datastore/crdb: singleflight features

Only singleflight features internal to CRDB so that
it can be deduplicated in calls to Watch.

No other datastore has an expensive Features impl.

internal/datastore/crdb/crdb.go

@@ -17,6 +17,7 @@ import (
 	"github.com/shopspring/decimal"
 	"go.opentelemetry.io/otel"
 	"golang.org/x/sync/errgroup"
+	"resenje.org/singleflight"
 
 	datastoreinternal "github.com/authzed/spicedb/internal/datastore"
 	"github.com/authzed/spicedb/internal/datastore/common"
@@ -257,6 +258,8 @@ type crdbDatastore struct {
 
 	beginChangefeedQuery string
 
+	featureGroup singleflight.Group[string, *datastore.Features]
+
 	pruneGroup *errgroup.Group
 	ctx        context.Context
 	cancel     context.CancelFunc
@@ -419,6 +422,13 @@ func (cds *crdbDatastore) headRevisionInternal(ctx context.Context) (revision.De
 }
 
 func (cds *crdbDatastore) Features(ctx context.Context) (*datastore.Features, error) {
+	features, _, err := cds.featureGroup.Do(ctx, "", func(ictx context.Context) (*datastore.Features, error) {
+		return cds.features(ictx)
+	})
+	return features, err
+}
+
+func (cds *crdbDatastore) features(ctx context.Context) (*datastore.Features, error) {
 	var features datastore.Features
 
 	head, err := cds.HeadRevision(ctx)

internal/datastore/proxy/singleflight.go

@@ -20,7 +20,6 @@ type singleflightProxy struct {
 	optRevGroup   singleflight.Group[string, datastore.Revision]
 	checkRevGroup singleflight.Group[string, string]
 	statsGroup    singleflight.Group[string, datastore.Stats]
-	featureGroup  singleflight.Group[string, *datastore.Features]
 	delegate      datastore.Datastore
 }
 
@@ -63,20 +62,17 @@ func (p *singleflightProxy) Watch(ctx context.Context, afterRevision datastore.R
 	return p.delegate.Watch(ctx, afterRevision)
 }
 
-func (p *singleflightProxy) Features(ctx context.Context) (*datastore.Features, error) {
-	features, _, err := p.featureGroup.Do(ctx, "", func(ctx context.Context) (*datastore.Features, error) {
-		return p.delegate.Features(ctx)
-	})
-	return features, err
-}
-
 func (p *singleflightProxy) Statistics(ctx context.Context) (datastore.Stats, error) {
 	stats, _, err := p.statsGroup.Do(ctx, "", func(ctx context.Context) (datastore.Stats, error) {
 		return p.delegate.Statistics(ctx)
 	})
 	return stats, err
 }
 
+func (p *singleflightProxy) Features(ctx context.Context) (*datastore.Features, error) {
+	return p.delegate.Features(ctx)
+}
+
 func (p *singleflightProxy) ReadyState(ctx context.Context) (datastore.ReadyState, error) {
 	return p.delegate.ReadyState(ctx)
 }