make use of new error reporting in the dispatcher.

staging/src/k8s.io/apiserver/pkg/admission/plugin/policy/validating/dispatcher.go

@@ -223,7 +223,7 @@ func (c *dispatcher) Dispatch(ctx context.Context, a admission.Attributes, o adm
 					switch decision.Action {
 					case ActionAdmit:
 						if decision.Evaluation == EvalError {
-							celmetrics.Metrics.ObserveAdmissionWithError(ctx, decision.Elapsed, definition.Name, binding.Name)
+							celmetrics.Metrics.ObserveAdmission(ctx, decision.Elapsed, definition.Name, binding.Name, ErrorType(&decision))
 						}
 					case ActionDeny:
 						for _, action := range binding.Spec.ValidationActions {

staging/src/k8s.io/apiserver/pkg/admission/plugin/policy/validating/errors.go

@@ -0,0 +1,38 @@
+/*
+Copyright 2024 The Kubernetes Authors.
+
+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 validating
+
+import (
+	"strings"
+
+	celmetrics "k8s.io/apiserver/pkg/admission/plugin/policy/validating/metrics"
+)
+
+// ErrorType decodes the error to determine the error type
+// that the metrics understand.
+func ErrorType(decision *PolicyDecision) celmetrics.ValidationErrorType {
+	if decision.Evaluation == EvalAdmit {
+		return celmetrics.ValidationNoError
+	}
+	if strings.HasPrefix(decision.Message, "compilation") {
+		return celmetrics.ValidationCompileError
+	}
+	if strings.HasPrefix(decision.Message, "validation failed due to running out of cost budget") {
+		return celmetrics.ValidatingOutOfBudget
+	}
+	return celmetrics.ValidatingInternalError
+}

staging/src/k8s.io/apiserver/pkg/admission/plugin/policy/validating/metrics/errors.go

@@ -0,0 +1,38 @@
+/*
+Copyright 2024 The Kubernetes Authors.
+
+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 cel
+
+import (
+	"errors"
+
+	apiservercel "k8s.io/apiserver/pkg/cel"
+)
+
+// ErrorType decodes the error to determine the error type
+// that the metrics understand.
+func ErrorType(err error) ValidationErrorType {
+	if err == nil {
+		return ValidationNoError
+	}
+	if errors.Is(err, apiservercel.ErrCompilation) {
+		return ValidationCompileError
+	}
+	if errors.Is(err, apiservercel.ErrOutOfBudget) {
+		return ValidatingOutOfBudget
+	}
+	return ValidatingInternalError
+}

staging/src/k8s.io/apiserver/pkg/admission/plugin/policy/validating/metrics/metrics.go

@@ -29,6 +29,22 @@ const (
 	metricsSubsystem = "validating_admission_policy"
 )
 
+// ValidationErrorType defines different error types that happen to a validation expression
+type ValidationErrorType string
+
+const (
+	// ValidationCompileError indicates that the expression fails to compile.
+	ValidationCompileError ValidationErrorType = "compile_error"
+	// ValidatingInternalError indicates that the expression fails due to internal
+	// errors that are out of the control of the user.
+	ValidatingInternalError ValidationErrorType = "internal_error"
+	// ValidatingOutOfBudget indicates that the expression fails due to running
+	// out of cost budget, or the budget cannot be obtained.
+	ValidatingOutOfBudget ValidationErrorType = "out_of_budget"
+	// ValidationNoError indicates that the expression returns without an error.
+	ValidationNoError ValidationErrorType = "no_error"
+)
+
 var (
 	// Metrics provides access to validation admission metrics.
 	Metrics = newValidationAdmissionMetrics()
@@ -81,8 +97,8 @@ func (m *ValidatingAdmissionPolicyMetrics) Reset() {
 	m.policyLatency.Reset()
 }
 
-// ObserveAdmissionWithError observes a policy validation error that was ignored due to failure policy.
-func (m *ValidatingAdmissionPolicyMetrics) ObserveAdmissionWithError(ctx context.Context, elapsed time.Duration, policy, binding string) {
+// ObserveAdmission observes a policy validation, with an optional error to indicate the error that may occur but ignored.
+func (m *ValidatingAdmissionPolicyMetrics) ObserveAdmission(ctx context.Context, elapsed time.Duration, policy, binding string, errorType ValidationErrorType) {
 	m.policyCheck.WithContext(ctx).WithLabelValues(policy, binding, "allow").Inc()
 	m.policyLatency.WithContext(ctx).WithLabelValues(policy, binding, "allow").Observe(elapsed.Seconds())
 }

staging/src/k8s.io/apiserver/pkg/admission/plugin/policy/validating/metrics/metrics_test.go

@@ -58,7 +58,7 @@ func TestNoUtils(t *testing.T) {
             apiserver_validating_admission_policy_check_total{enforcement_action="allow",policy="policy.example.com",policy_binding="binding.example.com"} 1
 			`,
 			observer: func() {
-				Metrics.ObserveAdmissionWithError(context.TODO(), time.Duration(10)*time.Second, "policy.example.com", "binding.example.com")
+				Metrics.ObserveAdmission(context.TODO(), time.Duration(10)*time.Second, "policy.example.com", "binding.example.com")
 			},
 		},
 		{