Guard config CRUD metrics so it's safe for grafana-enterprise

Previous attempt to land this required this PR and a grafana-enterprise
PR to land at the ~same time.

This PR guards the use of `dsConfigHandlerRequestsDuration` with a nil
check, and doesn't change any existing APIs, so we can land it without
any timing issues with grafana-enterprise.

Once this has landed, we'll make a follow-up PR for grafana-enterprise.

pkg/registry/apis/datasource/legacy_store.go

@@ -61,20 +61,24 @@ func (s *legacyStorage) List(ctx context.Context, options *internalversion.ListO
 }
 
 func (s *legacyStorage) Get(ctx context.Context, name string, options *metav1.GetOptions) (runtime.Object, error) {
-	start := time.Now()
-	defer func() {
-		metricutil.ObserveWithExemplar(ctx, s.dsConfigHandlerRequestsDuration.WithLabelValues("new", "Get"), time.Since(start).Seconds())
-	}()
+	if s.dsConfigHandlerRequestsDuration != nil {
+		start := time.Now()
+		defer func() {
+			metricutil.ObserveWithExemplar(ctx, s.dsConfigHandlerRequestsDuration.WithLabelValues("new", "Get"), time.Since(start).Seconds())
+		}()
+	}
 
 	return s.datasources.GetDataSource(ctx, name)
 }
 
 // Create implements rest.Creater.
 func (s *legacyStorage) Create(ctx context.Context, obj runtime.Object, createValidation rest.ValidateObjectFunc, options *metav1.CreateOptions) (runtime.Object, error) {
-	start := time.Now()
-	defer func() {
-		metricutil.ObserveWithExemplar(ctx, s.dsConfigHandlerRequestsDuration.WithLabelValues("new", "Create"), time.Since(start).Seconds())
-	}()
+	if s.dsConfigHandlerRequestsDuration != nil {
+		start := time.Now()
+		defer func() {
+			metricutil.ObserveWithExemplar(ctx, s.dsConfigHandlerRequestsDuration.WithLabelValues("new", "Create"), time.Since(start).Seconds())
+		}()
+	}
 
 	ds, ok := obj.(*v0alpha1.DataSource)
 	if !ok {
@@ -85,10 +89,12 @@ func (s *legacyStorage) Create(ctx context.Context, obj runtime.Object, createVa
 
 // Update implements rest.Updater.
 func (s *legacyStorage) Update(ctx context.Context, name string, objInfo rest.UpdatedObjectInfo, createValidation rest.ValidateObjectFunc, updateValidation rest.ValidateObjectUpdateFunc, forceAllowCreate bool, options *metav1.UpdateOptions) (runtime.Object, bool, error) {
-	start := time.Now()
-	defer func() {
-		metricutil.ObserveWithExemplar(ctx, s.dsConfigHandlerRequestsDuration.WithLabelValues("new", "Create"), time.Since(start).Seconds())
-	}()
+	if s.dsConfigHandlerRequestsDuration != nil {
+		start := time.Now()
+		defer func() {
+			metricutil.ObserveWithExemplar(ctx, s.dsConfigHandlerRequestsDuration.WithLabelValues("new", "Create"), time.Since(start).Seconds())
+		}()
+	}
 
 	old, err := s.Get(ctx, name, &metav1.GetOptions{})
 	if err != nil {
@@ -126,10 +132,12 @@ func (s *legacyStorage) Update(ctx context.Context, name string, objInfo rest.Up
 
 // Delete implements rest.GracefulDeleter.
 func (s *legacyStorage) Delete(ctx context.Context, name string, deleteValidation rest.ValidateObjectFunc, options *metav1.DeleteOptions) (runtime.Object, bool, error) {
-	start := time.Now()
-	defer func() {
-		metricutil.ObserveWithExemplar(ctx, s.dsConfigHandlerRequestsDuration.WithLabelValues("new", "Create"), time.Since(start).Seconds())
-	}()
+	if s.dsConfigHandlerRequestsDuration != nil {
+		start := time.Now()
+		defer func() {
+			metricutil.ObserveWithExemplar(ctx, s.dsConfigHandlerRequestsDuration.WithLabelValues("new", "Create"), time.Since(start).Seconds())
+		}()
+	}
 
 	err := s.datasources.DeleteDataSource(ctx, name)
 	return nil, false, err

pkg/registry/apis/datasource/register.go

@@ -3,6 +3,7 @@ package datasource
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"maps"
 
