terdut-server/README.md

# Terminal Duty (terdut-server)

Incident management server for teams using Prometheus Alertmanager.

- Receives Alertmanager webhooks directly — no adapter needed
- Turns alerts into **incidents**, correlated by Alertmanager's own `groupKey`
- Incident workflow: acknowledge, assign, snooze, note, resolve, with a full timeline
- On-call schedule management, with new incidents auto-assigned to whoever is on call
- Alert and incident statistics, including MTTA and MTTR
- REST API with per-user API key authentication
- Single binary, SQLite storage — trivial to self-host

---

## Quick start

**Prerequisites:** Go 1.21+

```bash
git clone https://github.com/yeniklas/terdut-server
cd terdut-server
go run ./cmd/terdut
```

The server starts on `:8080` with a `terdut.db` file in the working directory.

### Create the first user

```bash
curl -X POST http://localhost:8080/api/bootstrap \
  -H "Content-Type: application/json" \
  -d '{"username": "admin", "email": "admin@example.com"}'
```

Save the `api_key.key` value from the response — it is shown **once only**.

Use it as a bearer token for all subsequent requests:

```bash
export KEY=<your-key>
curl -H "Authorization: Bearer $KEY" http://localhost:8080/api/users
```

### Docker

```bash
docker build -t terdut-server .
docker run -p 8080:8080 -v $(pwd)/data:/data \
  -e TERDUT_DB_PATH=/data/terdut.db \
  terdut-server
```

---

## Configuration

| Variable | Default | Description |
|---|---|---|
| `TERDUT_ADDR` | `:8080` | TCP address to listen on |
| `TERDUT_DB_PATH` | `terdut.db` | Path to the SQLite database file |
| `TERDUT_ARCHIVE_AFTER` | `168h` (7d) | How long a resolved alert or incident stays in the default list before being auto-archived |
| `TERDUT_STALE_AFTER` | `6h` | How long a firing alert may go without a refreshing webhook before it is treated as resolved — **must exceed your Alertmanager `repeat_interval`** |

Durations use Go syntax (`30m`, `12h`, `168h`). An unparseable value falls back to the default.

In the Helm chart the two sweeper durations are set via `sweeper.staleAfter` and `sweeper.archiveAfter`.

---

## Alertmanager configuration

Add terdut-server as a webhook receiver in your `alertmanager.yml`:

```yaml
receivers:
  - name: terdut
    webhook_configs:
      - url: http://terdut-server:8080/api/alertmanager/webhook
        send_resolved: true

route:
  receiver: terdut
```

The webhook endpoint requires no authentication.

---

## Alerts and incidents

There are two objects, and the difference between them is the whole design.

**An alert is Alertmanager's record.** It has two states, `firing` and
`resolved`, one row per fingerprint, and no human ever writes to it. The API
exposes alerts read-only.

**An incident is the work item.** It goes `triggered → acknowledged → resolved`,
carries an assignee, a snooze, notes and a timeline, and is the only thing people
act on. Many alerts belong to one incident.

### Correlation uses Alertmanager's `groupKey`

Alertmanager has already grouped alerts according to the `group_by` routing tree
you configured, and it sends the resulting `groupKey` and `groupLabels` on every
webhook. Incidents adopt that answer rather than re-grouping alerts a second
time — if you want different correlation, change `group_by` in
`alertmanager.yml` and terdut follows.

At most one incident is open per `groupKey` at a time. Alerts firing in a group
that already has an open incident join it. The incident's `severity` is a
high-water mark — the highest `severity` label any of its alerts has carried — so
an incident that hit `critical` still reads as critical after the critical alert
clears.

### An incident opens only on a new occurrence

An incident opens when an alert **transitions into firing**: a fingerprint that
was never seen, an alert with a newer `startsAt`, or a resolved alert that
started again. The unchanged firing notifications Alertmanager re-sends every
`repeat_interval` are none of those, and open nothing.

This is what makes closing an incident by hand mean something. Without the rule,
`POST /api/incidents/{id}/resolve` would be undone by the next re-send of an
alert that never stopped firing.

### Leaving the open state

- **Automatically**, once every alert under the incident has stopped firing —
  whether by a resolved webhook or by the sweeper's
  [stale-alert expiry](#stale-alert-expiry). The incident gets
  `"resolution_source": "alerts"`.
- **By hand**, via `POST /api/incidents/{id}/resolve`
  (`"resolution_source": "manual"`). This is **terminal**: a later occurrence in
  that group opens a *new* incident rather than reopening this one. If the alert
  underneath never stops firing, the incident stays closed — that is what
  resolving by hand asserts.

