2024-09-05 08:50:47 +02:00
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SPDX-FileCopyrightText: 2023-2024 Christina Sørensen
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SPDX-FileContributor: Christina Sørensen
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SPDX-License-Identifier: EUPL-1.2
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-->
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<div align="center">
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# Weather - Check Cache Availablility of NixOS Configurations
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A *fast* rust tool to check availability of your entire system in caches. It so
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to speak "checks the weather" before going to update. Heavily inspired by [`guix
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weather`](https://guix.gnu.org/manual/en/html_node/Invoking-guix-weather.html).
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[](https://nixos.org)
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[](CODE_OF_CONDUCT.md)
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[](https://api.reuse.software/info/git.fsfe.org/reuse/api)
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[](https://commission.europa.eu/content/european-union-public-licence_en)
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</div>
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2024-09-05 09:39:42 +02:00
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## How It Works
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The basic idea is that we construct a set of all requisites to build the
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top-level of a NixOS configuration, and then query Nix cache(s) for the narinfo.
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By doing this in a high concurrency, parallel task runner (i.e. tokio async
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runtime), and only querying the headers for status codes, we can reach
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impressive speeds, typically around 45~ network time.
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One of the biggest limiting factors regarding speed is building the
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`config.system.toplevel`, and finding the necessary requisites with `nix-store`.
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Caching the requisites is a future goal, so that we only have to build the
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`toplevel`, and then match against its derivation in cache, which should cut
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down the nix part of the runtime by ~80%.
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## Usage
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> **Note**
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> Currently, `nix-weather` only has first-class support for flakes.
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General usage would be like this:
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```bash
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nix-weather --name myhost --config ~/git/my-nixos-config
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```
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Here, we specify the name of the host, as specified at the flake output
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`nixosConfiguration`, and a path to the NixOS configuration flake.
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