Note Currently, nix-weather only has first-class support for flakes.

General usage would be like this:

nix-weather --name myhost --config ~/git/my-nixos-config

Here, we specify the name of the host, as specified at the flake output nixosConfiguration, and a path to the NixOS configuration flake.

The basic idea is that we construct a set of all requisites to build the top-level of a NixOS configuration, and then query Nix cache(s) for the narinfo. By doing this in a high concurrency, parallel task runner (i.e. tokio async runtime), and only querying the headers for status codes, we can reach impressive speeds, typically around 45~ network time.

One of the biggest limiting factors regarding speed is building the config.system.toplevel, and finding the necessary requisites with nix-store. Caching the requisites is a future goal, so that we only have to build the toplevel, and then match against its derivation in cache, which should cut down the nix part of the runtime by ~80%.