To quieten an incident you expect to come back, snooze it instead
(`POST /api/incidents/{id}/snooze`). A snooze hides the incident from the default
list without closing it, and expires by simply falling into the past.

### On-call assignment

A new incident is assigned to whoever holds today's schedule entry at the moment
it opens (`GET /api/schedule/current`). If nobody is scheduled it opens
unassigned. Reassign with `POST /api/incidents/{id}/assign`.

### Stale alert expiry

A resolved webhook is the only signal that an alert has stopped firing, so a
notification that is dropped, silenced, or lost to a restart would otherwise pin
that alert as firing forever. A background sweeper resolves firing alerts that
Alertmanager has stopped refreshing, using either signal:

- the `endsAt` watermark on the last notification has passed, or
- no webhook has refreshed the alert within `TERDUT_STALE_AFTER`.

Alertmanager re-sends firing notifications every `repeat_interval`, which is what
keeps a live alert fresh — so `TERDUT_STALE_AFTER` must be comfortably larger
than your `repeat_interval` (default 4h), or live alerts will be resolved
prematurely. Alerts resolved this way are marked `"resolution_source": "expiry"`
to distinguish them from a real Alertmanager resolve (`"alertmanager"`).

An expiry cascades: once it leaves an incident with nothing firing under it, the
incident resolves too, in the same sweep.

---

## API reference

### Authentication

All endpoints except `/api/bootstrap` and `/api/alertmanager/webhook` require:

```
Authorization: Bearer <api-key>
```

### Users

| Method | Path | Description |
|---|---|---|
| `POST` | `/api/bootstrap` | Create first user + API key (only works on empty DB) |
| `GET` | `/api/users` | List users |
| `POST` | `/api/users` | Create user `{"username","email"}` |
| `DELETE` | `/api/users/{id}` | Delete user (cascades to keys) |
| `POST` | `/api/users/{id}/api-keys` | Issue API key `{"name"}` — key shown once |
| `DELETE` | `/api/users/{id}/api-keys/{keyID}` | Revoke API key |

### Alert ingestion

| Method | Path | Description |
|---|---|---|
| `POST` | `/api/alertmanager/webhook` | Alertmanager v4 webhook receiver (no auth) |

### Incidents

| Method | Path | Description |
|---|---|---|
| `GET` | `/api/incidents` | List incidents. Filters: `?status=triggered\|acknowledged\|resolved`, `?severity=`, `?assigned_to=<user id>`, `?archived=true`, `?snoozed=true`, `?from=YYYY-MM-DD`, `?to=YYYY-MM-DD`, `?sort=severity`, `?limit=` (default 50, max 500) |
| `GET` | `/api/incidents/{id}` | Get single incident, with its alerts inline |
| `GET` | `/api/incidents/{id}/alerts` | Alerts under this incident |
| `GET` | `/api/incidents/{id}/timeline` | Full event history, chronological |
| `POST` | `/api/incidents/{id}/acknowledge` | Acknowledge (stamps authed user + time) |
| `DELETE` | `/api/incidents/{id}/acknowledge` | Clear acknowledgement, back to `triggered` |
| `POST` | `/api/incidents/{id}/resolve` | Close by hand — **terminal**, see above |
| `POST` | `/api/incidents/{id}/assign` | Reassign `{"user_id"}` |
| `POST` | `/api/incidents/{id}/snooze` | Hide until `{"until": RFC3339}` or `{"duration": "2h"}` |
| `DELETE` | `/api/incidents/{id}/snooze` | Un-snooze |
| `POST` | `/api/incidents/{id}/archive` | Archive (hides from the default list) |
| `DELETE` | `/api/incidents/{id}/archive` | Un-archive |
| `POST` | `/api/incidents/{id}/notes` | Add a note `{"content"}` |
| `DELETE` | `/api/incidents/{id}/notes/{eventID}` | Delete own note |

With no `?status=` filter, `GET /api/incidents` returns **open** incidents only —
the queue an on-call person wants. Currently snoozed and archived incidents are
excluded unless asked for. Actions that only make sense on an open incident
return `409` once it is resolved.

Notes are ordinary timeline events of type `note`; only they are deletable, and
only by their author. The rest of the timeline is a record of what happened.

