Express on AWS with SST - Sst

We are going to build an app with Express, add an S3 Bucket for file uploads, and deploy it to AWS in a container with SST.

:::tip[View source] You can view the source of this example in our repo. :::

Before you get started, make sure to configure your AWS credentials.

Examples

We also have a few other Express examples that you can refer to.

1. Create a project

Let's start by creating our Express app.

bash

mkdir aws-express && cd aws-express
npm init -y
npm install express

Init Express

Create your app by adding an index.mjs to the root.

import express from "express";

const PORT = 80;

const app = express();

app.get("/", (req, res) => {
  res.send("Hello World!")
});

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

Init SST

Now let's initialize SST in our app.

bash

npx sst@latest init
npm install

This'll create a sst.config.ts file in your project root.

2. Add a Service

To deploy our Express app, let's add an AWS Fargate container with Amazon ECS. Update your sst.config.ts.

async run() {
  const vpc = new sst.aws.Vpc("MyVpc");
  const cluster = new sst.aws.Cluster("MyCluster", { vpc });

  new sst.aws.Service("MyService", {
    cluster,
    loadBalancer: {
      ports: [{ listen: "80/http" }],
    },
    dev: {
      command: "node --watch index.mjs",
    },
  });
}

This creates a VPC with an ECS Cluster, and adds a Fargate service to it.

:::note By default, your service in not deployed when running in dev. :::

The dev.command tells SST to instead run our Express app locally in dev mode.

Start dev mode

Run the following to start dev mode. This'll start SST and your Express app.

bash

npx sst dev

Once complete, click on MyService in the sidebar and open your Express app in your browser.

3. Add an S3 Bucket

Let's add an S3 Bucket for file uploads. Add this to your sst.config.ts below the Vpc component.

const bucket = new sst.aws.Bucket("MyBucket");

Link the bucket

Now, link the bucket to the container.

new sst.aws.Service("MyService", {
  // ...
  link: [bucket],
});

This will allow us to reference the bucket in our Express app.

4. Upload a file

We want a POST request made to the / route to upload a file to our S3 bucket. Let's add this below our Hello World route in our index.mjs.

app.post("/", upload.single("file"), async (req, res) => {
  const file = req.file;
  const params = {
    Bucket: Resource.MyBucket.name,
    ContentType: file.mimetype,
    Key: file.originalname,
    Body: file.buffer,
  };

  const upload = new Upload({
    params,
    client: s3,
  });

  await upload.done();

  res.status(200).send("File uploaded successfully.");
});

:::tip We are directly accessing our S3 bucket with Resource.MyBucket.name. :::

Add the imports. We'll use the extra ones below.

import multer from "multer";
import { Resource } from "sst";
import { Upload } from "@aws-sdk/lib-storage";
import { getSignedUrl } from "@aws-sdk/s3-request-presigner";
import {
  S3Client,
  GetObjectCommand,
  ListObjectsV2Command,
} from "@aws-sdk/client-s3";

const s3 = new S3Client({});
const upload = multer({ storage: multer.memoryStorage() });

And install the npm packages.

bash

npm install multer @aws-sdk/client-s3 @aws-sdk/lib-storage @aws-sdk/s3-request-presigner

5. Download the file

We'll add a /latest route that'll download the latest file in our S3 bucket. Let's add this below our upload route in index.mjs.

app.get("/latest", async (req, res) => {
  const objects = await s3.send(
    new ListObjectsV2Command({
      Bucket: Resource.MyBucket.name,
    }),
  );

  const latestFile = objects.Contents.sort(
    (a, b) => b.LastModified - a.LastModified,
  )[0];

  const command = new GetObjectCommand({
    Key: latestFile.Key,
    Bucket: Resource.MyBucket.name,
  });
  const url = await getSignedUrl(s3, command);

  res.redirect(url);
});

Test your app

To upload a file run the following from your project root.

bash

curl -F [email protected] http://localhost:80/

This should upload the package.json. Now head over to http://localhost:80/latest in your browser and it'll show you what you just uploaded.

5. Deploy your app

To deploy our app we'll first add a Dockerfile.

dockerfile

FROM node:lts-alpine

WORKDIR /app/

COPY package.json /app
RUN npm install

COPY index.mjs /app

ENTRYPOINT ["node", "index.mjs"]

This just builds our Express app in a Docker image.

:::tip You need to be running Docker Desktop to deploy your app. :::

Let's also add a .dockerignore file in the root.

bash

node_modules

Now to build our Docker image and deploy we run:

bash

npx sst deploy --stage production

You can use any stage name here but it's good to create a new stage for production. This'll give the URL of your Express app deployed as a Fargate service.

bash

✓  Complete
   MyService: http://jayair-MyServiceLoadBala-592628062.us-east-1.elb.amazonaws.com

Connect the console

As a next step, you can setup the SST Console to git push to deploy your app and monitor it for any issues.

You can create a free account and connect it to your AWS account.