Do you have the skills it takes to build modern applications that are distributed and designed for scale and agility? If you’re interested in learning to build cloud native applications and architecture practices, join us for AWS Dev Hour: Building Modern Apps, a weekly Twitch show presented by AWS Training and Certification. Built by developers for developers, the series offers a hands-on approach. Over the course of 8 episodes, AWS expert hosts Ben Newton and May Kyaw will take you through the end-to-end build of a serverless application in the AWS cloud. You’ll have the chance to learn by doing, following along with the hosts and developing a cloud-native application using the AWS free tier. You’ll learn best practices for modern applications and better understand how AWS cloud-native applications differ from on-premises. Throughout the series, you’ll receive code, white papers, links to documentation, and other resources to help you progress.

During each episode, we will be progressively building this full-stack application together. Please see the following URL for schedule and episode details:

AWS Dev Hour Schedule

• Amazon Cognito
• Amazon S3
• Amazon Simple Queue Service
• AWS Lambda
• Amazon DynamoDB
• Amazon Rekognition
• AWS Cloud Development Kit
• Amazon API Gateway
• AWS CodeBuild
• AWS CodePipeline

• npm install install packages
• cdk synth emits the synthesized CloudFormation template
• cdk deploy deploy this stack
• cdk diff compare deployed stack with current state

The cdk.json file tells the CDK Toolkit how to execute your app.

All CDK developers need to install Node.js 10.3.0 or later, even those working in languages other than TypeScript or JavaScript. The AWS CDK Toolkit (cdk command-line tool) and the AWS Construct Library run on Node.js. The bindings for other supported languages use this back end and tool set. We suggest the latest LTS version.

aws configure
npm -g install typescript
npm install -g aws-cdk

If you have not yet done so, you will also need to bootstrap your account:

cdk bootstrap aws:https://ACCOUNT-NUMBER-1/REGION-1

for example:

cdk bootstrap aws:https://123456789012/us-east-1

For further information, please see:

https://docs.aws.amazon.com/cdk/latest/guide/getting_started.html

https://docs.aws.amazon.com/cdk/latest/guide/bootstrapping.html

Our AWS Lambda function uses the Pillow library for the generation of thumbnail images. This library needs to be added into our project so that we can allow the CDK to package it and create an AWS Lambda Layer for us. To do this, you can use the following steps. (Please note, creating these resources in your AWS account could incur costs, although we have tried to select free-tier eligble resources here).

1. Launch an Amazon EC2 Instance (t2-micro) using the Amazon Linux 2 AMI
2. SSH into your instance and run the following commands:

sudo yum install -y python3-pip python3 python3-setuptools
python3 -m venv my_app/env
source ~/my_app/env/bin/activate
cd my_app/env
pip3 install pillow
cd /home/ec2-user/my_app/env/lib/python3.7/site-packages
mkdir python && cp -R ./PIL ./python && cp -R ./Pillow-8.1.0.dist-info ./python && cp -R ./Pillow.libs ./python && zip -r pillow.zip ./python

3. Copy the resulting archive 'pillow.zip' to your development environment (we used an Amazon S3 bucket for this)
4. Extract the archive into the 'reklayer' folder in your project directory

Your project structure should look something like this:

project-root/reklayer/python/PIL
project-root/reklayer/python/Pillow-8.1.0.dist-info
project-root/reklayer/python/Pillow.libs

5. Remove the python.zip file to clean up
6. Terminate the Amazon EC2 Instance that you created to build the archive

1. npm install

2. cdk deploy

A 'cdk deploy' will deploy everything that you need into your account

3. You may now test the backend by uploading an image into your Amazon S3 bucket.

To clean up the resources created by the CDK, run the following commands:

aws s3 rm --recursive s3:https://{imageBucket}
cdk destroy

(Enter “y” in response to: Are you sure you want to delete (y/n)?).

Rekognition confidence is currently set in the rekognition lambda.

minConfidence = 50

Feel free to adjust and experiment. If you change, make sure to perform another 'cdk deploy' to update the lambda function.

We would encourage all of our AWS Dev Hour viewers to contribute to this project. For more details, please refer to 'CONTRIBUTING.md'.

This software is licensed under the Apache License, Version 2.0.