[systemd-devel] OnCalendar timer starts before the scheduled date has passed

[Andrei Borzenkov]

04.03.2019 21:19, Alden Page пишет:
> Hi systemd team,
> 
> I'm having some trouble understanding the behavior of a systemd timer I've
> set up in systemd version 219. I have a task that I want to run once per
> week on Sundays at 3:00am UTC. However, as soon as I do `systemctl start
> my_timer.timer`, the task starts no matter what time it is. This is a

That is what you told it to do.

> problem for me, because that means that my timer starts every single time I
> recreate my server's virtual machine. After the initial erroneously
> scheduled job has completed successfully, the timer starts behaving
> correctly and runs on Sundays at 3:00am UTC.
> 
> Here is how I've set up my timers. This is an excerpt from the script I use
> to bootstrap my VMs:
> 
> # Schedule weekly ingest of new data
> cat << EOF > /etc/systemd/system/ingest_upstream.service
> [Unit]
> Description=Load and index image data from upstream.
> [Service]
> ExecStart=/usr/bin/curl -XPOST localhost:8001/task -H "Content-Type:
> application/json" -d '{"model": "image", "action": "INGEST_UPSTREAM"}'
> EOF
> 
> cat << EOF > /etc/systemd/system/ingest_upstream.timer
> [Unit]
> Description=Ingest data from upstream every Sunday at 8:00am EST (3:00am
> UTC).
> Requires=ingest_upstream.service
> 

Requires means - when ingest_upstream.timer is started (activated) also
start (activate) units listed here. Which is exactly what happens.

> [Timer]
> OnCalendar=Sun *-*-* 3:00:00
> Unit=ingest_upstream.service
> 
> [Install]
> WantedBy=timers.target
> EOF
> systemctl start ingest_upstream.timer
> 
> After `systemctl start`, shouldn't it wait until the next OnCalendar
> interval has passed, particularly since `Persistent=...` is not set?
> 

It (presumably ingest_upstream.timer) does wait; your service is not
activated by timer but by basic systemd unit dependency.