[systemd-devel] [RFC] runtime configurable timer

[WaLyong Cho]

On 09/12/2014 12:54 AM, David Herrmann wrote:
> Hi
> 
> On Thu, Sep 11, 2014 at 10:45 AM, WaLyong Cho <walyong.cho at samsung.com> wrote:
>> (I will happy there is already similar method already exist.)
>>
>> systemd already has similar functionality "systemd-run" but that is only
>> for scope or service unit. I think that is useful run a service without
>> unit file on permanent storage.
>>
>> As a similar method, is it possible to generate or configure timer unit
>> on runtime?
>>
>> Honestly, now, I need a runtime configurable timer interface. If systemd
>> has this then I can reduce one of daemon.
> 
> Something like at(1)? That is, executing a command at a later time?
> 

Yes, exactly right.

> Currently, timer units do not support transient units. So to implement
> something like systemd-at, you'd first have to add support for that,
> then you can make systemd-run do this. I don't think anyone has worked
> on this so far.
> 

Before start working it, we need some of discussion about how make the
transient unit. I think we have two options.
One is, as you said, make systemd-at and the other is add option to
systemd-run. (e.g. --OnCalendar=, --OnActiveSec= or so)
If we choose the former, then we should consider how load the relate
unit(service). Because, the timer unit is not working alone. It related
with service unit. So, if the transient timer unit related with already
existing service then it will not much complicate. But if we want to add
both transient timer and transient service then it will more complicate.
In latter case, I think, it is more easier. Because, we can get a all of
information to make two transient service transient timer. But
internally we should call StartTransientUnit method call to start the
timer unit and AddTransientUnit(or LoadTransientUnit(?)) to add service
unit what will be started by the timer unit.

Any other ideas?

WaLyong

> Thanks
> David
>