nodejs/exceljs. Из-за чего происходит утечка памяти?

 async getAll() {
        var th = this;
        var categories = require("./cat_test");
        var numProducts = 0;



        for (var id in categories) {
            this.clientDb = await DB.connect();
            this.db = this.clientDb.db("ozon");
            this.collection = this.db.collection("stat");
            var row = 2;
            var mainCategoryName = categories[id].name; //имя главной категории
            var c1 = categories[id];
            var filename = "xlsx/all/"+mainCategoryName+"_" + new Date().format("dd-MM-Y") + ".xlsx";
            const options = {
                writer: 'stream',
                filename: filename,
                useStyles: true,
                useSharedStrings: true
            };
            var wb = new WorkbookWriter(options);
            var worksheet = wb.addWorksheet("List1");
            worksheet.columns = require("./columns");

            for (var subc in c1.items.categories) {
                var promises = [], promisesDB = [];
                var c2 = c1.items.categories[subc];
                var subCategoryId = c2.id; //ID подкатегории
                var subCategoryName = c2.title; //имя подкатегории

                for (var subc2 in c2.categories) {
                    var c3 = c2.categories[subc2];
                    var subCategory2Id = c3.id; //ID 2 подкатегории
                    var subCategory2Name = c3.title; //название 2 подкатегории
                    var subCategory2Url = c3.url; //ссылка на вторую категорию
                    var numPages = await this.getNumPages(subCategory2Url);
                    this.log(mainCategoryName + ">" + subCategoryName + ">" + subCategory2Name);
                    for (var page = 1; page <= numPages[0]; page++) {
                        var params = {
                            "url": subCategory2Url + "?layout_container=categorySearchMegapagination&page=" + page
                        };
                        var res = await this.req("https://www.ozon.ru/api/composer-api.bx/page/json/v1", params);
                        try {
                            var keys = Object.keys(res.body.catalog.searchResultsV2);
                        } catch (e) {
                            this.tg(e + "\n\n" + JSON.stringify(res.body.catalog));
                            fs.writeFileSync("searchResults-error-" + Math.floor(Math.random() * 10000) + "-" + new Date().format("dd-MM-Y") + ".log", e + "\n\n" + JSON.stringify(res.body));
                            continue;
                        }
                        var products = res.body.catalog.searchResultsV2[keys[keys.length - 1]].items;
                        for (var product in products) {
                            var components = this.getComponents(products[product].templateState);
                            var maxItems = this.getMaxItems(components) || 0;
                            var rating = this.getRating(components) || 0;
                            var seller = this.getSeller(components);
                            var id = products[product].cellTrackingInfo.id;
                            var title = products[product].cellTrackingInfo.title;
                            var price = products[product].cellTrackingInfo.finalPrice;

                            promises.push(this.addRow({
                                'id': id,
                                'Category1': mainCategoryName,
                                'Category2': subCategoryName,
                                'Category3': subCategory2Name,
                                'Name': title,
                                'Price': price,
                                'Quantity': maxItems,
                                'Reviews': rating,
                                'Seller': seller
                            }, worksheet));

                           // promisesDB.push(this.setMaxItems(id, maxItems));
                            this.log("#" + numProducts + " (" + page + ") " + title + " (" + id + ")\n");
                            row++;
                            numProducts++;
                        }
                    }
                }
            }
            await Promise.all(promises).then(async (promises_res) => {
                th.clientDb.close();
                await wb.commit(); 
            });

           /* await Promise.all(promisesDB).then(() => {
                th.clientDb.close();
            })*/
        }

    }

addRow(obj, worksheet) {
        return new Promise(async (resolve, reject) => {
            var periods = ["day", "week", "month"];
            for (var period in periods) {
                obj[periods[period]] = await this.getStat(obj.id, periods[period], obj.Quantity, null, null);
            }
            worksheet.addRow(obj).commit();
            resolve(obj);
        });
    }