> >> The (intended) semantics are slightly different from
> >> ~ * * * * /home/username/bin/script.sh
> >> The latter calculates the random value once when the crontab is loaded,
> >> while the former calculates it each time the crontab entry is triggered.
> >
> > Why do you need that?
>
> a) To get more randomness.
> b) To get seconds resolution instead of minutes.
>
> >> And the former achieves a resolution of seconds instead of minutes.
> >
> > Why do you need that?
>
> The original issue
> involved updates to a DDNS service where the server side had high load
How high?
> around full minutes, full 5 minutes, etc. This was most likely caused
> by bunching up of requests from cron tasks around those times.
Do you mean cron tasks running at the (many) _clients_ using that server?
> Since most hosts use NTP to synchronise their clocks,
> most of the cron-triggered tasks will run almost exactly on full minutes.
Yes. So these DDNS clients need to run their script inside every minute?
Why? What does that script do?
> So if many hosts do this the server side gets a load peak at that time.
> The object was to find a way to distribute the requests better.
I suspect you are overcomplicating it.
Why do all the clients need to run a script (inside) every minute,
and how much load does it create for the server, and why is it a problem?
> > Are you prepared for the situation when the script runs on the 59th second
> > of one minute, and on the 01th second of the next minute?
>
> Yes, I’m aware of that issue. Not so much different in concept
> than a ~/13 * * * * specifier shortening the interval at
> the end of the hour to less than the regular interval.
In concept, yes, but these runs will still be started minutes apart,
as opposed to seconds apart.
> The solution is to use a more complicated expression
That very sentence should make you stop :-)
Jan
