const mongodb = require("mongodb");

const host = "";
const dbName = "";
const collectionName = "";
const user = "";
const pass = "";

const connectionString = `mongodb://${host}`;

const config = {
  auth: {
    user: user,
    password: pass,
  },
  authSource: dbName,
  useNewUrlParser: true,
  poolSize: 10,
};

const unifiedConfig = {
  useUnifiedTopology: true,
  serverSelectionTimeoutMS: 5000, // for testing
};

async function main() {
  const client = new mongodb.MongoClient(connectionString, {
    ...config,
    ...unifiedConfig,
  });

  const pool = await client.connect();
  const db = pool.db(dbName);

  while (true) {
    try {
      const cursor = db.collection(collectionName).find({});

      // Got stuck here until connection is restored
      // or process shuts down without error after a few reconnection attempts
      const result = await cursor.toArray();

      console.debug(JSON.stringify(result));
    } catch (error) {
      console.error(error.message);
    }
    await delay(1000);
  }

  // await pool.close();
}

try {
  main();
} catch (error) {
  console.error(error);
}

async function delay(timeout) {
  return new Promise((resolve, _reject) => {
    setTimeout(() => {
      resolve();
    }, timeout);
  });
}