Noisebell

Door status monitor for Noisebridge. A Raspberry Pi watches a door sensor and reports open/closed state; remote services cache the data and fan it out to Discord and an Atom feed.

Architecture

Pi (door sensor) ──webhook──▸ Cache Service ──webhook──▸ Discord Bot
                                   │                        │
                        polls Pi ◂──┘            Atom feed ◂──┘
                                                  RSS Service

The Pi runs a small HTTP service that reads GPIO and exposes GET / (status) and GET /info. It also pushes state changes to the cache service via webhook.

The Cache Service is the central hub. It polls the Pi for status and info, stores everything in SQLite, and forwards state changes to downstream webhooks (Discord, etc.). It exposes a read API for consumers.

The Discord Bot receives webhooks from the cache service and posts embeds to a Discord channel.

The RSS Service fetches history from the cache service and serves an Atom feed of door events from the last 7 days.

Services

Service	Crate	Default Port	Description
Cache	noisebell-cache	3000	Polls Pi, caches state in SQLite, forwards webhooks
Discord	noisebell-discord	3001	Posts door status embeds to Discord
RSS	noisebell-rss	3002	Serves Atom feed of recent door events

Cache API

Method	Path	Auth	Description
GET	/status	None	Current door status (status, timestamp, last_seen)
GET	/info	None	Pi system info (JSON blob)
GET	/history	None	Last 100 state changes
POST	/webhook	Bearer token	Inbound webhook from Pi
GET	/health	None	Returns 200 OK

Building

All remote services live in a Cargo workspace under remote/.

cd remote
cargo build --release

Or with Nix:

cd remote
nix build .#noisebell-cache
nix build .#noisebell-discord
nix build .#noisebell-rss

NixOS Configuration

The flake at remote/flake.nix exports NixOS modules. Example configuration:

{
  inputs.noisebell.url = "git+https://git.extremist.software/jet/noisebell?dir=remote";

  outputs = { self, nixpkgs, noisebell, ... }: {
    nixosConfigurations.myhost = nixpkgs.lib.nixosSystem {
      system = "x86_64-linux";
      modules = [
        noisebell.nixosModules.default
        ({ ... }: {
          services.noisebell-cache = {
            enable = true;
            domain = "cache.noisebell.example.com";
            piAddress = "http://noisebell-pi:80";
            piApiKeyFile = "/run/secrets/noisebell-pi-api-key";
            inboundApiKeyFile = "/run/secrets/noisebell-inbound-api-key";
            outboundWebhooks = [
              {
                url = "http://localhost:3001/webhook";
                secretFile = "/run/secrets/noisebell-discord-webhook-secret";
              }
            ];
          };

          services.noisebell-discord = {
            enable = true;
            domain = "discord.noisebell.example.com";
            discordTokenFile = "/run/secrets/noisebell-discord-token";
            channelId = "123456789012345678";
            webhookSecretFile = "/run/secrets/noisebell-discord-webhook-secret";
          };

          services.noisebell-rss = {
            enable = true;
            domain = "rss.noisebell.example.com";
            cacheUrl = "http://localhost:3000";
          };
        })
      ];
    };
  };
}

Secrets

Secret	Used by	Description
piApiKeyFile	Cache	Bearer token for authenticating to Pi GET endpoints
inboundApiKeyFile	Cache	Bearer token the Pi uses when POSTing to /webhook
outboundWebhooks[].secretFile	Cache	Bearer token sent with outbound webhook POSTs
discordTokenFile	Discord	Discord bot token
webhookSecretFile	Discord	Must match the cache's outbound webhook secret