[stable/nginx-ingress] Add prometheus rule (#16370)

* Added prometheusRules support

- Bump Charts.yaml
- Added prometheusRules resource template
- Added new variables in README
- Added new variables default values in values.yaml

Signed-off-by: Alejandro Garrido Mota <garridomota@gmail.com>

* Removed trailing space in order to pass helm lint, my local helm
lint didn't detect it :-(

Signed-off-by: Alejandro Garrido Mota <garridomota@gmail.com>

* Bump it to 1.16.0 because is a new feature

Signed-off-by: Alejandro Garrido Mota <garridomota@gmail.com>

stable/nginx-ingress/Chart.yaml

@@ -1,6 +1,6 @@
 apiVersion: v1
 name: nginx-ingress
-version: 1.15.1
+version: 1.16.0
 appVersion: 0.25.1
 home: https://github.com/kubernetes/ingress-nginx
 description: An nginx Ingress controller that uses ConfigMap to store the nginx configuration.

stable/nginx-ingress/README.md

@@ -138,6 +138,10 @@ Parameter | Description | Default
 `controller.metrics.serviceMonitor.additionalLabels` | Additional labels that can be used so ServiceMonitor will be discovered by Prometheus | `{}`
 `controller.metrics.serviceMonitor.namespace` | namespace where servicemonitor resource should be created | `the same namespace as nginx ingress`
 `controller.metrics.serviceMonitor.honorLabels` | honorLabels chooses the metric's labels on collisions with target labels. | `false`
+`controller.metrics.prometheusRule.enabled` | Set this to `true` to create prometheusRules for Prometheus operator | `false`
+`controller.metrics.prometheusRule.additionalLabels` | Additional labels that can be used so prometheusRules will be discovered by Prometheus | `{}`
+`controller.metrics.prometheusRule.namespace` | namespace where prometheusRules resource should be created | `the same namespace as nginx ingress`
+`controller.metrics.prometheusRule.rules` | [rules](https://prometheus.io/docs/prometheus/latest/configuration/alerting_rules/) to be prometheus in YAML format, check values for an example. | `[]`
 `controller.customTemplate.configMapName` | configMap containing a custom nginx template | `""`
 `controller.customTemplate.configMapKey` | configMap key containing the nginx template | `""`
 `controller.addHeaders` | configMap key:value pairs containing [custom headers](https://kubernetes.github.io/ingress-nginx/user-guide/nginx-configuration/configmap/#add-headers) added before sending response to the client | `{}`

stable/nginx-ingress/templates/controller-prometheusrules.yaml

@@ -0,0 +1,24 @@
+{{- if and .Values.controller.metrics.enabled .Values.controller.metrics.prometheusRule.enabled }}
+apiVersion: monitoring.coreos.com/v1
+kind: PrometheusRule
+metadata:
+  name: {{ template "nginx-ingress.controller.fullname" . }}
+  {{- if .Values.controller.metrics.prometheusRule.namespace }}
+  namespace: {{ .Values.controller.metrics.prometheusRule.namespace }}
+  {{- end }}
+  labels:
+    app: {{ template "nginx-ingress.name" . }}
+    chart: {{ .Chart.Name }}-{{ .Chart.Version }}
+    component: "{{ .Values.controller.name }}"
+    heritage: {{ .Release.Service }}
+    release: {{ .Release.Name }}
+    {{- if .Values.controller.metrics.prometheusRule.additionalLabels }}
+{{ toYaml .Values.controller.metrics.prometheusRule.additionalLabels | indent 4 }}
+    {{- end }}
+spec:
+  {{- with .Values.controller.metrics.prometheusRule.rules }}
+  groups:
+  - name: {{ template "nginx-ingress.name" $ }}
+    rules: {{- toYaml . | nindent 4 }}
+  {{- end }}
+{{- end }}

stable/nginx-ingress/values.yaml

@@ -334,6 +334,30 @@ controller:
       namespace: ""
       # honorLabels: true
 
+    prometheusRule:
+      enabled: false
+      additionalLabels: {}
+      namespace: ""
+      rules: []
+        # # These are just examples rules, please adapt them to your needs
+        # - alert: TooMany500s
+        #   expr: 100 * ( sum( nginx_ingress_controller_requests{status=~"5.+"} ) / sum(nginx_ingress_controller_requests) ) > 5
+        #   for: 1m
+        #   labels:
+        #     severity: critical
+        #   annotations:
+        #     description: Too many 5XXs
+        #     summary: More than 5% of the all requests did return 5XX, this require your attention
+        # - alert: TooMany400s
+        #   expr: 100 * ( sum( nginx_ingress_controller_requests{status=~"4.+"} ) / sum(nginx_ingress_controller_requests) ) > 5
+        #   for: 1m
+        #   labels:
+        #     severity: critical
+        #   annotations:
+        #     description: Too many 4XXs
+        #     summary: More than 5% of the all requests did return 4XX, this require your attention
+
+
   lifecycle: {}
 
   priorityClassName: ""