#### The incident object

| Field | Type | Notes |
|---|---|---|
| `id` | integer | Server-assigned |
| `group_key` | string | Alertmanager's `groupKey` — opaque, treat as an identifier |
| `title` | string | Rendered from `groupLabels` |
| `group_labels` | object | String→string, as sent by Alertmanager |
| `status` | string | `"triggered"`, `"acknowledged"` or `"resolved"` |
| `severity` | string | *optional* — high-water mark across the incident's alerts; never lowered |
| `triggered_at` | timestamp | When the incident opened |
| `acknowledged_by_id` / `acknowledged_by` / `acknowledged_at` | | *optional* — user id, username, time |
| `assigned_to_id` / `assigned_to` | | *optional* — user id, username |
| `snoozed_until` | timestamp | *optional* — a value in the past reads as not snoozed |
| `resolved_at` | timestamp | *optional* |
| `resolution_source` | string | *optional* — `"alerts"` or `"manual"` |
| `archived_at` | timestamp | *optional* |
| `alerts` | array | Only on `GET /api/incidents/{id}` |

Treat `resolution_source` as an open set, as with the alert field of the same
name: degrade unknown values to "resolved, reason unknown".

#### The timeline event object

| Field | Type | Notes |
|---|---|---|
| `id` | integer | |
| `incident_id` | integer | |
| `type` | string | See below — treat as an open set |
| `user_id` / `username` | | *optional* — absent when the server acted rather than a person |
| `alert_id` | integer | *optional* — the alert an `alert_added` / `alert_resolved` event refers to |
| `detail` | string | *optional* — the note body, the snooze deadline, etc. |
| `created_at` | timestamp | |

Types written today: `triggered`, `alert_added`, `alert_resolved`,
`acknowledged`, `unacknowledged`, `assigned`, `snoozed`, `unsnoozed`, `resolved`,
`note`. On an `assigned` event `user_id` is the **assignee**, not the actor. New
types may be added; render unknown ones generically rather than dropping them.

### Alerts

Alerts are read-only. Everything a person does happens on the incident.

| Method | Path | Description |
|---|---|---|
| `GET` | `/api/alerts` | List alerts. Filters: `?status=firing\|resolved`, `?name=`, `?incident_id=`, `?archived=true`, `?from=YYYY-MM-DD`, `?to=YYYY-MM-DD`, `?limit=` (default 50, max 500) |
| `GET` | `/api/alerts/{id}` | Get single alert |

Archived alerts are hidden from `GET /api/alerts` unless `?archived=true` is
passed; alert archiving is automatic housekeeping by the sweeper, not a user
action. Resolved alerts carry `resolution_source`: `"alertmanager"` for a real
resolved webhook, `"expiry"` when the sweeper inferred it (see
[Stale alert expiry](#stale-alert-expiry)).

#### The alert object

Returned by `GET /api/alerts` (as an array) and `GET /api/alerts/{id}`.
Timestamps are RFC 3339 in UTC. Fields marked *optional* are omitted entirely
when unset, so clients must treat them as nullable.

| Field | Type | Notes |
|---|---|---|
| `id` | integer | Server-assigned; stable for the life of the row |
| `fingerprint` | string | Alertmanager's fingerprint — the upsert key |
| `name` | string | From the `alertname` label |
| `status` | string | `"firing"` or `"resolved"` |
| `labels` | object | String→string, as sent by Alertmanager |
| `annotations` | object | String→string, as sent by Alertmanager |
| `starts_at` | timestamp | When the alert instance began, **per Prometheus** |
| `ends_at` | timestamp | *optional* — absent while no end is known |
| `generator_url` | string | Link back to the originating Prometheus |
| `received_at` | timestamp | When the server last accepted a webhook for this alert — see below |
| `incident_id` | integer | *optional* — the most recent incident this alert belongs to |
| `resolution_source` | string | *optional* — `"alertmanager"` or `"expiry"` |
| `archived_at` | timestamp | *optional* — set while archived |

##### `received_at` is a liveness heartbeat

`starts_at` comes from Prometheus and **never changes** for the lifetime of an
alert instance. It says when the problem began, not whether it is still
happening — an alert that started twelve days ago looks identical whether
Alertmanager refreshed it a minute ago or went silent a week ago.

`received_at` is the field that answers "is this still live". It is set to the
server's clock on **every accepted webhook** for that fingerprint, including the
unchanged firing notifications Alertmanager re-sends every `repeat_interval`.
Clients may rely on this:

- **A firing alert whose `received_at` is advancing is still being refreshed.**
  Stale-dating it against `repeat_interval` is a valid liveness check, and it is
  what the built-in sweeper does (see
  [Stale alert expiry](#stale-alert-expiry)).
- **`received_at` tracks accepted payloads, not delivery attempts.** A retry
  that describes an older instance than the stored one is discarded, and a
  discarded payload does not move `received_at`.
- **It stops advancing once the alert resolves,** because Alertmanager stops
  re-sending. On an alert resolved by the sweeper
  (`"resolution_source": "expiry"`) it therefore marks the last time
  Alertmanager was actually heard from, which is earlier than `ends_at`.

