>> I have a timer file like this:
>>>
>>> [Unit]
>>> Description=Foo
>>> After=multi-user.target
>>>
>>> [Timer]
>>> OnCalendar=*:0/5
>>> Persistent=false
>>>
>>> [Install]
>>> WantedBy=timers.target
>>>
>>>
>>> Because AFAIK timers.target runs before multi-user.target. But here
>>> something inside timers.target waits for multi-user.target.
>>>
>>> So how does systemd resolve this loop?
>>>
>> There is no loop. There is no transitive dependency between timer unit
>> and service unit. Timer unit gets started early and enqueues start job
>> for service unit; this start job waits for multi-user.target according
>> to After dependency. Mulitple invocation of timer will try enqueue start
>> job again which will simply be merged with existing pending request.
> But shouldn't the After line be in the .service file, not the timer, in
> this case? The timer should be ready early if it's activated by
> timers.target, the service should wait before running.
>
I have put it in .timer file and works as expected.

Jul 13 10:38:27 server1 systemd[1]: Reached target Multi-User System.
Jul 13 10:38:27 server1 systemd[1]: Started Foo. (the timer activated)
Jul 13 10:38:27 server1 systemd[1]: Reached target Timers.
...
Jul 13 10:40:01 server1 systemd[1]: Starting Foo... (the service that 
runs at */5)
Jul 13 10:40:01 server1 systemd[1]: foo.service: Succeeded.
Jul 13 10:40:01 server1 systemd[1]: Finished Foo.

Regards

Amish