noisebell/remote/cache-service

Cache Service

The central hub. Sits between the Pi and Discord.

It does two things: polls the Pi on a timer to keep a local copy of the door state, and receives push webhooks from the Pi when the state actually changes. Either way, updates get written to SQLite and forwarded to downstream services via outbound webhooks.

If the Pi stops responding to polls (configurable threshold, default 3 misses), the cache marks it as offline and notifies downstream.

API

Method	Path	Auth	Description
GET	/status	—	Current door status (status, since, last_checked)
GET	/badge.svg	—	Live README badge with Noisebridge logo
GET	/metrics	—	Prometheus metrics, scraped locally by the DO Prometheus
POST	/webhook	Bearer	Inbound webhook from the Pi
GET	/health	—	Health check

since is the Pi-reported time when the current state began. last_checked is when the cache most recently attempted a poll.

The public Caddy vhost returns 404 for /metrics; Prometheus scrapes the cache directly on localhost. Metrics include the configured Pi target, poll interval, offline threshold, last poll result, last HTTP status, last poll duration, last poll attempt/success/failure timestamps, and failure counters split into HTTP, timeout, connect, request-other, and parse failures.

Regular timer-driven poll data should be debugged from Prometheus and Grafana, not by scanning logs. The cache logs sparse events instead: state changes applied from the Pi, offline/online transitions, first or changed poll failures in a failure streak, stale events, auth/rate-limit rejections, outbound webhook deliveries, retries, and final failures. Successful unchanged polls, badge/image/status reads, and metrics scrapes are intentionally quiet at INFO.

Badge

/badge.svg serves a classic shields.io-style SVG badge with the Noisebridge logo and the current cache status (open, closed, or offline).

Use it in a GitHub README like this:

[![Space status](https://your-cache-domain.example.com/badge.svg)](https://your-cache-domain.example.com/status)

That keeps the badge clickable and sends readers to the live /status endpoint.

Configuration

NixOS options under services.noisebell-cache:

Option	Default	Description
domain	required	Caddy virtual host domain
piAddress	required	Pi URL (e.g. http://noisebell:80)
piApiKeyFile	required	Key file for authenticating to the Pi
inboundApiKeyFile	required	Key file for validating inbound webhooks
port	3000	Listen port
statusPollIntervalSecs	60	How often to poll GET / on the Pi
offlineThreshold	3	Consecutive failed polls before marking offline
retryAttempts	3	Outbound webhook retry count
retryBaseDelaySecs	1	Exponential backoff base delay
httpTimeoutSecs	10	HTTP request timeout
dataDir	/var/lib/noisebell-cache	SQLite database location
outboundWebhooks	[]	List of {url, secretFile} for downstream services

Secrets

Secret	What it's for
piApiKeyFile	Bearer token to poll the Pi's GET endpoints
inboundApiKeyFile	Bearer token the Pi sends when POSTing to /webhook
outboundWebhooks[].secretFile	Bearer token sent with outbound webhook POSTs

Home Assistant

Home Assistant works well as another outboundWebhooks target.

• For fast automations, point a webhook target at Home Assistant's /api/webhook/<webhook_id> endpoint.
• For current-state display and restart recovery, have Home Assistant also poll GET /status.

Example NixOS config:

{
  services.noisebell-cache.outboundWebhooks = [
    {
      url = "https://homeassistant.example.com/api/webhook/noisebell-door";
      secretFile = null;
    }
  ];
}

The webhook payload sent by cache-service is:

{
  "status": "open",
  "timestamp": 1710000000
}

secretFile = null is usually fine for Home Assistant webhook triggers because the webhook ID itself acts as the secret. If you place Home Assistant behind an extra auth layer that expects a bearer token, set secretFile to a file containing that token.