Revisited Modern Application Workshop using Python CDK stacks

This is an exercise based on the AWS project Build a Modern Application on AWS (Python) with AWS-CDK.
The goal is to provide corresponding Python CDK stack files based on the original Typescript CDK stack files.
The original aws-modern-application-workshop repository provides a description of the project and a diagram of the architecture to deploy, with a number of step-by-step instructions detailed in a sequence of modules. Each module describes how to deploy the required AWS resources using the AWS CDK.

The project in this repository can deploy the complete workshop architecure in one shot using the GitHub action deploy.yml in .github/workflows. The GitHub workflow, when enabled from the Actions page, will run on every commit to the main branch. Before running the action it is necessary to create the following secrets for the GitHub repository using the Secrets section of the Settings page:

• AWS_ACCESS_KEY_ID (access key of the AWS user used to work with the AWS resources)
• AWS_SECRET_ACCESS_KEY (secret access key associated to the user)
• AWS_REGION (the desired AWS region)
• AWS_ID (the AWS account id)
• RECEIVER_EMAIL (the email that will receive the messages from the visitors of the web site)

It is also possible to do a step-by-step deployment issuing the CDK commands locally, as described in notes.txt.

NOTES

• The Python CDK stack files are located in the webgen/webgen subfolder. All the modules of the original project are covered, but this project is only available in its final state and therefore is not available as a sequence of step-by-step modules.

• In this project the CI/CD pipeline is managed using a workflow based on GitHub Actions.
  The CICD stack of the original project (based on AWS CodeCommit, CodeBuild and CodePipeline) is not used, although a cicd_stack.py file is provided as an example (currently not working).

• Please check notes.txt for details about this project before using it.

MAIN DIFFERENCES FROM THE ORIGINAL WORKSHOP

The repository organization and the deployment flow have been organized in order to facilitate a CI/CD with GitHub Actions. Here is a list of the main differences compared to the original project strucure:

• module 1
  The files in app/service have been modified: check module 3 below.
  Beyond the Python adaptation of the original stack file in web_application_stack.py, an alternative webgen_stack.py file is available which makes use of the convenient all-in-one stack CDK-SPA-Deploy for deploying a static website. Check the comments in app.py if you want to use it.

• module 2
  Beyond the network_stack.py ecr_stack.py ecs_stack.py sequence, it is also available an alternative all-in-one network_ecr_stack.py file. Check the comments in app.py if you want to use it.

• module 3
  The file populate-dynamodb.json has been moved to app/service, where mythicalMysfitsService.py and mysfitsTableClient.py have been modified to include code for loading the table upon the service startup.

• module 4
  apigateway_stack.py makes automatic use of the file api-swagger.json to create the API. api-swagger.json is located in utils/templates

• module 5
  The lambda function is in the lambda_streaming_processor folder and makes use of an environment variable

• module 6 The lambda functions are in the lambda_questions folder and the UNCOMMENT_BEFORE_2ND_DEPLOYMENT instruction has been applied

• module 7 The lambda function is in the lambda_recommendations folder.
  In sagemaker_stack.pythe code for the deployment of the SageMaker notebook has been commented out, since the deployment with the GitHub workflow makes use of a Python script to directly create the inference endpoint without human interaction (file mysfit_recommendations_knn.py).
  The script has been obtained directly from the original notebook file mysfit_recommendations_knn.ipynb using the save as .py notebook menu option.
  mysfit_recommendations_knn.py also includes some changes noted in the comments.

• Additional notes
  The GitHub workflow executes some Python scripts located in utils. When a script interacts with AWS resources, in general the AWS boto3 library is used.

  • The scripts test_ecr_empty.py and test_no_inference_endpoint provide a true/false output allowing to put a condition on the build respectively of the ECR repository and of the inference endpoint.
  • The dorny/paths-filter@v2 GitHub action provides a true/false output to flag when any changes occurred in specified paths after a commit, in order to put an additional condition on certain workflow steps to avoid unnecessary build or deployment.
  • The script prepare_files.py is used to replace the placeholders in the files where actual deployment string values are required.
  • The script deploy_ecs_service.py is used to update the ECS service under certain conditions.
  • The cleanup script clean_utils.py is not part of the GitHub workflow. It can be used to delete the remaining deployed resources AFTER a cdk destroy --all command has completed: since this script deletes resources based on names or name prefixes, use it carefully to avoid deleting resources that should be kept
  • In utils/templates there is also a copy of the web files that can be used to manually restore the original ones in the web folder: this can be useful in case the web files are overwritten by the placeholders replacement during a manual deployment.
    This situation does not occur during an automated GitHub workflow deployment because in that case the overwriting of the web files only occurs on the virtual machine used for the deployment, which is destroyed after the workflow completion.