kube-vip: optional Prometheus metrics (default port 2112) (#13229)

Add kube_vip_metrics_enabled and kube_vip_metrics_port; wire
prometheus_server and container port in the static pod manifest.
Default metrics port to 2112 to match kube-vip upstream. Document
and sample inventory updated.

roles/kubernetes/node/defaults/main.yml

@@ -88,6 +88,9 @@ kube_vip_retryperiod: 1
 kube_vip_enable_node_labeling: false
 kube_vip_bgp_sourceip:
 kube_vip_bgp_sourceif:
+kube_vip_metrics_enabled: false
+# TCP port for kube-vip Prometheus metrics; manifest sets prometheus_server to :PORT (same as kube-vip upstream default, see cmd/kube-vip.go).
+kube_vip_metrics_port: 2112
 
 # Requests for load balancer app
 loadbalancer_apiserver_memory_requests: 32M

roles/kubernetes/node/templates/manifests/kube-vip.manifest.j2

@@ -109,11 +109,21 @@ spec:
 {% if kube_vip_lb_fwdmethod %}
     - name: lb_fwdmethod
       value: {{ kube_vip_lb_fwdmethod | string | to_json }}
+{% endif %}
+{% if kube_vip_metrics_enabled %}
+    - name: prometheus_server
+      value: {{ (':' ~ (kube_vip_metrics_port | string)) | to_json }}
 {% endif %}
     image: {{ kube_vip_image_repo }}:{{ kube_vip_image_tag }}
     imagePullPolicy: {{ k8s_image_pull_policy }}
     name: kube-vip
     resources: {}
+{% if kube_vip_metrics_enabled %}
+    ports:
+    - name: metrics
+      containerPort: {{ kube_vip_metrics_port }}
+      protocol: TCP
+{% endif %}
 {% if kube_vip_lb_fwdmethod == "masquerade" %}
     securityContext:
       privileged: true