[#947] engine: Evacuate trees to local shards

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

pkg/local_object_storage/pilorama/boltdb.go

@@ -549,6 +549,58 @@ func (t *boltForest) TreeApply(ctx context.Context, cnr cidSDK.ID, treeID string
 	return metaerr.Wrap(err)
 }
 
+// TreeApplyStream should be used with caution: this method locks other write transactions while `source` is not closed.
+func (t *boltForest) TreeApplyStream(ctx context.Context, cnr cidSDK.ID, treeID string, source <-chan *Move) error {
+	var (
+		startedAt = time.Now()
+		success   = false
+	)
+	defer func() {
+		t.metrics.AddMethodDuration("TreeApplyStream", time.Since(startedAt), success)
+	}()
+
+	_, span := tracing.StartSpanFromContext(ctx, "boltForest.TreeApplyStream",
+		trace.WithAttributes(
+			attribute.String("container_id", cnr.EncodeToString()),
+			attribute.String("tree_id", treeID),
+		),
+	)
+	defer span.End()
+
+	t.modeMtx.RLock()
+	defer t.modeMtx.RUnlock()
+
+	if t.mode.NoMetabase() {
+		return ErrDegradedMode
+	} else if t.mode.ReadOnly() {
+		return ErrReadOnlyMode
+	}
+
+	fullID := bucketName(cnr, treeID)
+	err := metaerr.Wrap(t.db.Update(func(tx *bbolt.Tx) error {
+		bLog, bTree, err := t.getTreeBuckets(tx, fullID)
+		if err != nil {
+			return err
+		}
+		for {
+			select {
+			case <-ctx.Done():
+				return ctx.Err()
+			case m, ok := <-source:
+				if !ok {
+					return nil
+				}
+				var lm Move
+				if e := t.applyOperation(bLog, bTree, []*Move{m}, &lm); e != nil {
+					return e
+				}
+			}
+		}
+	}))
+	success = err == nil
+	return err
+}
+
 func (t *boltForest) addBatch(cnr cidSDK.ID, treeID string, m *Move, ch chan error) {
 	t.mtx.Lock()
 	for i := 0; i < len(t.batches); i++ {