Initially read this as 3600 nanometres... :-)
Air traffic failure caused by two locations 3600nm apart sharing 3-letter code
231–240 of 311 posts
Re: Air traffic failure caused by two locations 3600nm apart sharing 3-letter code
#232There's been some prior discussion on this over the past year, here are a few I found (selected based on comment count, haven't re-read the discussions yet): From the day of: https://news.ycombinator.com/item?id=37292406 - 33 points by woodylondon on Aug 28, 2023 (23 comments) Discussions after: https://news.ycombinator.com/item?id=37401864 - 22 points by bigjump on Sept 6, 2023 (19 comments) https://news.ycombinator…
There's also a much larger one, https://news.ycombinator.com/item?id=37461695 ( "UK air traffic control meltdown (jameshaydon.github.io)" , 446 comments)
I remembered this extensive article immediately (only that I've read it, not what and where to find). Thanks for saving me from endlessly searching it.
Re: Air traffic failure caused by two locations 3600nm apart sharing 3-letter code
#233I don't know how long that failure mode has been in place or if this is relevant, but it makes me think of analogous times I've encountered similar: When automated systems are first put in place, for something high risk, "just shut down if you see something that may be an error" is a totally reasonable plan. After all, literally yesterday they were all functioning without the automated system, if it doesn't seem to b…
It's been in place for a while, it happens every few months.
Re: Air traffic failure caused by two locations 3600nm apart sharing 3-letter code
#234For the people skimming the comments and are confused: 3600nm here is nautical miles, not nanometers.
My first thought was that this was some parasitic capacitance bug in a board design causing a failure in an aircraft.
Re: Air traffic failure caused by two locations 3600nm apart sharing 3-letter code
#235Earlier quoted context omitted.
Ah, chubby is a distributed lock service. Think “zookeeper” and you won’t be far off. https://static.googleusercontent.com/media/research.google.c... [pdf] Some random blog post: https://medium.com/coinmonks/chubby-a-centralized-lock-servi... You can run multiple copies/instances of chubby at the same time (like you could run two separate zookeepers). You usually run an odd number of them, typically 5. A group of chu…
Not trying to "challenge" your story, and its interesting anecdote in context. But if you have time to indulge me (and I'm not a real expert at distributed systems, which might be obvious) - Why would you have a distributed lock service that (if I read right) has multiple redundant processes that can tolerate failures... and then require clients tolerate outages? Isn't the purpose of this kind of architecture so that…
First, a global system with no outages (say the gold standard of 99.999% availability) is a promise which is basically impossible to keep.
Second, a global system being always available definitely doesn't mean it is always available everywhere. A single datacenter or even a larger region will experience both outages and network splits. It means that whatever you design on top of the super-available global system will have to deal with the global system being unavailable anyway.
TLDR is that the clients will have to tolerate outages (or at least frequent cut offs from the "global" state") anyway so it's better not to give them false promises.
Re: Air traffic failure caused by two locations 3600nm apart sharing 3-letter code
#236I guarantee that piece of code has a comment like /* This should never happen */ if (waypoints.matchcount > 2) {
Don't you mean > 1 ?
Re: Air traffic failure caused by two locations 3600nm apart sharing 3-letter code
#237FYI: nm = nautical miles, not nanometers.
And for those like myself wondering how much 3600nm is, it is of course 0.0036mm
Re: Air traffic failure caused by two locations 3600nm apart sharing 3-letter code
#238Earlier quoted context omitted.
It says ‘metric’. Good.
Indeed. There are plenty of things in aviation where they care so much about compatibility that something survives decades after it should reasonably be obsolete and replaced. Inches of mercury, magnetic bearings (the magnetic poles move! but they put up with that) and gallons of fuel, all just accepted. Got a safety-of-life emergency on an ocean liner, oil tanker or whatever? Everywhere in the entire world mandates…
Air pressure is reported in hectopascals and fuel quantity in kilograms (or tons). It's only in America where this isn't the case. We're still using feet for altitude in most places though (it's mainly Russia that uses metres).
Re: Air traffic failure caused by two locations 3600nm apart sharing 3-letter code
#239Funny airport call letters story: I once headed to Salt Lake City, UT (SLC) for a conference. My luggage was processed by a dyslexic baggage handler, who sent it to... SCL (Santiago, Chile). I was three days in my jeans at business meetings. My bag came back through Lima, Peru and Houston. My bag was having more fun than me.
Why not pop in to a shop, get another pair of pants?
Re: Air traffic failure caused by two locations 3600nm apart sharing 3-letter code
#240Earlier quoted context omitted.
It says ‘metric’. Good.
Indeed. There are plenty of things in aviation where they care so much about compatibility that something survives decades after it should reasonably be obsolete and replaced. Inches of mercury, magnetic bearings (the magnetic poles move! but they put up with that) and gallons of fuel, all just accepted. Got a safety-of-life emergency on an ocean liner, oil tanker or whatever? Everywhere in the entire world mandates…
> Inches of mercury, magnetic bearings (the magnetic poles move! but they put up with that) and gallons of fuel, all just accepted.
Here in Europe we use hectopascals for pressure, as does pretty much everywhere else. It’s important to have a magnetic bearing in case your glass dies and you’re reliant on a paper map and compass, if you didn’t plan with magnetic bearings you’d be screwed if this happened in an area of high magnetic variation.