baudflow

Notifications

Alerts run through a four-layer pipeline, each layer one concern:

event → policy (notify?) → template (render) → channel (send)

NotificationWorker orchestrates it: it builds the event, asks the policy whether to notify, and only then loads the measurement and fans out. Adding a channel is one behaviour implementation and one Template.render/1 line, not a branch in the worker.

Events

Health transitions become typed events: :breach, :recovered, :failed (a test that errored), and :healthy. They’re constructed in exactly one place (HealthWorker) and carry a snapshot of the streak.

Policy

Policy.notify?/2 is pure. It reads only the event and a small config map, never the database. It’s what keeps alert fatigue down:

  • :breach fires exactly once, when the streak first reaches breach_notify_streak. A breach that climbs 1, 2, … N alerts only at N, never again, until it recovers and re-breaches. (Default breach_notify_streak is 1, so you alert on the first breach.)
  • :recovered and :failed fire on their transitions.
  • :healthy never fires.

Channels

Two ship out of the box.

ntfy

Posts to a self-hosted or hosted ntfy.sh topic. It’s wired through application env (deploy wiring, not a per-user setting):

config :baudflow,
  ntfy_url: "http://ntfy-svc",
  ntfy_topic: "baudflow"

Messages arrive with the title Baudflow Alert and priority high.

Webhook

POSTs a JSON payload to any URL: Home Assistant, Grafana, n8n, or a custom endpoint. Configure it on the Settings page:

  • webhook_url: the endpoint. Blank disables the channel (one “off” representation, no separate enable flag).
  • webhook_template: a custom JSON body (EEx). Blank means use the built-in default; a malformed template falls back to the default rather than crashing the queue.

A hung endpoint never holds a worker slot. Both channels post with hard connect and receive timeouts, and a failure is logged, never raised.

Adding a channel

Implement the Channel behaviour (send/1), add a Template.render(:your_channel) line to the fan-out, and a default template. Your channel owns its own transport config and enable gate; the worker never branches on it.