AWS Lambda – Nodejs, Serverless

Express JS in AWS Lambda

This is a boiler plate code to deploy Express in AWS Lambda using Serverless JS. Using this you can built Express APIs in your local machine and deploy them in AWS lambda with just few commands.

Run the local.js file to test the application locally

npm install
npm start

About the files and folders

# lambda.js - File which is called by AWS lambda
# local.js - Run the app on localhost.
# src/app.js - Your App logic
# serverless.yml - Lambda function configration.

How to use

1. Both the lambda.js and local.js calls the express app in the src/app.js
2. Write your business logic (Express API) inside the src folder
3. npm start runs the local.js file to test the app in your local machine
4. serverless.yml file contains your details about your AWS region and name of your Lambda function, they are self-explanatory edit them to your needs
5. Leave the lambda.js an local.js file alone unless you know what you are doing

Prerequisites for Deploying in AWS

# An AWS account
# AWS CLI installed in your machine

AWS Configrations

Download and install AWS CLI. After installing run the following command in the terminal to configure your AWS account.

aws configure

it will ask for Access Key and Secret key, you can find them in your AWS online console.

Deployment

Run the following command to deploy the app as AWS Lambda function

npm run deploy

## After deployment

# Go to your AWS console and choose Lambda from Services.
# You can find your deployed function in list.
# Find the URL to invoke your function in the API endpoint.
# Your endpoint URL should look something like this

https://abcd123.execute-api.us-east-1.amazonaws.com/production/{proxy+}

##Invoke your function omit the ‘ {proxy+} ‘ and use the rest of the URL to call the function

https://abcd123.execute-api.us-east-1.amazonaws.com/production/

The above URL outputs the responce in app.get(‘/’, (req, res) => {}) in the app.js file

src/app.js

const express = require('express');
const app = express();

app.use(express.json());
app.use(express.urlencoded({extended:false}))

//GET
app.get('/', (req, res) => {
   res.status(200).send('hello world!');
});

//GET req Simply sends the current time
app.get('/time', (req, res) => {
   let timeNow = Date(Date.now());
   res.status(200).send(timeNow.toString());
});

//POST req logs the name and sends it
//To check send a POST req with "name" and check your lambda function console
app.post('/logthis', (req, res) => {
   const name = req.body.name;
   const toLog = `\n --- My name is ${name} -- \n`
   console.info(toLog)
   res.status(200).send(toLog);
});

module.exports = app;

lambda.js

'use strict'
//This file is AWS Lambda entry point
//All your business code (ExpressJS App) should be done in src/app.js

const awsServerlessExpress = require('aws-serverless-express');
const app = require('./src/app.js');
const server = awsServerlessExpress.createServer(app)

module.exports.handler = (event, context) => awsServerlessExpress.proxy(server, event, context);

local.js

const app = require('./src/app.js');
const port = process.env.PORT || 8000;

// Server
app.listen(port, () => {
   console.log(`Listening on: http://localhost:${port}`);
});

package.json

{
  "name": "express_in_aws",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "start": "node local.js",
    "deploy": "serverless deploy"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "aws-serverless-express": "^3.3.6",
    "express": "^4.17.1"
  },
  "devDependencies": {
    "serverless": "^1.50.1"
  }
}

serverless.yml

service: expressInAWSDemo #Name of your App

provider:
 name: aws
 runtime: nodejs10.x # Node JS version
 memorySize: 512
 timeout: 15
 stage: production
 region: us-east-1 # AWS region

functions:
 api:
   handler: lambda.handler
   events:
     - http: ANY {proxy+}
     - http: ANY /