webhook: adds an example of PrometheusRule validation with operator

 This commits adds extra webhook, which is able to validate metricsQL
 expressions with PrometheusRule objects.

Author: f41gh7

internal/manager/manager.go

@@ -369,6 +369,7 @@ func addWebhooks(mgr ctrl.Manager) error {
 		webhookv1beta1.SetupVMScrapeConfigWebhookWithManager,
 		webhookv1beta1.SetupVMStaticScrapeWebhookWithManager,
 		webhookv1beta1.SetupVMProbeWebhookWithManager,
+		webhookv1.SetupPromethuesRuleWebhookWithManager,
 	})
 }
 

internal/webhook/operator/v1/prometheusrule_webhook.go

@@ -0,0 +1,94 @@
+/*
+
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package v1
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+
+	promv1 "github.com/prometheus-operator/prometheus-operator/pkg/apis/monitoring/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+	ctrl "sigs.k8s.io/controller-runtime"
+	"sigs.k8s.io/controller-runtime/pkg/webhook/admission"
+
+	vmv1beta1 "github.com/VictoriaMetrics/operator/api/operator/v1beta1"
+	"github.com/VictoriaMetrics/operator/internal/config"
+	"github.com/VictoriaMetrics/operator/internal/controller/operator/converter"
+)
+
+// SetupVLClusterWebhookWithManager will setup the manager to manage the webhooks
+func SetupPromethuesRuleWebhookWithManager(mgr ctrl.Manager) error {
+	println("setting up")
+	return ctrl.NewWebhookManagedBy(mgr).
+		For(&promv1.PrometheusRule{}).
+		WithValidator(&PrometheusRuleValidator{}).
+		Complete()
+}
+
+type PrometheusRuleValidator struct{}
+
+var _ admission.CustomValidator = (*PrometheusRuleValidator)(nil)
+
+// ValidateCreate implements admission.CustomValidator so a webhook will be registered for the type
+func (*PrometheusRuleValidator) ValidateCreate(_ context.Context, obj runtime.Object) (admission.Warnings, error) {
+	r, ok := obj.(*promv1.PrometheusRule)
+	if !ok {
+		return nil, fmt.Errorf("BUG: unexpected type: %T", obj)
+	}
+
+	vmr := converter.ConvertPromRule(r, config.MustGetBaseConfig())
+
+	if err := vmr.Validate(); err != nil {
+		return nil, err
+	}
+
+	return nil, nil
+}
+
+// ValidateUpdate implements admission.CustomValidator so a webhook will be registered for the type
+func (*PrometheusRuleValidator) ValidateUpdate(_ context.Context, _, newObj runtime.Object) (admission.Warnings, error) {
+	r, ok := newObj.(*promv1.PrometheusRule)
+	if !ok {
+		return nil, fmt.Errorf("BUG: unexpected type: %T", newObj)
+	}
+
+	vmr := converter.ConvertPromRule(r, config.MustGetBaseConfig())
+
+	if err := vmr.Validate(); err != nil {
+		return nil, err
+	}
+	return nil, nil
+}
+
+// ValidateDelete implements admission.CustomValidator so a webhook will be registered for the type
+func (*PrometheusRuleValidator) ValidateDelete(_ context.Context, _ runtime.Object) (admission.Warnings, error) {
+	return nil, nil
+}
+
+func promRuleSpecToVMRule(src *promv1.PrometheusRule) (*vmv1beta1.VMRule, error) {
+	var vr vmv1beta1.VMRule
+	specData, err := json.Marshal(src.Spec)
+	if err != nil {
+		return nil, err
+	}
+
+	if err := json.Unmarshal(specData, &vr.Spec); err != nil {
+		return nil, err
+	}
+	return &vr, nil
+}