Build Stateful Applications with AWS App Runner and Serverless Redis

AWS App Runner is a container service where AWS runs and scales your container in a serverless way. The container storage is ephemeral so you should keep the state in an external data store. In this tutorial we will build a simple application which will keep the state on Redis and deploy the application to AWS App Runner.

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The Stack

• Serverless compute: AWS App Runner (Node.js)
• Serverless data store: Redis via Upstash
• Deployment source: github repo

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Project Setup

Create a directory for your project:

mkdir app_runner_example

cd app_runner_example

Create a node project and install dependencies:

npm init

npm install ioredis

Create a Redis DB from Upstash. In the database details page, copy the connection code (Node tab).

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The Code

In your node project folder, create server.js and copy the below code:

var Redis = require("ioredis");
const http = require("http");

if (typeof client === "undefined") {
  var client = new Redis(process.env.REDIS_URL);
}

const requestListener = async function (req, res) {
  if (req.url !== "/favicon.ico") {
    let count = await client.incr("counter");
    res.writeHead(200);
    res.end("Page view:" + count);
  }
};

const server = http.createServer(requestListener);
server.listen(8080);

As you see, the code simple increment a counter on Redis and returns the response as the page view count.

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Deployment

You have two options to deploy your code to the App Runner. You can either share your Github repo with AWS or register your docker image to ECR. In this tutorial, we will share our Github repo with App Runner.

Create a github repo for your project and push your code. In AWS console open the App Runner service. Click on Create Service button. Select Source code repository option and add your repository by connecting your Github and AWS accounts.

In the next page, choose Nodejs 12 as your runtime, npm install as your build command, node server as your start command and 8080 as your port.

The next page configures your App Runner service. Set a name for your service. Set your Redis URL that you copied from Upstash console as REDIS_URL environment variable. Your Redis URL should be something like this: rediss://:d34baef614b6fsdeb01b25@us1-lasting-panther-33618.upstash.io:33618 You can leave other settings as default.

Click on Create and Deploy at the next page. Your service will be ready in a few minutes. Click on the default domain, you should see the page with a view counter as here.

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App Runner vs AWS Lambda

• AWS Lambda runs functions, App Runner runs applications. So with App Runner you do not need to split your application to functions.
• App Runner is a more portable solution. You can move your application from App Runner to any other container service.
• AWS Lambda price scales to zero, App Runner’s does not. With App Runner you need to pay for an at least one instance unless you pause the system.

App Runner is great alternative when you need more control on your serverless runtime and application. Check out this video to learn more about App Runner.