Open your IDE #

Now’s a good time to open the project in your favorite IDE and explore.

If you use VSCode, you can just type code . within the project directory.

Explore your project directory #

You’ll see something like this:

• .venv - The python virtual environment information discussed in the previous section.
• cdk_workshop — A Python module directory.
  • cdk_workshop.egg-info - Folder that contains build information relevant for the packaging on the project
  • cdk_workshop_stack.py—A custom CDK stack construct for use in your CDK application.
• tests — Contains all tests.
  • unit — Contains unit tests.
    • test_cdk_workshop.py—A trivial test of the custom CDK stack created in the cdk_workshop package. This is mainly to demonstrate how tests can be hooked up to the project.
• app.py — The “main” for this sample application.
• cdk.json — A configuration file for CDK that defines what executable CDK should run to generate the CDK construct tree.
• README.md — The introductory README for this project.
• requirements.txt—This file is used by pip to install all of the dependencies for your application.

Your app’s entry point #

Let’s have a quick look at app.py:

#!/usr/bin/env python3

import aws_cdk as cdk

from cdk_workshop.cdk_workshop_stack import CdkWorkshopStack


app = cdk.App()
CdkWorkshopStack(app, "cdk-workshop")

app.synth()

This code loads and instantiates an instance of the CdkWorkshopStack class from cdk_workshop/cdk_workshop_stack.py file. We won’t need to look at this file anymore.

The main stack #

Open up cdk_workshop/cdk_workshop_stack.py. This is where the meat of our application is:

from constructs import Construct
from aws_cdk import (
    Duration,
    Stack,
    aws_sqs as sqs,
    aws_sns as sns,
    aws_sns_subscriptions as subs,
)

class CdkWorkshopStack(Stack):

    def __init__(self, scope: Construct, id: str, **kwargs) -> None:
        super().__init__(scope, id, **kwargs)

        queue = sqs.Queue(
            self, "CdkWorkshopQueue",
            visibility_timeout=Duration.seconds(300),
        )

        topic = sns.Topic(
            self, "CdkWorkshopTopic"
        )

        topic.add_subscription(subs.SqsSubscription(queue))

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

The stack includes:

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