[SharovBot] db/state: fix DATA RACE between Aggregator.Close and MergeLoop goroutine

db/kv/kv_interface.go

@@ -515,6 +515,10 @@ type TemporalDebugDB interface {
 
 	Files() []string
 	MergeLoop(ctx context.Context) error
+	// StartMergeLoopBackground spawns a background merge goroutine and registers
+	// it with the aggregator's WaitGroup before launching it, so that Close/
+	// wg.Wait cannot observe a zero count before the goroutine has started.
+	StartMergeLoopBackground(ctx context.Context, onErr func(error))
 }
 
 // FlushConfig holds optional behaviour for TemporalMemBatch.Flush, populated by

db/kv/remotedb/kv_remote.go

@@ -199,6 +199,9 @@ func (db *DB) EnableReadAhead() kv.TemporalDebugDB                 { panic("not
 func (db *DB) DisableReadAhead()                                   { panic("not implemented") }
 func (db *DB) Files() []string                                     { panic("not implemented") }
 func (db *DB) MergeLoop(ctx context.Context) error                 { panic("not implemented") }
+func (db *DB) StartMergeLoopBackground(_ context.Context, _ func(error)) {
+	panic("not implemented")
+}
 func (db *DB) BeginTemporalRo(ctx context.Context) (kv.TemporalTx, error) {
 	t, err := db.BeginRo(ctx) //nolint:gocritic
 	if err != nil {

db/kv/temporal/kv_temporal.go

@@ -718,6 +718,10 @@ func (db *DB) MergeLoop(ctx context.Context) error {
 	return db.stateFiles.MergeLoop(ctx)
 }
 
+func (db *DB) StartMergeLoopBackground(ctx context.Context, onErr func(error)) {
+	db.stateFiles.StartMergeLoopBackground(ctx, onErr)
+}
+
 func (tx *Tx) DomainFiles(domain ...kv.Domain) kv.VisibleFiles {
 	return tx.aggtx.DomainFiles(domain...)
 }

db/state/aggregator.go

@@ -1230,6 +1230,21 @@
 	return a.mergeLoop(ctx)
 }
 
+// StartMergeLoopBackground spawns a background goroutine that runs MergeLoop.
+// It calls wg.Add(1) synchronously before launching the goroutine, so that a
+// concurrent Close/wg.Wait can never observe a zero count before the merge
+// goroutine has registered itself. The caller should use this instead of
+// manually wrapping MergeLoop in a goroutine to avoid the wg.Add/wg.Wait race.
+func (a *Aggregator) StartMergeLoopBackground(ctx context.Context, onErr func(error)) {
+	a.wg.Add(1)
+	go func() {
+		defer a.wg.Done()
+		if err := a.mergeLoop(ctx); err != nil && onErr != nil {
+			onErr(err)
+		}
+	}()
+}
+
 func (a *Aggregator) mergeLoop(ctx context.Context) (err error) {
 	if dbg.NoMerge() || !a.mergingFiles.CompareAndSwap(false, true) {
 		return nil // currently merging or merge is prohibited

node/eth/backend.go

@@ -1129,11 +1129,9 @@ func New(ctx context.Context, stack *node.Node, config *ethconfig.Config, logger
 	}
 
 	if !dbg.NoBackgroundMaintenance() {
-		go func() {
-			if err := temporalDb.Debug().MergeLoop(ctx); err != nil {
-				logger.Error("snapashot merge loop error", "err", err)
-			}
-		}()
+		temporalDb.Debug().StartMergeLoopBackground(ctx, func(err error) {
+			logger.Error("snapashot merge loop error", "err", err)
+		})
 	}
 
 	return backend, nil