`GET /api/alerts` is ordered by `received_at` descending — most recently
refreshed first — and the `?from=` / `?to=` filters on both the alert and stats
endpoints select on `received_at`, not `starts_at`.

##### `resolution_source` says how much to trust `ends_at`

An alert can leave the firing state two ways, and `resolution_source` records
which happened. Clients may rely on this:

- **Absent while firing.** It is set only on resolve, and a re-fire under the
  same fingerprint clears it again, so its presence always agrees with
  `"status": "resolved"`.
- **`"alertmanager"` — a real resolved webhook arrived.** `ends_at` is the end
  time Alertmanager reported. It is an observed value and can be displayed as
  fact.
- **`"expiry"` — the sweeper inferred the resolve** because Alertmanager stopped
  refreshing the alert (see [Stale alert expiry](#stale-alert-expiry)). Nothing
  ever reported an end, so **`ends_at` is approximate**: it is either the stale
  `endsAt` watermark from the last notification, or — when that notification
  carried none — the time the sweep ran, which lags the last real contact by up
  to `TERDUT_STALE_AFTER` plus a sweep interval. Treat it as "no later than",
  not as when the problem stopped.

  On these alerts `received_at` is the more truthful signal: it marks the last
  time Alertmanager was actually heard from. Surfacing the distinction is
  worthwhile, since `"expiry"` can also mean the alert is still firing and the
  notification path broke.

Treat the value as an open set and tolerate ones you do not recognise — new
sources may be added, and unknown values should degrade to "resolved, reason
unknown" rather than being rejected.

### On-call schedule

| Method | Path | Description |
|---|---|---|
| `POST` | `/api/schedule` | Assign user to dates `{"user_id", "dates":["YYYY-MM-DD",...]}` — all-or-nothing |
| `GET` | `/api/schedule` | List entries. Filters: `?from=YYYY-MM-DD`, `?to=YYYY-MM-DD` |
| `GET` | `/api/schedule/current` | Today's on-call user (UTC), 404 if none |
| `DELETE` | `/api/schedule/{id}` | Remove schedule entry |

### Statistics

All stat endpoints accept optional `?from=YYYY-MM-DD` and `?to=YYYY-MM-DD`, and exclude archived rows to match the default list views. Alert stats filter on `received_at`; incident stats filter on `triggered_at`.

| Method | Path | Description |
|---|---|---|
| `GET` | `/api/stats/incidents` | `{total, triggered, acknowledged, resolved, mtta_seconds, mttr_seconds}` |
| `GET` | `/api/stats/alerts` | `{total, firing, resolved}` counts |
| `GET` | `/api/stats/alerts/top` | Most frequent alert names. `?limit=` (default 10, max 100) |
| `GET` | `/api/stats/alerts/by-hour` | Count per hour-of-day (UTC), all 24 slots returned |
| `GET` | `/api/stats/alerts/by-day` | Count per day-of-week, all 7 slots with names returned |

`mtta_seconds` (time to acknowledge) and `mttr_seconds` (time to resolve) are
averages over incidents that have actually been acknowledged or resolved, and are
**null** until there are any — null means "no data", not zero.

---

## Upgrading to incidents

The incidents release moves the workflow off alerts, which is a **breaking API
change**. These endpoints are gone:

| Removed | Replacement |
|---|---|
| `POST`/`DELETE` `/api/alerts/{id}/acknowledge` | `POST`/`DELETE` `/api/incidents/{id}/acknowledge` |
| `POST`/`DELETE` `/api/alerts/{id}/archive` | `POST`/`DELETE` `/api/incidents/{id}/archive` (alert archiving is now sweeper-only) |
| `GET`/`POST` `/api/alerts/{id}/comments` | `GET /api/incidents/{id}/timeline`, `POST /api/incidents/{id}/notes` |
| `DELETE /api/alerts/{id}/comments/{commentID}` | `DELETE /api/incidents/{id}/notes/{eventID}` |

The alert object also drops `acknowledged_by_id`, `acknowledged_by` and
`acknowledged_at`, and gains `incident_id`.

Migration `008_incidents.sql` runs automatically on start and preserves existing
data: every alert gets a backfilled incident carrying its acknowledgement, and
comments become timeline notes. Backfilled incidents have a `group_key` of
`backfill:<fingerprint>` — there is no historical `groupKey` to correlate on, so
they are one-per-alert rather than grouped.

Nothing about the two documented alert contracts changes: `received_at` is still
advanced on every accepted webhook, and `resolution_source` still means what it
did.

---

## Development

```bash
go test ./...        # run all tests
go build ./...       # compile all packages
go run ./cmd/terdut  # run locally
```