Register external datasource plugins on startup

Current code only registers core datasource k8s api groups.

Add external plugins.

Companion grafana-enterprise PR:

https://github.com/grafana/grafana-enterprise/pull/10125

pkg/registry/apis/datasource/register.go

@@ -3,10 +3,8 @@ package datasource
 import (
 	"context"
 	"encoding/json"
-	"errors"
 	"fmt"
 	"maps"
-	"path/filepath"
 
 	"github.com/prometheus/client_golang/prometheus"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -23,7 +21,6 @@ import (
 	datasourceV0 "github.com/grafana/grafana/pkg/apis/datasource/v0alpha1"
 	queryV0 "github.com/grafana/grafana/pkg/apis/query/v0alpha1"
 	grafanaregistry "github.com/grafana/grafana/pkg/apiserver/registry/generic"
-	"github.com/grafana/grafana/pkg/configprovider"
 	"github.com/grafana/grafana/pkg/plugins"
 	"github.com/grafana/grafana/pkg/plugins/manager/sources"
 	"github.com/grafana/grafana/pkg/promlib/models"
@@ -31,7 +28,6 @@ import (
 	"github.com/grafana/grafana/pkg/services/accesscontrol"
 	"github.com/grafana/grafana/pkg/services/apiserver/builder"
 	"github.com/grafana/grafana/pkg/services/featuremgmt"
-	"github.com/grafana/grafana/pkg/setting"
 	"github.com/grafana/grafana/pkg/tsdb/grafana-testdata-datasource/kinds"
 )
 
@@ -53,7 +49,6 @@ type DataSourceAPIBuilder struct {
 }
 
 func RegisterAPIService(
-	cfgProvider configprovider.ConfigProvider,
 	features featuremgmt.FeatureToggles,
 	apiRegistrar builder.APIRegistrar,
 	pluginClient plugins.Client, // access to everything
@@ -61,6 +56,7 @@ func RegisterAPIService(
 	contextProvider PluginContextWrapper,
 	accessControl accesscontrol.AccessControl,
 	reg prometheus.Registerer,
+	pluginSources sources.Registry,
 ) (*DataSourceAPIBuilder, error) {
 	// We want to expose just a limited set of plugins
 	//nolint:staticcheck // not yet migrated to OpenFeature
@@ -75,13 +71,9 @@ func RegisterAPIService(
 	var err error
 	var builder *DataSourceAPIBuilder
 
-	cfg, err := cfgProvider.Get(context.Background())
+	pluginJSONs, err := getDatasourcePlugins(pluginSources)
 	if err != nil {
-		return nil, err
-	}
-	pluginJSONs, err := getCorePlugins(cfg)
-	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("error getting list of datasource plugins: %s", err)
 	}
 
 	ids := []string{
@@ -299,21 +291,29 @@ func (b *DataSourceAPIBuilder) GetOpenAPIDefinitions() openapi.GetOpenAPIDefinit
 	}
 }
 
-func getCorePlugins(cfg *setting.Cfg) ([]plugins.JSONData, error) {
-	coreDataSourcesPath := filepath.Join(cfg.StaticRootPath, "app", "plugins", "datasource")
-	coreDataSourcesSrc := sources.NewLocalSource(
-		plugins.ClassCore,
-		[]string{coreDataSourcesPath},
-	)
+func getDatasourcePlugins(pluginSources sources.Registry) ([]plugins.JSONData, error) {
+	var pluginJSONs []plugins.JSONData
 
-	res, err := coreDataSourcesSrc.Discover(context.Background())
-	if err != nil {
-		return nil, errors.New("failed to load core data source plugins")
-	}
+	// It's possible that the same plugin will be found in different sources.
+	// Registering the same plugin twice in the API is Probably A Bad Thing,
+	// so this map keeps track of uniques, so we can skip duplicates.
+	var uniquePlugins = map[string]bool{}
 
-	pluginJSONs := make([]plugins.JSONData, 0, len(res))
-	for _, p := range res {
-		pluginJSONs = append(pluginJSONs, p.Primary.JSONData)
+	for _, pluginSource := range pluginSources.List(context.Background()) {
+		res, err := pluginSource.Discover(context.Background())
+		if err != nil {
+			return nil, err
+		}
+		for _, p := range res {
+			if p.Primary.JSONData.Type == plugins.TypeDataSource {
+				if _, found := uniquePlugins[p.Primary.JSONData.ID]; found {
+					backend.Logger.Info("Found duplicate plugin %s when registering API groups.", p.Primary.JSONData.ID)
+					continue
+				}
+				uniquePlugins[p.Primary.JSONData.ID] = true
+				pluginJSONs = append(pluginJSONs, p.Primary.JSONData)
+			}
+		}
 	}
 	return pluginJSONs, nil
 }