In this example we will look at how to use SQS to create a queue in our serverless app using SST. We’ll be creating a simple queue system.

Requirements

Create an SST app

Change indicator Let’s start by creating an SST app.

$ npx create-sst@latest --template=base/example queue
$ cd queue
$ npm install

By default, our app will be deployed to the us-east-1 AWS region. This can be changed in the sst.config.ts in your project root.

import { SSTConfig } from "sst";

export default {
  config(_input) {
    return {
      name: "queue",
      region: "us-east-1",
    };
  },
} satisfies SSTConfig;

Project layout

An SST app is made up of two parts.

  1. stacks/ — App Infrastructure

    The code that describes the infrastructure of your serverless app is placed in the stacks/ directory of your project. SST uses AWS CDK, to create the infrastructure.

  2. packages/functions/ — App Code

    The code that’s run when your API is invoked is placed in the packages/functions/ directory of your project.

Adding SQS Queue

Amazon SQS is a reliable and high-throughput message queuing service. You are charged based on the number of API requests made to SQS. And you won’t get charged if you are not using it.

Change indicator Replace the stacks/ExampleStack.ts with the following.

import { StackContext, Queue, Api } from "sst/constructs";

export function ExampleStack({ stack }: StackContext) {
  // Create Queue
  const queue = new Queue(stack, "Queue", {
    consumer: "packages/functions/src/consumer.main",
  });
}

This creates an SQS queue using Queue. And it has a consumer that polls for messages from the queue. The consumer function will run when it has polled 1 or more messages.

Setting up the API

Now let’s add the API.

Change indicator Add this below the Queue definition in stacks/ExampleStack.ts.

// Create the HTTP API
const api = new Api(stack, "Api", {
  defaults: {
    function: {
      // Bind the table name to our API
      bind: [queue],
    },
  },
  routes: {
    "POST /": "packages/functions/src/lambda.main",
  },
});

// Show the API endpoint in the output
stack.addOutputs({
  ApiEndpoint: api.url,
});

Our API simply has one endpoint (the root). When we make a POST request to this endpoint the Lambda function called main in packages/functions/src/lambda.ts will get invoked.

We’ll also bind our queue to our API.

Adding function code

We will create two functions, one for handling the API request, and one for the consumer.

Change indicator Replace the packages/functions/src/lambda.ts with the following.

export async function main() {
  console.log("Message queued!");
  return {
    statusCode: 200,
    body: JSON.stringify({ status: "successful" }),
  };
}

Change indicator Add a packages/functions/src/consumer.ts.

import { SQSEvent } from "aws-lambda";

export async function main(event: SQSEvent) {
  const records: any[] = event.Records;
  console.log(`Message processed: "${records[0].body}"`);

  return {};
}

Now let’s test our new API.

Starting your dev environment

Change indicator SST features a Live Lambda Development environment that allows you to work on your serverless apps live.

$ npm run dev

The first time you run this command it’ll take a couple of minutes to deploy your app and a debug stack to power the Live Lambda Development environment.

Deployed:
ExampleStack
ApiEndpoint: https://3vi820odbc.execute-api.us-east-1.amazonaws.com

The ApiEndpoint is the API we just created.

Let’s test our endpoint. Run the following in a new terminal.

$ curl -X POST https://3vi820odbc.execute-api.us-east-1.amazonaws.com

This makes a POST request to our API. You should see Message queued! in the sst dev terminal.

Sending message to our queue

Now let’s send a message to our queue.

Change indicator Replace the packages/functions/src/lambda.ts with the following.

import AWS from "aws-sdk";
import { Queue } from "sst/node/queue";

const sqs = new AWS.SQS();

export async function main() {
  // Send a message to queue
  await sqs
    .sendMessage({
      // Get the queue url from the environment variable
      QueueUrl: Queue.Queue.queueUrl,
      MessageBody: JSON.stringify({ ordered: true }),
    })
    .promise();

  console.log("Message queued!");

  return {
    statusCode: 200,
    body: JSON.stringify({ status: "successful" }),
  };
}

Here we are getting the queue url from the environment variable, and then sending a message to it.

Change indicator Let’s install the aws-sdk package in the packages/functions/ folder.

$ npm install aws-sdk

Now if you hit our API again.

$ curl -X POST https://3vi820odbc.execute-api.us-east-1.amazonaws.com

You should see Message processed: "{"ordered":true}" printed out in the sst dev terminal.

Deploying to prod

Change indicator To wrap things up we’ll deploy our app to prod.

$ npx sst deploy --stage prod

This allows us to separate our environments, so when we are working in dev, it doesn’t break the API for our users.

Cleaning up

Finally, you can remove the resources created in this example using the following commands.

$ npx sst remove
$ npx sst remove --stage prod

Conclusion

And that’s it! We’ve got a completely serverless queue system. Check out the repo below for the code we used in this example. And leave a comment if you have any questions!