Bug#997943: systemd: Persistent attribute of timer is ignored

[Michael Biebl]

On 28.10.21 09:05, Hendrik Buchner wrote:
> Hello Michael and Julian,
> 
> that explains why the behaviour of "RandomizedDelaySec" together with
> "Persistent" is different between buster and bullseye. If that's the
> intended behaviour, my systems seems to work like they should and it's
> no bug.

It's definitely a change of behaviour I wasn't aware of myself.

While it fixes the thundering herd issue during boot, it is definitely 
problematic that for systems that aren't up for a longer period of time, 
a timer with a large RandomizedDelaySec= will basically never fire.

I do think that we have a similar thundering herd issue with timers that 
elapse while the system is suspended and ttbomk, systemd will *not* 
reapply a RandomizedDelaySec= on resume.

This appears to be inconsistent imho.

Somehow I think systemd could be more clever here and scale down 
RandomizedDelaySec= on boot depending on how far in the past the 
timestamp of the stampfile is.
Say the last activation of the service was 12 hours ago, then scale down 
RandomizedDelaySec=12h by dividing it by 12, so it would become 
RandomizedDelaySec=1h. The further in the past, the shorter the delay 
would become and the more likely that the timer fires eventually.

And for consistencies sake, a (scaled) RandomizedDelaySec=1 should also 
be reapplied on resume.



Regards,
Michael
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