How to Wait Until a MongoDB Connection is Made before Using the Database

Question

I have the following code to create a connection to my MongoDB database, and to store it for future use.

const mongodb = require('mongodb');
const MongoClient = mongodb.MongoClient;

// The database will be defined once a connection to between the cluster and mongodb is created
let _database;

const uri = '';
const databaseName = 'db';

const mongoConnect = () => {
    MongoClient.connect(uri)
        .then((client) => {
            _database = client.db(databaseName);
        })
        .catch((err) => {
            console.log(err);
            throw err;
        });
};

const getDb = () => {
    if (_database) {
        return _database;
    }
    throw 'No database found!';
};

module.exports = {
    mongoConnect,
    getDb
}

My problem is that _database is undefined until the connection is made. If my website tries to use the database before _database is defined it will throw an error and crash.

I want to make it so instead of crashing, other portions of my code would just wait until _database is not undefined. Sounds like a await/async solution is needed, but I can't wrap my head around how to approach implementing something like that here. Any advice would be great!

Answer 1

**Pretty Simple approach ** Just add await before MongoClient.connect function and make function async Now It will wait for the connection to have response then move forward.

const mongodb = require('mongodb');
const MongoClient = mongodb.MongoClient;

// The database will be defined once a connection to between the cluster 
and mongodb is created
let _database;

const uri = 'mongodb://localhost:27017/mydb';
const databaseName = 'db';

const mongoConnect = async () => {
await MongoClient.connect(uri)
    .then((client) => {
        _database = client.db(databaseName);
    })
    .catch((err) => {
        console.log(err);
        throw err;
    });
 };

const getDb = () => { 
  if (_database) {
    return _database;
}
throw 'No database found!'; 
};



module.exports = {
  mongoConnect,
  getDb
}

Answer 2

Embedding AWS credentials on any client-side apps is a scary idea. In order to solve this challenge, you would have to use either CloudFront or S3 Signed URLs.

This approach requires the generation of short-lived upload/download URLs in one of your APIs so that it could send back to the client-application a URL where we can directly upload/download assets to/from an S3 bucket.

It allows us to avoid the hardcoding of AWS credentials on client-applications and have dynamic short-lived URLs dedicated for one-time upload/download operations on-demand.

It shouldn't be that hard and you could follow this tutorial to learn more about S3 signed urls.