Document usage in combination with Prometheus operator

Author: ewoutp

README.md

@@ -18,6 +18,11 @@ This results in an ArangoDB Exporter exposing all statistics of
 the ArangoDB server (running at `http://<your-database-host>:8529`)
 at `http://<your-host-ip>:9101/metrics`.
 
+## Running in Docker
+
+To run the ArangoDB Exporter in docker, use an image such as
+[`arangodb/arangodb-exporter:0.1.3`](https://hub.docker.com/r/arangodb/arangodb-exporter/).
+
 ## Configuring Prometheus
 
 There are several ways to configure Prometheus to fetch metrics from the ArangoDB Exporter.
@@ -36,6 +41,56 @@ scrape_configs:
 
 For more info on configuring Prometheus go to [its configuration documentation](https://prometheus.io/docs/prometheus/latest/configuration/configuration).
 
+If you're using the [Prometheus Operator](https://github.com/coreos/prometheus-operator)
+in Kubernetes, you need to create an additional `Service` and a `ServiceMonitor` resource
+like this:
+
+```yaml
+kind: Service
+apiVersion: v1
+metadata:
+  name: arangodb-exporters-service
+  labels:
+    app: arangodb-exporter
+spec:
+  selector:
+    app: arangodb-exporter
+  ports:
+  - name: metrics
+    port: 9101
+
+---
+
+apiVersion: monitoring.coreos.com/v1
+kind: ServiceMonitor
+metadata:
+  name: arangodb-exporter
+  namespace: monitoring
+  labels:
+    team: frontend
+    prometheus: kube-prometheus
+spec:
+  namespaceSelector:
+    matchNames:
+    - default
+  selector:
+    matchLabels:
+      app: arangodb-exporter
+  endpoints:
+  - port: metrics
+    scheme: https
+    tlsConfig:
+      insecureSkipVerify: true
+```
+
+Note 1: that the typical deployment on the Prometheus operator is done in
+a namespace called `monitoring`. Make sure to match the `namespace`
+of the `ServiceMonitor` to match that.
+
+Note 2: that the `Prometheus` custom resource has a field called `serviceMonitorSelector`.
+Make sure that the `matchLabels` selector in there matches the labels of
+your `ServiceMonitor`.
+
 ## Building
 
 To build this project, you need Go 1.8 or higher and Docker installed.