@shaknais Even if it were available, it seems to randomise by whole minutes, so not potentially easing the problem in this article.
"The RANDOM_DELAY variable allows delaying job startups by random amount of minutes with upper limit specified by the variable."
My current server cron is Vixie, which does not support this feature.
Not following. If it randomises by minutes, that flattens the curve, over minutes, and avoids the thundering herd problem.
How would it not?
@shaknais This article refers to things happening (such as CPU use) at the start of each minute. Merely picking a random minute does not make that particular problem go away. Picking a random second within each minute would. (Better still to pick a random very-fine-grained sub-mains-cycle time to avoid creating a new start-of-second surge problem.)
@DamonHD Unless everyone picked the same minute, by not seeding their random, you'd be correct.
But, everyone has a different minute. And each task has a different minute.
@shaknais The problem is that the first few seconds of an average minute have a higher load (see the charts in the Nature paper). Spreading across random minutes helps at other levels, but does not eliminate this feature. When looking at the 1/60Hz spectrum, and eg worrying about mechanical wear on physical turbines, it does not matter much in *which* minutes those early-second surges happen, just that they do happen.
@DamonHD Okay... It doesn't matter which minute, so long as that minute is commonly chosen by _everyone_.
Otherwise you could say it spreading across hours wouldn't flatten the curve - a logical fallacy.
Because of jitter, not everyone is choosing the same moment. Which means there is a lesser load, and a more distributed load, that gracefully increases, and decreases.
If you spread across the 5m interval, it would disappear into the graphs noise.
@shaknais Synchronised extra work in the start of ANY minute, as fired off by EVERY cron on the planet, will add to *this* problem. Cron (as I have ever used) does not add jitter to its wakeup on the minute, whichever minute that is. (Picking random minutes does reduce *other* problems.)
To be clear: 1/60Hz spikes are independent of 1/3600Hz spikes etc: they should both be dealt with, but have to dealt with separately.
@DamonHD How would spreading the start time of processes, across 60 new units, instead of 1, suddenly increase load?
How do you get _more_ from _less_? You're distributing.
If what you're saying is true, then PFR wouldn't be working in Australia, because that only spreads across 4-seconds for the 1/50Hz. But it is working.
@shaknais Independent frequency components are independent. I don't know how to say this in other ways.
Spreading the start time from the start of minute 0 to the start of minute X where X is randomly 0, 1, 2, ... 59 (in each case a whole number) still results in average extra load across the hour of the same amount in the start of an average minute.
@DamonHD Okay... So what the article says Australia is doing and working for dealing with the problem, isn't dealing with the problem. Got it.
@shaknais They are containing the problem by making the rest of the system work harder to suppress it, but not removing it at source.
Did you look at the linked to Nature paper? It's moderately readable, and explains this better than I am.
"These developments demonstrate that the recurrent 1-min oscillation already has operational relevance, even though current mitigation strategies primarily address amplification rather than the underlying source."