How to deploy a Node.js application to AWS Lambda using Serverless
By: Akira Ito
Tags: Lambda, AWS Lambda, AWS, Serverless, Nodejs

Photo by Christian Wiediger on Unsplash

What’s AWS Lambda?

AWS Lambda is a pay-as-you-go serverless compute service. Meaning what now? Well, you just deploy your source code to AWS and they handle the rest. Amazing! No need to fiddle with servers, ssh connections, Linux or Vim. But, want to know what’s even better? It scales automatically and has absolutely no downtime. I’ll let that sink in…

The technical definition for AWS Lambda would be a Function as a Service. You deploy some code, it gets invoked, processes some input, and returns a value. Simple!

Hold up a sec. We need to mention a crucial fact. All lambda functions are stateless, meaning they cannot store persistent data. And, if I just said Function as a Service, how do we deploy a whole Node.js application to AWS Lambda?

But, how does it work?

When you think about it, it’s not that complicated. A single lambda function is essentially just a tiny Node.js runtime environment. You can run whatever you want in there. That’s what we’ll do, package up a Node.js app and send it off to AWS Lambda. Sneaky. 😉

What will we deploy?

To make this example as simple as possible, the code we’ll be deploying is just 7 lines long. However, it could be as large as any Node.js application you have in production, and it would all work like a charm. Intriguing…

How do we deploy it?

In comes the Serverless Framework like a horse riding a white knight! Hold up, I may have that backward. 🤔

Anyhow, this awesome framework enables us to both develop our apps locally, just like we’re used to, but also deploy it with one simple command. Hmm… tell me more.

Let’s get coding!

First thing’s first. Open up your terminal, we need to install some packages. Yay, installing stuff, love it! 😫

1. Install and configure the Serverless Framework

$ npm install -g serverless

Note: Prefix the command with sudo if you're running this command on Linux.

$ sls config credentials --provider aws --key PUBLIC_KEY --secret SECRET_KEY

Make sure to add your IAM User’s public and secret key instead of the placeholders I specified above. If you skipped this part above, here’s the official guide in the AWS docs.

2. Create the boilerplate code

Let’s create a new folder and give it a rather noteworthy name. Jump over to your terminal and run the commands below.

$ mkdir serverless-nodejs-app && cd serverless-nodejs-app

Awesome, now what’s left is to run the create command to generate some starter code for us. This is called a serverless service.

$ sls create -t aws-nodejs -n serverless-nodejs-app

Only one more step before opening a code editor.

3. Installing dependencies

Like you can see in the code snippet above, we need to install a few modules first. Lucky for us there are only two and it’s as simple as running one command.

$ npm init -y

$ npm install --save express serverless-http

That’s it! Let’s open it up in a code editor and do some real coding.

4. Coding for real

Once you open up the code editor, you’ll see three files. Ignoring the .gitignore file, let me explain what the handler.js is first, then I'll move on to the serverless.yml . The handler will hold all your app logic, all the code. While the servereless.yml is the configuration file for the resources you'll be creating on AWS.

Go ahead and rename the handler.js to app.js , just to make it simpler for us to figure out what goes where.

Delete all the starter code and paste this code snippet into the app.js file.

// app.js



const express = require('express')

const sls = require('serverless-http')

const app = express()

app.get('/', async (req, res, next) => {

res.status(200).send('Hello World!')

})

module.exports.server = sls(app)

Seven lines of code 😎. Looks familiar right? Just like you’re used to. That’s it. Believe it or not, there’s nothing more to it. Let’s move on to the serverless.yml .

Once again, delete all the boilerplate code and paste this in.

# serverless.yml



service: serverless-nodejs-app



provider:

name: aws

runtime: nodejs8.10

stage: dev

region: eu-central-1



functions:

app:

handler: app.server # reference the file and exported method

events: # events trigger lambda functions

- http: # this is an API Gateway HTTP event trigger

path: /

method: ANY

cors: true

- http: # all routes get proxied to the Express router

path: /{proxy+}

method: ANY

cors: true

Done! All that's left is to deploy it.

Ready to deploy!

Switch back to the terminal window. By running one simple command your app will be deployed.

$ sls deploy

The Serverless Framework will now wrap everything up into a nice bundle, create a CloudFormation file from the serverless.yml and shoot it off to AWS S3. Once the resources are created and the code is deployed, you'll see an endpoint get sent back to you in the terminal.

Opening up the provided URL in a browser you’ll see Hello World! get sent back to you.

Deploying to production!

This is great and all, but not really ready for a production environment… yet. Worry not! You’ll be surprised how simple it is to make it production ready.

1. Add a secrets.json file to keep environment variables

For now, let’s just add the NODE_ENV in the secrets.json .

{

"NODE_ENV": "production"

}

2. Add a reference for the secrets.json in the serverless.yml

As simple as it was to add the secrets file, it’s even easier to just reference the file in the serverless.yml .

service: serverless-nodejs-app custom: # add these two lines

secrets: ${file(secrets.json)} # reference the secrets.json file provider:

name: aws

runtime: nodejs8.10

stage: production # make sure to change this to production

region: eu-central-1

environment: # add environment property

NODE_ENV: ${self:custom.secrets.NODE_ENV}

# reference the NODE_ENV from the secrets.json file functions:

app:

handler: app.server

events:

- http:

path: /

method: ANY

cors: true

- http:

path: /{proxy+}

method: ANY

cors: true

Amazing, that’s it! Delete the node_modules and .serverless folders from the service and run npm install once again, but this time with the --production flag.

$ npm install --production

Great! All that’s left is to re-deploy the service and you’re set.

$ sls deploy

And this is what we end up with.

I guess we’re done? Not really. Having an app running in production just because you installed npm modules with --production doesn't really cut it. To be able to sleep well at night, I need a bit more. Here's where proper system insight and monitoring tools come to play. Let me show you.

How to gain insight into your system?

The #1 problem with all serverless applications are their distributed nature. Plain and simple, it’s impossibly hard to have an overview of all the things going on. Not to mention how hard it is to debug when something goes wrong.

To calm my fears I use Dashbird. It’s a simple monitoring tool that doesn’t require me to change any code and has absolutely no overhead. So, no performance-hits either. Nice!

Thankfully, they have sensible documentation, which makes the onboarding process a breeze. Go ahead and follow their Quick Start guide. Don’t forget to come back here though. 😄

Once you’re done, all the requests will start piling in one by one and you should see something like this.

Conclusion

Lambda is awesome! When combined with HTTP event triggers such as API Gateway, development tools like the Serverless Framework and observability tools such as Dashbird, things just become so easy.

This simple API example we coded above is just a proof of concept. But you can see the point. It gives you a starting point from where you can create awesome production apps!

If you missed any of the steps above, here’s the repository with all the code.

Feel free to join my serverless newsletter if you want to play a key role in the serverless revolution!

Or, take a look at a few of my other articles regarding serverless:

Hope you guys and girls enjoyed reading this as much as I enjoyed writing it. Until next time, be curious and have fun.