Add Prometheus example

.github/workflows/pr.yml

@@ -27,15 +27,18 @@ jobs:
     steps:
     - name: Check out code into the Go module directory
       uses: actions/checkout@v2
-    - name: System tests
+    - name: Dry run examples
       run: |
         curl -s "https://raw.githubusercontent.com/kubernetes-sigs/kustomize/master/hack/install_kustomize.sh"  | bash
         export GOPATH=$HOME/go
         export PATH=$PATH:$GOPATH/bin
         make install-tools
         kind create cluster --image kindest/node:v1.19.1
         kubectl apply --validate=false -f https://github.com/jetstack/cert-manager/releases/latest/download/cert-manager.crds.yaml
+        # Create CRD PodMonitor without running Prometheus operator
+        curl https://raw.githubusercontent.com/prometheus-operator/prometheus-operator/master/bundle.yaml | sed "s/replicas: 1$/replicas: 0/" | kubectl apply -f -
         make install
+        sleep 3 # otherwise we sporadically observe 'no matches for kind "RabbitmqCluster" in version "rabbitmq.com/v1beta1'
         kubectl apply --dry-run=server --recursive -f docs/examples/
 
   system_tests:

docs/examples/prometheus/README.md

@@ -0,0 +1,11 @@
+# Prometheus Example
+
+See [Monitoring RabbitMQ in Kubernetes](https://www.rabbitmq.com/kubernetes/operator/operator-monitoring.html) for detailed instructions.
+
+If you deployed the [Prometheus Operator](https://github.com/prometheus-operator/prometheus-operator), make Prometheus scrape RabbitMQ nodes by:
+```shell
+kubectl apply -f rabbitmq-podmonitor.yaml
+```
+
+Alternatively, if you deployed the Prometheus Operator via the [kube-prometheus-stack](https://github.com/prometheus-community/helm-charts/tree/main/charts/kube-prometheus-stack) Helm chart,
+set the values in [kube-prometheus-stack-values.yaml.example](kube-prometheus-stack-values.yaml.example) when installing / upgrading the Helm chart.

docs/examples/prometheus/kube-prometheus-stack-values.yaml.example

@@ -0,0 +1,11 @@
+---
+prometheus:
+  additionalPodMonitors:
+   - name: rabbitmq
+     podMetricsEndpoints:
+     - port: prometheus
+     selector:
+       matchLabels:
+         app.kubernetes.io/component: rabbitmq
+     namespaceSelector:
+       any: true

docs/examples/prometheus/rabbitmq-podmonitor.yaml

@@ -0,0 +1,14 @@
+---
+apiVersion: monitoring.coreos.com/v1
+kind: PodMonitor
+metadata:
+  name: rabbitmq
+spec:
+  podMetricsEndpoints:
+  - interval: 15s
+    port: prometheus
+  selector:
+    matchLabels:
+      app.kubernetes.io/component: rabbitmq
+  namespaceSelector:
+    any: true