apt mirror `ftp.jaist.ac.jp` is not available anymore

[DarkTrick]

Apt configuration:
- standard buster configuration (unchanged)

Problem:
- Impossible to upgrade / install software (`apt update` works)

Error:
- Cannot connect to ftp.jaist.ac.jp

My guess:
- raspberrypi.org (target of apt) has ftp.jaist.ac.jp configured as mirror for certain countries. However, that mirror is not available anymore.
- I cannot find any local configuration of `ftp.jaist.ac.jp`.

[peter green (plugwash)]

Seems to be working for me.

Are you still having difficulties?
What country are you in?
What ISP are you using?

[DarkTrick (darktrick1337)]

I don't have a pi to 100% verify anymore, but their site is working again, so I guess apt will work too. This very problem is cured.

I want to note, that the server was at least down for 1 - 2 weeks. Possibly longer.

I think apt should've automatically change to a different mirror. Is there a reason it didn't? Is that
(1) apt behavior?
(2) a static setting on the rpi?
(3) a static setting on the rpi repository server?

[peter green (plugwash)]

Unfortunately while the server setup we use has the ability to send details of multiple mirrors, apt has no way to make use of that information.

If the server really was completely down, then we have systems in place that should take the mirror out of service, but that doesn't help if your ISP and the ISP hosting the mirror have a connectivity issue with each other, while retaining connectivity to our servers in the UK. This is particularly an issue in Asia where providers often have better connectivity to the west than they do to each other.

[DarkTrick (darktrick1337)]

TBH, I don't really understand the details nor the implications of that information.

I would expect the system to have some communication in place like this:

1) Apt: Server, hand me your data.
2) Server: I will give you this mirror; get your data there.
3) Apt: Ok.
4) Apt: Mirror server, please hand me your data.
5) Mirror server: ...
6) [apt: hmm.. mirror is no available.]
7) Apt: Server, mirror is not available, please give me another mirror. ( ← This is important. )
8) Server: Here is another mirror.
9) Server: (Marks mirror server as 'possibly down' and checks connectivity again.)

As far as I understand your comment, apt cannot ask the server for a different mirror(?)

I guess in that case, this discussion would be better suited in the apt bugtracker, I guess.