@@ -38,14 +39,14 @@ var (
 // DataSourceAPIBuilder is used just so wire has something unique to return
 type DataSourceAPIBuilder struct {
 	datasourceResourceInfo utils.ResourceInfo
-
-	pluginJSON           plugins.JSONData
-	client               PluginClient // will only ever be called with the same plugin id!
-	datasources          PluginDatasourceProvider
-	contextProvider      PluginContextWrapper
-	accessControl        accesscontrol.AccessControl
-	queryTypes           *queryV0.QueryTypeDefinitionList
-	configCrudUseNewApis bool
+	pluginJSON             plugins.JSONData
+	client                 PluginClient // will only ever be called with the same plugin id!
+	datasources            PluginDatasourceProvider
+	contextProvider        PluginContextWrapper
+	accessControl          accesscontrol.AccessControl
+	queryTypes             *queryV0.QueryTypeDefinitionList
+	configCrudUseNewApis   bool
+	dataSourceCRUDMetric   *prometheus.HistogramVec
 }
 
 func RegisterAPIService(
@@ -66,6 +67,16 @@ func RegisterAPIService(
 	var err error
 	var builder *DataSourceAPIBuilder
 
+	dataSourceCRUDMetric := metricutil.NewHistogramVec(prometheus.HistogramOpts{
+		Namespace: "grafana",
+		Name:      "ds_config_handler_requests_duration_seconds",
+		Help:      "Duration of requests handled by datasource configuration handlers",
+	}, []string{"code_path", "handler"})
+	regErr := reg.Register(dataSourceCRUDMetric)
+	if regErr != nil && !errors.As(regErr, &prometheus.AlreadyRegisteredError{}) {
+		return nil, regErr
+	}
+
 	pluginJSONs, err := getDatasourcePlugins(pluginSources)
 	if err != nil {
 		return nil, fmt.Errorf("error getting list of datasource plugins: %s", err)
@@ -91,6 +102,7 @@ func RegisterAPIService(
 		if err != nil {
 			return nil, err
 		}
+		builder.SetDataSourceCRUDMetrics(dataSourceCRUDMetric)
 
 		apiRegistrar.RegisterAPI(builder)
 	}
@@ -161,6 +173,10 @@ func (b *DataSourceAPIBuilder) GetGroupVersion() schema.GroupVersion {
 	return b.datasourceResourceInfo.GroupVersion()
 }
 
+func (b *DataSourceAPIBuilder) SetDataSourceCRUDMetrics(datasourceCRUDMetric *prometheus.HistogramVec) {
+	b.dataSourceCRUDMetric = datasourceCRUDMetric
+}
+
 func addKnownTypes(scheme *runtime.Scheme, gv schema.GroupVersion) {
 	scheme.AddKnownTypes(gv,
 		&datasourceV0.DataSource{},
@@ -218,13 +234,9 @@ func (b *DataSourceAPIBuilder) UpdateAPIGroupInfo(apiGroupInfo *genericapiserver
 
 	if b.configCrudUseNewApis {
 		legacyStore := &legacyStorage{
-			datasources:  b.datasources,
-			resourceInfo: &ds,
-			dsConfigHandlerRequestsDuration: metricutil.NewHistogramVec(prometheus.HistogramOpts{
-				Namespace: "grafana",
-				Name:      "ds_config_handler_requests_duration_seconds",
-				Help:      "Duration of requests handled by datasource configuration handlers",
-			}, []string{"code_path", "handler"}),
+			datasources:                     b.datasources,
+			resourceInfo:                    &ds,
+			dsConfigHandlerRequestsDuration: b.dataSourceCRUDMetric,
 		}
 		unified, err := grafanaregistry.NewRegistryStore(opts.Scheme, ds, opts.OptsGetter)
 		if err != nil {