# Varnish Prometheus Business Exporter

Lightweight Python exporter for Varnish. It exposes `/metrics` for Prometheus and focuses on per-domain business/operational statistics rather than only raw counters.

## Requirements

- Python 3
- `varnishstat`
- `varnishlog`
- Access to Varnish shared memory/logs, usually by running as root or with proper permissions

No external Python dependencies are required.

## Quick start

Only varnishstat:

```bash
python3 varnish_exporter.py --modules core,stat
```

Test VSL without sampling:

```bash
sudo python3 varnish_exporter.py --enable-vsl --vsl-sample 1 --profile full
```

Recommended production mode:

```bash
sudo python3 varnish_exporter.py \
  --port 9131 \
  --enable-vsl \
  --profile standard \
  --vsl-sample 0.001
```

Then check:

```bash
curl -s http://127.0.0.1:9131/metrics | grep varnish_domain
```

## Profiles

- `minimal`: rps, hit ratio, backend ratio, 5xx ratio, p95 latency
- `standard`: recommended business-oriented domain statistics
- `full`: more detailed derived statistics
- `raw`: full plus raw HTTP counters/histograms

## Modules

- `core`: exporter self metrics
- `stat`: `varnishstat -1 -j`
- `vsl`: `varnishlog -g request`
- `domain`: derived per-domain statistics
- `raw`: raw request counters/histograms

Example:

```bash
sudo python3 varnish_exporter.py --modules core,stat,vsl,domain --profile standard
```

## Domain grouping

Use `config.example.json` as a template:

```bash
sudo python3 varnish_exporter.py \
  --config ./config.example.json \
  --enable-vsl \
  --profile standard
```

If no config is provided, the exporter uses the real Host header as the `site` label.

## Important notes

- Varnish cannot measure real browser render time such as LCP/FCP/DOMContentLoaded.
- Latency here means server-side response time as observed by Varnish.
- For high traffic, avoid `--vsl-sample 1` in production.
- Start production with `--vsl-sample 0.001` or `0.0001`.