better error message

weed/filer/mongodb/mongodb_store.go

@@ -109,6 +109,10 @@ func (store *MongodbStore) InsertEntry(ctx context.Context, entry *filer.Entry)
 		Meta:      meta,
 	})
 
+	if err != nil {
+		return fmt.Errorf("InsertEntry %st: %v", entry.FullPath, err)
+	}
+
 	return nil
 }
 
@@ -124,6 +128,7 @@ func (store *MongodbStore) FindEntry(ctx context.Context, fullpath util.FullPath
 	var where = bson.M{"directory": dir, "name": name}
 	err = store.connect.Database(store.database).Collection(store.collectionName).FindOne(ctx, where).Decode(&data)
 	if err != mongo.ErrNoDocuments && err != nil {
+		glog.Error("find %s: %v", fullpath, err)
 		return nil, filer_pb.ErrNotFound
 	}