MongoClient possible memory leak

create.ts

import faker from 'faker';
import mongo from './mongo';

const [collectionName = 'items', size = 1] = process.argv.slice(2);

(async function create() {
  const db = await mongo();
  if (!db) {
    throw new Error('No database connection');
  }

  // eslint-disable-next-line @typescript-eslint/no-explicit-any
  const items: any[] = [];
  for (let i = 0; i < size; i += 1) {
    items.push({
      type: faker.random.arrayElement(['Admin', 'User', 'SuperUser', 'Editor', 'Viewer', 'Guest']),
      currency: faker.finance.currencyCode(),
      address: faker.address.streetAddress(),
      postalCode: faker.address.zipCode(),
      city: faker.address.city(),
      country: faker.address.country(),
      amount: faker.random.number(1000),
      email: faker.internet.email,
      name: faker.name.firstName() + ' ' + faker.name.lastName(),
      userAgent: faker.internet.userAgent(),
      phone: faker.phone.phoneNumber(),
      created: faker.date.past(),
      company: faker.company.companyName(),
      title: faker.name.jobTitle(),
    });
  }

  const collection = db.collection(collectionName);
  await collection.insertMany(items);
  // eslint-disable-next-line no-console
  console.log(`Inserted ${items.length} items`);

  process.exit();
})();

mongo.ts

import { MongoClient, Db } from 'mongodb';

const { MONGODB_URI } = process.env;

if (!MONGODB_URI) {
  // eslint-disable-next-line no-console
  console.error('MONGODB_URI is not set!');
  process.exit();
}

const databases: { [key: string]: Db } = {};
const connect = (name: string, uri?: string): Promise<Db | void> => {
  if (!uri) {
    return Promise.resolve();
  }

  const url = new URL(uri);
  const mongoDbName = url.pathname.split('/')[1];
  const mongoDbUri = url.href.substr(0, url.href.length - url.pathname.length);

  if (databases[uri]) {
    return Promise.resolve(databases[uri]);
  }

  return new Promise((resolve, reject) => {
    MongoClient.connect(
      mongoDbUri,
      { useUnifiedTopology: true },
      (error, _client) => {
        if (error) {
          reject(error);
        }

        databases[uri] = _client.db(mongoDbName);
        resolve(databases[uri]);
      }
    );
  });
};

const mongo = (): Promise<Db | void> => {
  return connect('MongoDB', MONGODB_URI);
};

export default mongo;

populate.ts

import mongo from './mongo';

const [collectionName = 'items'] = process.argv.slice(2);

(async function create() {
  const db = await mongo();
  if (!db) {
    throw new Error('No database connection');
  }

  if (db && collectionName) {
    const collection = db.collection(collectionName);
    collection.createIndex({ type: 1, created: 1 });

    // eslint-disable-next-line no-console
    console.log(`email;name;country`);
    const projection = { _id: 0, email: 1, name: 1, country: 1 };

    const types: string[] = await collection.distinct({ type }).sort();
    // eslint-disable-next-line no-restricted-syntax
    for (const type of types) {
      const query = { type: { $eq: type };
      const items = await collection.find(query, { projection }).sort({ created: 1 }).toArray();
      // eslint-disable-next-line no-restricted-syntax
      for (const item of items) {
        // eslint-disable-next-line no-console
        console.log(`${item.email}\t${item.name}\t${item.country}`);
      }
    }
    // @TODO rest of the test case to prove there's memory leak
  }

  process.exit();
})();