NixOS Buildermon

Single-binary monitor for NixOS builders. See what your nixos buiilders are building, by simply visiting their url.

It provides:

• live build output from /var/log/nom-output.log via SSE
• sysinfo-only system metrics (CPU, RAM, swap, disks, network)
• SSE fan-out with server-side cached snapshots
• browser-tab aware update coordination to reduce duplicate refresh work

Warning

Build logs are exposed as-is via HTTP -- no auth or encryption. This is fine for my risk appetite on a local network with low-stakes packages, it may not be for yours!

Highlights

• Modern light/dark theme
• Uses sysinfo exclusively for system metrics
• Forwards nix-daemon logs through nix-output-monitor (nom)
• Preserves ANSI output and renders it in the web terminal
• Includes per-core and network data

Recommended Build Commands

For best NOM detail, run builds through nom directly:

nom build .#your-target

This follows the NOM "easy way" (nom build) and keeps NOM as the primary parser/output layer.

If you need a manual JSON pipeline, use:

nix build .#your-target --log-format internal-json -v |& nom --json

NixOS Integration

In your system flake (Git input example):

{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    nixos-buildermon.url = "github:balaclava-guy/nixos-buildermon";
    nixos-buildermon.inputs.nixpkgs.follows = "nixpkgs";
  };

  outputs = { self, nixpkgs, nixos-buildermon, ... }: {
    nixosConfigurations.builder = nixpkgs.lib.nixosSystem {
      system = "x86_64-linux";
      modules = [
        ./configuration.nix
        nixos-buildermon.nixosModules.default
        {
          services.nixos-buildermon = {
            enable = true;
            port = 8091;
            openFirewall = true;
          };
        }
      ];
    };
  };
}

Then apply it:

sudo nixos-rebuild switch --flake .#builder

The module configures:

• nixos-buildermon service (web UI)
• nixos-buildermon-daemon service (journalctl nix-daemon | nom | tee /var/log/nom-output.log)
• Nerd fonts (JetBrains Mono Nerd Font, Iosevka Nerd Font)
• nix-output-monitor package on system

Useful checks:

systemctl status nixos-buildermon
systemctl status nixos-buildermon-daemon
journalctl -u nixos-buildermon -f
journalctl -u nixos-buildermon-daemon -f

Development

Use Dioxus commands through Nix:

nix run .#dx-serve -- --port 8091
nix run .#dx-build

Or from the dev shell:

nix develop -c dx serve --port 8091
nix develop -c dx build --platform web --release --fullstack true --features web
nix develop -c cargo check --features server
nix develop -c cargo check --no-default-features --features web --target wasm32-unknown-unknown

Architecture

• src/main.rs: Dioxus app, server functions, and server-side metrics collector
• assets/style.css: UI styles, terminal/Nerd Font stack, responsive layout
• flake.nix: package + NixOS module wiring

Notes on Resource Use

• metrics are collected in a single shared background task
• server exposes SSE streams for metrics and build logs
• background/hidden tabs pause active stream ownership; a visible tab renews ownership
• server functions still return cached snapshots for fallback reads
• CPU refresh follows sysinfo delta semantics (MINIMUM_CPU_UPDATE_INTERVAL warmup)
• disk list refresh is throttled

License

MIT