prometheus-operator: allow to disable webhooks

This is needed to install this component on AKS with Kubernetes 1.16.3.

See #219 for more details.

Signed-off-by: Mateusz Gozdek <mateusz@kinvolk.io>

docs/configuration-reference/components/prometheus-operator.md

@@ -97,6 +97,7 @@ Example:
 | `alertmanager_external_url` | The external URL the Alertmanager instances will be available under. This is necessary to generate correct URLs. This is necessary if Alertmanager is not served from root of a DNS name. | "" | false |
 | `alertmanager_config` | Provide YAML file path to configure Alertmanager. See [https://prometheus.io/docs/alerting/configuration/#configuration-file](https://prometheus.io/docs/alerting/configuration/#configuration-file). | `{"global":{"resolve_timeout":"5m"},"route":{"group_by":["job"],"group_wait":"30s","group_interval":"5m","repeat_interval":"12h","receiver":"null","routes":[{"match":{"alertname":"Watchdog"},"receiver":"null"}]},"receivers":[{"name":"null"}]}` | false |
 | `alertmanager_node_selector` | Node selector to specify nodes where the AlertManager pods should be deployed. | {} | false |
+| `disable_webhooks` | Disables validation and mutation webhooks. This might be required on older versions of Kubernetes to install successfully. | false | false |
 
 ## Applying
 

pkg/components/prometheus-operator/component.go

@@ -48,6 +48,8 @@ type component struct {
 	AlertManagerExternalURL  string            `hcl:"alertmanager_external_url,optional"`
 	AlertManagerConfig       string            `hcl:"alertmanager_config,optional"`
 	AlertManagerNodeSelector map[string]string `hcl:"alertmanager_node_selector,optional"`
+
+	DisableWebhooks bool `hcl:"disable_webhooks,optional"`
 }
 
 func newComponent() *component {

pkg/components/prometheus-operator/template.go

@@ -56,12 +56,20 @@ kubeEtcd:
   endpoints: {{.EtcdEndpoints}}
 prometheus-node-exporter:
   service: {}
-{{ if .PrometheusOperatorNodeSelector }}
+{{ if (or .PrometheusOperatorNodeSelector .DisableWebhooks) }}
 prometheusOperator:
+  {{- if .DisableWebhooks }}
+  tlsProxy:
+    enabled: false
+  admissionWebhooks:
+    enabled: false
+  {{- end }}
+	{{- if .PrometheusOperatorNodeSelector }}
   nodeSelector:
     {{ range $key, $value := .PrometheusOperatorNodeSelector }}
     {{ $key }}: {{ $value }}
     {{ end }}
+	{{- end }}
 {{ end }}
 prometheus:
   prometheusSpec: