[RFC] conmon: add --timer-command to run command every N seconds

[giuseppe]

needed for containers/podman#27033

[giuseppe]

@jnovy PTAL

[packit-as-a-service]

Ephemeral COPR build failed. @containers/packit-build please check.

[Luap99]

This will not work for podman, there are normal healthchecks and startup healthchecks which can use a different interval each and only podman knows when to switch. I think this needs some larger design discussion if we would want to do it in conmon.
And if we are working towards a conmon rust rewrite does it even make sense to add such feature now in the old c version?

[mheon]

Concur - without some sort of signaling mechanism to indicate that we are finishing the startup healthcheck and switching to the new parameters, this will not work. Adding that seems like a lot of work for something we're not even sure we want to do (moving HCs into Conmon)

[giuseppe]

Yes this is not complete implementation, just a couple of hours of work to realize better what is doable and if it is even worth it. Handling different intervals is possible and timers can be unregistered (missing now).

Said so, I am still not sure it is worth doing and would leave it as a systemd only feature