# Alertmanager configuration

_Pointing Alertmanager at the server._ Back to the [README](../README.md) and the [documentation index](./README.md).

Alerts arrive on a team's **integration key**, which says both that the sender
may post and which team the alerts belong to. Mint one as an owner of the team:

```bash
curl -X POST https://terdut.example.com/api/teams/1/integrations \
  -H "Authorization: Bearer $TERDUT_API_KEY" \
  -H 'Content-Type: application/json' \
  -d '{"name":"prod alertmanager"}'
```

The response carries the key and the full URL **once**; only a SHA-256 hash is
stored. Put it in your `alertmanager.yml`:

```yaml
receivers:
  - name: terdut
    webhook_configs:
      - url: http://terdut-server:8080/api/integrations/<key>/alertmanager
        send_resolved: true

route:
  receiver: terdut
```

The whole URL is a credential, so treat it like one. Alertmanager 0.26 and
later can read it from a file with `url_file:` instead, which keeps it out of
your configuration repository:

```yaml
      - url_file: /etc/alertmanager/secrets/terdut-webhook-url/url
        send_resolved: true
```

The webhook endpoint requires no authentication.

If you use the [dead man's switch](./dead-mans-switch.md) — and the default configuration does — give
the heartbeat a route of its own, because the deadline is only as tight as the interval feeding it:

```yaml
route:
  receiver: terdut
  repeat_interval: 4h
  routes:
    - matchers: [ 'alertname = "Watchdog"' ]
      receiver: terdut
      group_wait: 0s
      group_interval: 1m
      repeat_interval: 1m
```

That delivers a heartbeat every **2 minutes**, not every minute. Alertmanager only reconsiders a
group every `group_interval`, and at exactly one elapsed interval `repeat_interval` has not *quite*
passed, so the send slips to the next tick — equal values give 2×. Two minutes against the 15 minute
default is seven heartbeats per window, which is the point; use `group_interval: 30s` if you want
the numbers to mean what they say.

kube-prometheus-stack users get the `Watchdog` alert (`expr: vector(1)`) for free; it just needs
routing to terdut rather than to `null`.