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Nelson's Weblog



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Updated: 2017-01-19T01:00:00Z

 



Reed College D-Lab

2017-01-19T01:00:00Z




Leap Second 2016-12-31

2017-01-03T00:38:00Z

(image) The Internet mostly survived the leap second two days ago. I’ve seen three confirmed problems. Cloudflare DNS had degraded service; they have an excellent postmortem. Some Cisco routers crashed. And about 10% of NTP pool servers failed to process the leap second correctly.

We’ve had a leap second roughly every two years. They often cause havoc. The big problem was in 2012 when a bunch of Java and MySQL servers died because of a Linux kernel bug. Linux kernels died in 2009 too. There are presumably a lot of smaller user application failures too, most unnoticed. Leap second bugs will keep reoccurring. Partly because no one thinks to test their systems carefully against weird and rare events. But also time is complicated.

Cloudflare blamed a bug in their code that assumed time never runs backwards. But the real problem is POSIX defines a day as containing exactly 86,400 seconds. But every 700 days or so that’s not true and a lot of systems jump time backwards one second to squeeze in the leap second. Time shouldn’t run backwards in a leap second, it’s just a bad kludge. There are some other options available, like the leap smear used by Google. The drawback is your clock is off by as much as 500ms during that day.

The NTP pool problem is particularly galling; NTP is a service whose sole purpose is telling time. Some of the pool servers are running openntpd which does not handle leap seconds. IMHO those servers aren’t suitable for public use. Not clear what else went wrong but leap second handling has been awkward for years and isn’t getting better.




Geographic art gifts

2016-12-01T18:28:00Z

I like maps. Some friends and colleagues are making some beautiful map and geographic based art that would make nice Christmas gifts. (For others! I’m not hinting, have these already!)

Bill Morris makes painterly prints of satellite photographs. You can read about his process in detail. In short, he takes satellite images from Planet Labs and then pushes them through customized machine learning software to render them like paintings. They’re beautiful.

Rachel Binx makes geographic style products. Jewelry, clothing, and posters all custom made for someone’s personal geography. One-off design and fabrication like this is really ambitious and she delivers well.

Benjamin Grant of the Daily Overview blog has a new coffee table book of aerial and satellite imagery. It sounds simple but he has an excellent eye and editor’s hand. It’s lovely.

Jared Prince of Muir Way made a high quality print of a map of American rivers. He was inspired by my river map but ended up recreating the whole thing from scratch with a much better result than mine. The print quality is excellent too.




Ken's hardboiled egg dip

2016-11-25T19:19:00Z




Dakota Pipeline maps

2016-11-21T20:13:00Z

Interesting pair of maps showing the route of the controversial Dakota Access Pipeline

The upper map is the official map from Energy Transfer Partners. It is remarkably free of detail. Enter Carl Sack's map below, which contains a lot more detail and was designed explicitly to help oppose the pipeline. It's objectively a better map in many ways, particularly showing the locations of rivers and the Sioux Reservation.

It's also notable that Sack includes the "Unceded Sioux Territory". My understanding (and I could be wrong) is that land has disputed legal status today, the result of a broken treaty with the Sioux. The passing of this pipeline through that land is a key part of the dispute, though, and mapping it helps us understand the protest against the pipeline's passage through that land.




Preserving free and fair elections

2016-11-18T20:32:00Z







Do not normalize Trump

2016-11-15T22:31:00Z




iPhones can't receive SMS reliably

2016-10-13T14:29:00Z




Oktoberfest crowd tricks

2016-09-29T07:52:00Z