[LEAPSECS] Leapseconds, more evidence

Rob Seaman seaman at noao.edu
Mon Jul 2 17:30:07 EDT 2012

Zefram wrote:

> Hourly cron jobs. Most people are idiots and schedule them all for the

> top of the hour. The graph also shows discernible regular peaks for

> aligned cycles of 30, 15, 10, and 5 minutes. Of course, for the same

> reason, daily cron jobs are mst often scheduled for midnight, so it's

> expected that there be an especially big peak at midnight.

Good point. Though at an observatory the midnight issue often translates to noon.

Interesting notion about dithering crontab and init scheduling in general. Grabbing a crontab from a random server here - one that likely several folks have added to - many entries are on even cycles, but there are some interesting choices like 47 minutes after the hour, or activities in the middle of the afternoon.

I was taken by the 17 minute cycle quoted for one of the issues in several reports (though perhaps borrowing from the same source). Anybody know what that was about? Something that was programmed in, or emergent behavior like locusts?

> I'd like to see a normal midnight's graph as well, because that's a confounding

> effect that complicates interpretation of this graph.


> The downward trend seen in the hours following midnight rather resembles

> the smaller downward trend seen within each hour. Particularly obvious

> in the last three hours before UT midnight, but visible in nearly every

> hour, there's a long-lived jump at the top of each hour, at the same

> time as (but distinct from) the short-lived hourly peak. Is this the

> normal structure at that scale?

The version on google+ is a bit more readable. Not sure how much analysis is useful without more context.


More information about the LEAPSECS mailing list