add documentation how to access pull-through proxy stats
@@ -913,11 +913,17 @@ access to the debug endpoint is locked down in a production environment.
The `debug` section takes a single required `addr` parameter, which specifies
the `HOST:PORT` on which the debug server should accept connections.
+If the registry is configured as a pull-through cache, the `debug` server can be used
+to access proxy statistics. These statistics are exposed at `/debug/vars` in JSON format.
+
## `prometheus`
The `prometheus` option defines whether the prometheus metrics is enable, as well
as the path to access the metrics.
+>**NONE**: The prometheus metrics do **not** cover pull-through cache statistics.
+> Proxy statistics are exposed via `expvar` only.
+
| Parameter | Required | Description |
|-----------|----------|-------------------------------------------------------|
| `enabled` | no | Set `true` to enable the prometheus server |
