We want to have this in our own monitoring

refs privatestorageops#416, PrivateStorageio#115

Fixes #118

This reverts commit c8a13555.

Sadly, Borg says this is not a good idea: https://borgbackup.readthedocs.io/en/stable/faq.html#can-i-backup-from-multiple-servers-into-a-single-repository

Spoiler:  This won't work, Borg does not guarantee consistency with
parallel writers to the same repo as I now found out.

It's not really a key, and not really public, but not secret either.
This way, the tests can run.

Since that describes it better, especially now that I have
moved the one line that wasn't about the VPN out of it.

Tom Prince authored 3 years ago and Florian Sesser committed 3 years ago

This includes the host-based metrics collector, and the VPN client setup (including key deployment).

... and fix that option the other commit introduced

If I understand the behavior current Prometheus and Grafana
correctly, this should remove the port number from the
paymentserver labels in Prometheus TDSB.

Do some name resolution for those poor computers

Improve factoring by removing those `/etc/hosts` entries

And avoid the infinite loop @tomprince was encountering in !258

morph offers an auto-passed `nodes` parameter from which we can read all of
the nodes in the morph "network".  We can dig around in this to find the
monitoring node and then read its configured IP address.

It may be worth noting that this address appears in at least two places in the
configuration.  It appears in our "input" configuration which grid.nix
defines.  This change reads it from there.  We also have a NixOS module
`nixos/modules/monitoring/vpn/server.nix` which reads this "input" and uses it
to configure `networking.wireguard.interfaces.monitoringvpn`.  This is fed
onwards to <nixos> to generate actual system configuration.

It seems better to use the former than the latter because we have more direct
control over it and if we consider the whole configuration system a function
then it is more like an argument we are supplying rather than an obscure
implementation detail.

This reverts commit 3113a3e6.

Thinking a second time:  While the staging grid is deployed to
by an automaton anyway and it taking a minute longer won't bother
us, 20 % space savings is probably not worth slowing down
development interactivity.

This is the derivation I use when running `nix store diff-closures` for the
weekly nixpkgs update.

The derivation also includes some attributes that are useful for exploring the
various grid configurations in the nix repl.

Should be pure refactoring

This is my latest version of this, updated to work with the
packages in NixOS 21.05.