Connecting MongoDB from AWS Lambda and Node JS

Node.js can be used in database applications. One of the most popular NoSQL databases is MongoDB.

MongoDB

To be able to experiment with the code examples, you will need access to a MongoDB database.

You can download a free MongoDB database at https://www.mongodb.com.

Or get started right away with a MongoDB cloud service at https://www.mongodb.com/cloud/atlas.

Let us try to access a MongoDB database with Node.js.

To download and install the official MongoDB driver, open the Command Terminal and execute the following:

npm install mongodb

Node.js can use this module to manipulate MongoDB databases:
To create a database in MongoDB, start by creating a MongoClient object, then specify a connection URL with the correct IP address and the name of the database you want to create.

MongoDB will create the database if it does not exist, and make a connection to it.

var url = "mongodb://localhost:27017/lambdatest";

MongoClient.connect(url, function(err, db) {
  if (err) throw err;
  console.log("Database created!");
  db.close();
});

Now create lambda and paste the following code into it.

"use strict";
const MongoClient = require('mongodb').MongoClient;
const MONGODB_URI = process.env.MONGODB_URI; // or Atlas connection string
let cachedDb = null;
function connectToDatabase (uri) {
  console.log('=> connect to database');
if (cachedDb) {
    console.log('=> using cached database instance');
    return Promise.resolve(cachedDb);
  }
return MongoClient.connect(uri)
    .then(db => {
      cachedDb = db;
      return cachedDb;
    });
}
function queryDatabase (db) {
  console.log('=> query database');
return db.collection('items').find({}).toArray()
    .then(() => { return { statusCode: 200, body: 'success' }; })
    .catch(err => {
      console.log('=> an error occurred: ', err);
      return { statusCode: 500, body: 'error' };
    });
}
module.exports.handler = (event, context, callback) => {
  context.callbackWaitsForEmptyEventLoop = false;
console.log('event: ', event);
connectToDatabase(MONGODB_URI)
    .then(db => queryDatabase(db))
    .then(result => {
      console.log('=> returning result: ', result);
      callback(null, result);
    })
    .catch(err => {
      console.log('=> an error occurred: ', err);
      callback(err);
    });
};

Deploy your lambda function and give a try.