QueryService: Add feature toggles to better support testing (#86493)

pkg/registry/apis/query/README.md

@@ -0,0 +1,78 @@
+# Query service
+
+This query service aims to replace the existing /api/ds/query.  
+
+The key differences are:
+1. This service has a stronger type system (not simplejson)
+2. Same workflow regardless if expressions exist
+3. Datasource settings+access is managed in each datasource, not at the beginning
+
+
+
+### Current /api/ds/query workflow
+
+```mermaid
+sequenceDiagram
+    autonumber
+    actor User as User or Process
+    participant api as /api/ds/query
+    participant db as Storage<br/>(SQL)
+    participant ds as Datasource<br/>Plugin
+    participant expr as Expression<br/>Engine
+
+    User->>api: POST Query
+    loop Each query
+        api->>api: Parse query
+        api->>db: Get ds config<br>and secrets
+        db->>api: 
+    end
+    alt No expressions
+      alt Single datasource
+          api->>ds: QueryData
+      else Multiple datasources
+        loop Each datasource (concurrently)
+          api->>ds: QueryData
+        end
+        api->>api: Wait for results
+      end
+    else Expressions exist
+        api->>expr: Calculate expressions graph
+        loop Each node (eg, refID)
+          alt Is query
+              expr->>ds: QueryData
+          else Is expression
+            expr->>expr: Process
+          end
+        end
+    end
+    api->>User: return results
+```
+
+
+
+### /apis/query.grafana.app (in single tenant grafana)
+
+```mermaid
+sequenceDiagram
+    autonumber
+    actor User as User or Process
+    participant api as /apis/query.grafana.app
+    participant ds as Datasource<br/>Handler/Plugin
+    participant db as Storage<br/>(SQL)
+    participant expr as Expression<br/>Engine
+
+    User->>api: POST Query
+    api->>api: Parse queries
+    api->>api: Calculate dependencies
+    loop Each datasource (concurrently)
+        api->>ds: QueryData
+        ds->>ds: Verify user access
+        ds->>db: Get settings <br> and secrets
+    end
+    loop Each expression
+        api->>expr: Execute
+    end
+    api->>api: Verify ResultExpectations
+    api->>User: return results
+```
+

pkg/registry/apis/query/client/plugin.go

@@ -40,7 +40,7 @@ type pluginRegistry struct {
 var _ data.QueryDataClient = (*pluginClient)(nil)
 var _ query.DataSourceApiServerRegistry = (*pluginRegistry)(nil)
 
-// NewDummyTestRunner creates a runner that only works with testdata
+// NewQueryClientForPluginClient creates a client that delegates to the internal plugins.Client stack
 func NewQueryClientForPluginClient(p plugins.Client, ctx *plugincontext.Provider) data.QueryDataClient {
 	return &pluginClient{
 		pluginClient: p,

pkg/registry/apis/query/plugins.go

@@ -9,7 +9,6 @@ import (
 	"k8s.io/apiserver/pkg/registry/rest"
 
 	common "github.com/grafana/grafana/pkg/apimachinery/apis/common/v0alpha1"
-	example "github.com/grafana/grafana/pkg/apis/example/v0alpha1"
 	query "github.com/grafana/grafana/pkg/apis/query/v0alpha1"
 )
 
@@ -24,6 +23,9 @@ type pluginsStorage struct {
 	resourceInfo   *common.ResourceInfo
 	tableConverter rest.TableConvertor
 	registry       query.DataSourceApiServerRegistry
+
+	// Always return an empty list regardless what we think exists
+	returnEmptyList bool
 }
 
 func newPluginsStorage(reg query.DataSourceApiServerRegistry) *pluginsStorage {
@@ -46,7 +48,7 @@ func (s *pluginsStorage) NamespaceScoped() bool {
 }
 
 func (s *pluginsStorage) GetSingularName() string {
-	return example.DummyResourceInfo.GetSingularName()
+	return s.resourceInfo.GetSingularName()
 }
 
 func (s *pluginsStorage) NewList() runtime.Object {
@@ -58,5 +60,8 @@ func (s *pluginsStorage) ConvertToTable(ctx context.Context, object runtime.Obje
 }
 
 func (s *pluginsStorage) List(ctx context.Context, options *internalversion.ListOptions) (runtime.Object, error) {
+	if s.returnEmptyList {
+		return s.NewList(), nil
+	}
 	return s.registry.GetDatasourceApiServers(ctx)
 }

pkg/registry/apis/query/register.go

@@ -85,8 +85,9 @@ func RegisterAPIService(features featuremgmt.FeatureToggles,
 	tracer tracing.Tracer,
 	legacy service.LegacyDataSourceLookup,
 ) (*QueryAPIBuilder, error) {
-	if !features.IsEnabledGlobally(featuremgmt.FlagGrafanaAPIServerWithExperimentalAPIs) {
-		return nil, nil // skip registration unless opting into experimental apis
+	if !(features.IsEnabledGlobally(featuremgmt.FlagQueryService) ||
+		features.IsEnabledGlobally(featuremgmt.FlagGrafanaAPIServerWithExperimentalAPIs)) {
+		return nil, nil // skip registration unless explicitly added (or all experimental are added)
 	}
 
 	builder, err := NewQueryAPIBuilder(
@@ -132,10 +133,16 @@ func (b *QueryAPIBuilder) GetAPIGroupInfo(
 	gv := v0alpha1.SchemeGroupVersion
 	apiGroupInfo := genericapiserver.NewDefaultAPIGroupInfo(gv.Group, scheme, metav1.ParameterCodec, codecs)
 
-	plugins := newPluginsStorage(b.registry)
-
 	storage := map[string]rest.Storage{}
+
+	plugins := newPluginsStorage(b.registry)
 	storage[plugins.resourceInfo.StoragePath()] = plugins
+	if !b.features.IsEnabledGlobally(featuremgmt.FlagGrafanaAPIServerWithExperimentalAPIs) {
+		// The plugin registry is still experimental, and not yet accurate
+		// For standard k8s api discovery to work, at least one resource must be registered
+		// While this feature is under development, we can return an empty list for non-dev instances
+		plugins.returnEmptyList = true
+	}
 
 	apiGroupInfo.VersionedResourcesStorageMap[gv.Version] = storage
 	return &apiGroupInfo, nil