Add beta metrics documentation

CHANGELOG.md

@@ -25,6 +25,7 @@ Unreleased changes are available as `avenga/couper:edge` container.
 * [**Beta**](./docs/BETA.md)
   * `beta_scope_claim` attribute to [`jwt` block](./docs/REFERENCE.md#jwt-block); `beta_scope` attribute to [`api`](./docs/REFERENCE.md#api-block) and [`endpoint` block](./docs/REFERENCE.md#endpoint-block)s; [error types](./docs/ERRORS.md#error-types) `beta_operation_denied` and `beta_insufficient_scope` ([#315](https://github.com/avenga/couper/pull/315))
   * `beta_roles_claim` and `beta_roles_map` attributes to [`jwt` block](./docs/REFERENCE.md#jwt-block) ([#325](https://github.com/avenga/couper/pull/325)) ([#338](https://github.com/avenga/couper/pull/338)) ([#352](https://github.com/avenga/couper/pull/352))
+  * Metrics: [Prometheus exporter](./docs/METRICS.md) ([#295](https://github.com/avenga/couper/pull/295))
 
 * **Dependencies**
   * build with go 1.17 ([#331](https://github.com/avenga/couper/pull/331))

DOCKER.md

@@ -44,6 +44,10 @@ docker run avenga/couper run -watch -p 8081
 | COUPER_WATCH_RETRY_DELAY             | `500ms` | Delay duration before next attempt if an error occurs. |
 | COUPER_XFH                           | `false` | Global configurations which uses the `Forwarded-Host` header instead of the request host. |
 |                                      | | |
+| COUPER_BETA_METRICS                  | `false`  | Option to enable the prometheus [metrics](https://github.com/avenga/couper/blob/master/docs/METRICS.md) exporter. |
+| COUPER_BETA_METRICS_PORT             | `9090`   | Prometheus exporter listen port. |
+| COUPER_BETA_SERVICE_NAME             | `couper` | The service name which applies to the `service_name` metric labels. |
+|                                      | | |
 | COUPER_REQUEST_ID_ACCEPT_FROM_HEADER | `""` | Name of a client request HTTP header field that transports the `request.id` which Couper takes for logging and transport to the backend (if configured). |
 | COUPER_REQUEST_ID_BACKEND_HEADER     | `Couper-Request-ID` | Name of a HTTP header field which Couper uses to transport the `request.id` to the backend. |
 | COUPER_REQUEST_ID_CLIENT_HEADER      | `Couper-Request-ID` | Name of a HTTP header field which Couper uses to transport the `request.id` to the client. |

docs/CLI.md

@@ -33,3 +33,6 @@ _Note_: `log-format`, `log-level` and `log-pretty` also map to [settings](REFERE
 | :---------------------- | :----------- | :---------------------------- | :----------- |
 | `-accept-forwarded-url` | empty string | `COUPER_ACCEPT_FORWARDED_URL` | Which `X-Forwarded-*` request headers should be accepted to change the [request variables](./REFERENCE.md#request) `url`, `origin`, `protocol`, `host`, `port`. Comma-separated list of values. Valid values: `proto`, `host`, `port` |
 | `-https-dev-proxy`      | empty string | `COUPER_HTTPS_DEV_PROXY`      | List of tls port mappings to define the tls listen port and the target one. A self-signed certificate will be generated on the fly based on given hostname. |
+| `-beta-metrics`         | -            | `COUPER_BETA_METRICS`         | Option to enable the prometheus [metrics](./METRICS.md) exporter. |
+| `-beta-metrics-port`    | `9090`       | `COUPER_BETA_METRICS_PORT`    | Prometheus exporter listen port. |
+| `-beta-service-name`    | `couper`     | `COUPER_BETA_SERVICE_NAME`    | The service name which applies to the `service_name` metric labels. |

docs/METRICS.md

@@ -0,0 +1,30 @@
+- [Metrics](#metrics)
+    - [Prometheus](#prometheus)
+    - [Grafana Dashboard](#grafana-dashboard)
+      - [Preview](#preview)
+    - [Developers](#developers)
+
+# Metrics
+
+Our metrics feature is [beta](./BETA.md) for now. However, we want to provide some core metrics which can be directly collected from Couper.
+
+## Prometheus
+
+Couper provides a built-in [Prometheus](https://prometheus.io/) exporter. It is configurable with [settings](./REFERENCE.md#settings-block) like port or `service_name` label. If enabled the default scrape target port is `9090`.
+
+## Grafana Dashboard
+
+Couper provides a maintained Grafana dashboard which you can find here: [grafana.json](./../grafana.json)
+and import this JSON model to your grafana instance.
+You may have to set your Datasource to your Prometheus one.
+
+If you're missing some configuration options or have feedback: Feel free to open a [discussion](https://github.com/avenga/couper/discussions) or
+an [issue](https://github.com/avenga/couper/issues) if something does not work as expected or shown values does not make any sense.
+
+### Preview
+
+![dashboard](./img/grafana.png)
+
+## Developers
+
+If you are interested in contributing to our metrics or refine the grafana dashboard: `make docker-telemetry` will spin up the stack for you.

docs/REFERENCE.md

@@ -503,7 +503,10 @@ gateway instance.
 | `request_id_client_header`      | string | `Couper-Request-ID` | Name of a HTTP header field which Couper uses to transport the `request.id` to the client. |-|-|
 | `request_id_format`             | string | `common`            | If set to `uuid4` a rfc4122 uuid is used for `request.id` and related log fields. |-|-|
 | `secure_cookies`                | string | `""`                | If set to `"strip"`, the `Secure` flag is removed from all `Set-Cookie` HTTP header fields. |-|-|
-| `xfh`                           | bool   | `false`             | Option to use the `X-Forwarded-Host` header as the request host. |-|-|
+| `xfh`                           | bool   | `false`             | Option to use the `X-Forwarded-Host` header as the request host.  | - | - |
+| `beta_metrics`                  | bool   | `false`             | Option to enable the prometheus [metrics](./METRICS.md) exporter. | - | - |
+| `beta_metrics_port`             | number | `9090`              | Prometheus exporter listen port. | - | - |
+| `beta_service_name`             | string | `couper`            | The service name which applies to the `service_name` metric labels. | - | - |
 
 ### Defaults Block