[AWS CDK] CDK Structure

Explore your project directory

You’ll see something like this:

• lib/cdk-workshop-stack.ts is where your CDK application’s main stack is defined. This is the file we’ll be spending most of our time in.
• bin/cdk-workshop.ts is the entrypoint of the CDK application. It will load the stack defined in lib/cdk-workshop-stack.ts.
• package.json is your npm module manifest. It includes information like the name of your app, version, dependencies and build scripts like “watch” and “build” (package-lock.json is maintained by npm)
• cdk.json tells the toolkit how to run your app. In our case it will be "npx ts-node bin/cdk-workshop.ts"
• tsconfig.json your project’s typescript configuration
• .gitignore and .npmignore tell git and npm which files to include/exclude from source control and when publishing this module to the package manager.
• node_modules is maintained by npm and includes all your project’s dependencies.

Your app’s entry point

Let’s have a quick look at bin/cdk-workshop.ts:

#!/usr/bin/env node
import * as cdk from 'aws-cdk-lib';
import { CdkWorkshopStack } from '../lib/cdk-workshop-stack';

const app = new cdk.App();
new CdkWorkshopStack(app, 'CdkWorkshopStack');

This code loads and instantiates the CdkWorkshopStack class from the lib/cdk-workshop-stack.ts file. We won’t need to look at this file anymore.

The main stack

Open up lib/cdk-workshop-stack.ts. This is where the meat of our application is:

import * as cdk from 'aws-cdk-lib';
import * as sns from 'aws-cdk-lib/aws-sns';
import * as subs from 'aws-cdk-lib/aws-sns-subscriptions';
import * as sqs from 'aws-cdk-lib/aws-sqs';

export class CdkWorkshopStack extends cdk.Stack {
  constructor(scope: cdk.App, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    const queue = new sqs.Queue(this, 'CdkWorkshopQueue', {
      visibilityTimeout: cdk.Duration.seconds(300)
    });

    const topic = new sns.Topic(this, 'CdkWorkshopTopic');

    topic.addSubscription(new subs.SqsSubscription(queue));
  }
}

As you can see, our app was created with a sample CDK stack (CdkWorkshopStack).

The stack includes:

• SQS Queue (new sqs.Queue)
• SNS Topic (new sns.Topic)
• Subscribes the queue to receive any messages published to the topic (topic.addSubscription)