# Traefik Plugin

The Traefik plugin scrapes the Traefik reverse proxy's Prometheus `/metrics` endpoint on a configurable interval, stores per-router metrics, and surfaces them on the dashboard and a dedicated detail page.

---

## What It Does

On each scrape:
1. Fetches raw Prometheus text from the configured `metrics_url`
2. Parses histogram and counter data to compute per-router rates and latency approximations
3. Writes computed metrics to the `traefik_metrics` history table
4. Calls `record_metric()` for each metric, making them available to alert rules

Request rates and error rates are computed as deltas between the current and previous scrape, divided by elapsed time. Latency percentiles (p50, p95, p99) are approximated via linear interpolation over histogram buckets — these are estimates, not exact percentiles. They cover the responses since the previous scrape (each bucket's rise, summed over every status code and method), not every response since Traefik started. A scrape in which a router answered nothing records no latency, shown as "—"; one past the last bucket (5 s by default) reads as that bucket's edge.

---

## Configuration

| Key | Default | Description |
|---|---|---|
| `metrics_url` | `http://localhost:8080/metrics` | Traefik Prometheus endpoint |
| `scrape_interval_seconds` | `60` | How often to scrape |

Enable the plugin by setting `enabled: true` in the app settings (Settings UI or directly in `app_settings` DB table under key `plugin.traefik`).

Traefik must have metrics enabled. In Traefik config:

```yaml
# traefik.yml
metrics:
  prometheus: {}
```

---

## Metrics Collected

Per Traefik router, per scrape:

| Metric name | Description |
|---|---|
| `request_rate` | Requests per second (delta from previous scrape) |
| `error_rate_4xx_pct` | 4xx responses as % of total requests |
| `error_rate_5xx_pct` | 5xx responses as % of total requests |
| `latency_p50_ms` | Approximate p50 latency (ms) |
| `latency_p95_ms` | Approximate p95 latency (ms) |
| `latency_p99_ms` | Approximate p99 latency (ms) |

All metrics are available for alert rules with `source_module = "traefik"` and `resource_name = <router name>`.

---

## Alert Rule Examples

| Rule | source_module | resource_name | metric_name | operator | threshold |
|---|---|---|---|---|---|
| High 5xx rate on API router | `traefik` | `api@docker` | `error_rate_5xx_pct` | `>` | `1.0` |
| Slow API (p95 > 500ms) | `traefik` | `api@docker` | `latency_p95_ms` | `>` | `500` |
| Traffic spike | `traefik` | `web@docker` | `request_rate` | `>` | `1000` |

Router names are the Traefik router labels as reported in the Prometheus metrics (e.g. `api@docker`, `dashboard@internal`). Check the raw metrics at your `metrics_url` to see the exact names in use.

---

## UI

### Dashboard Widget

The widget appears on the dashboard when the Traefik plugin is enabled. It shows, per router:

- Router name
- Current req/s
- p95 latency (color-coded: green < 200ms, yellow < 500ms, red ≥ 500ms)
- 5xx error rate (shown only if > 0)

The widget auto-refreshes via HTMX polling every `poll_interval` seconds. Fragment endpoint: `GET /plugins/traefik/widget`.

### Detail Page

The full Traefik page at `/plugins/traefik/` reads top to bottom, for the time range picked at the top:

1. **The verdict.** It names the routers that need a look, says why, and says when the problem started ("api, 3.0% of responses are 5xx, started 2h ago"). When a router has been a problem for the whole range, it says so instead. Otherwise it reads "All N routers healthy".
2. **The request chart.** Requests per second across all routers and the share answered 5xx, the same chart as the dashboard widget.
3. **A card for each router that needs a look:** why, since when, the 4xx and 5xx status codes it answered in the last 15 minutes, most first ("404 ×1,812, 502 ×40"), and its request rate, bandwidth, p95/p99 latency and 4xx/5xx shares, each with its history. The code is what separates scanners probing for pages (404), a login wall (401/403) and an app that isn't answering (502/503/504). Steward records codes from the version that added them on; until then a card says they aren't recorded yet.
4. **Traefik's own figures:** when its config last reloaded, open connections, memory.
5. **The healthy routers,** folded into one table, then the routers Traefik no longer reports, then TLS certificates by soonest expiry, then Traffic Origin when the access log is on.

A router is graded on its last 15 minutes against Settings → Thresholds. When a problem started is read from the router's history over the range.

---

## File Locations

| File | Purpose |
|---|---|
| `plugins/traefik/__init__.py` | Plugin entry point: `setup()`, `get_scheduled_tasks()`, `get_blueprint()` |
| `plugins/traefik/plugin.yaml` | Plugin metadata and default config |
| `plugins/traefik/models.py` | `TraefikMetric` SQLAlchemy model |
| `plugins/traefik/scheduler.py` | `make_scrape_task()` and scrape logic |
| `plugins/traefik/scraper.py` | Prometheus text parsing and metric computation |
| `plugins/traefik/routes.py` | `GET /` (detail page) and `GET /widget` (HTMX fragment) |
| `plugins/traefik/migrations/` | Alembic migration for `traefik_metrics` table |
| `plugins/traefik/templates/traefik/` | `index.html` (detail) and `widget.html` (dashboard fragment) |

---

## Database Table

`traefik_metrics` (defined in `plugins/traefik/models.py`):

| Column | Type | Description |
|---|---|---|
| `id` | UUID | Primary key |
| `router_name` | str | Traefik router name |
| `scraped_at` | timestamp UTC | When this row was written |
| `request_rate` | float | req/s |
| `error_rate_4xx_pct` | float | % 4xx |
| `error_rate_5xx_pct` | float | % 5xx |
| `latency_p50_ms` | float | Approx p50 (ms) |
| `latency_p95_ms` | float | Approx p95 (ms) |
| `latency_p99_ms` | float | Approx p99 (ms) |