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AWS Lambda Handler Cookbook (Python)

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This project provides a working, open source based, AWS Lambda handler skeleton Python code including DEPLOYMENT code with CDK and a pipeline.

This project can serve as a template for new Serverless services - CDK deployment code, pipeline and handler are covered.

📜Documentation | Blogs website

Contact details | ran.isenberg@ranthebuilder.cloud

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Getting Started

You can start with a clean service out of this template repository without using the 'Template' button on GitHub.

You can use Cookiecutter.

  • Cookiecutter - install with pip/brew brew install cookiecutter or ``pip install cookiecutter`

Then run:

cookiecutter gh:ran-isenberg/cookiecutter-serverless-python

Answer the questions to select repo name, service name, etc.:

logo

That's it, your developer environment has been set! you are ready to deploy the service:

cd {new repo folder}
poetry shell
make deploy

You can also run 'make pr' will run all checks, synth, file formatters , unit tests, deploy to AWS and run integration and E2E tests.

The Problem

Starting a Serverless service can be overwhelming. You need to figure out many questions and challenges that have nothing to do with your business domain:

  • How to deploy to the cloud? What IAC framework do you choose?
  • How to write a SaaS-oriented CI/CD pipeline? What does it need to contain?
  • How do you handle observability, logging, tracing, metrics?
  • How do you write a Lambda function?
  • How do you handle testing?
  • What makes an AWS Lambda handler resilient, traceable, and easy to maintain? How do you write such a code?

The Solution

This project aims to reduce cognitive load and answer these questions for you by providing a skeleton Python Serverless service template that implements best practices for AWS Lambda, Serverless CI/CD, and AWS CDK in one template project.

Concepts

I spoke at AWS re:invent 2023 with Heitor Lessa, Chief Architect of Powertools for AWS Lambda about the concepts I implemented in this project.

Watch the video

Serverless Service - The Order service

  • This project provides a working orders service where customers can create orders of items.

  • The project deploys an API GW with an AWS Lambda integration under the path POST /api/orders/ and stores data in a DynamoDB table.

design

Monitoring Design

monitoring_design

Features

  • Python Serverless service with a recommended file structure.
  • CDK infrastructure with infrastructure tests and security tests.
  • CI/CD pipelines based on Github actions that deploys to AWS with python linters, complexity checks and style formatters.
  • CI/CD pipeline deploys to dev/staging and production environments with different gates between each environment
  • Makefile for simple developer experience.
  • The AWS Lambda handler embodies Serverless best practices and has all the bells and whistles for a proper production ready handler.
  • AWS Lambda handler uses AWS Lambda Powertools.
  • AWS Lambda handler 3 layer architecture: handler layer, logic layer and data access layer
  • Features flags and configuration based on AWS AppConfig
  • Idempotent API
  • REST API protected by WAF with four AWS managed rules in production deployment
  • CloudWatch dashboards - High level and low level including CloudWatch alarms
  • Unit, infrastructure, security, integration and end to end tests.
  • Automatically generated OpenAPI endpoint: /swagger with Pydantic schemas for both requests and responses
  • CI swagger protection - fails the PR if your swagger JSON file (stored at docs/swagger/openapi.json) is out of date
  • Automated protection against API breaking changes

CDK Deployment

The CDK code create an API GW with a path of /api/orders which triggers the lambda on 'POST' requests.

The AWS Lambda handler uses a Lambda layer optimization which takes all the packages under the [packages] section in the Pipfile and downloads them in via a Docker instance.

This allows you to package any custom dependencies you might have, just add them to the Pipfile under the [packages] section.

Serverless Best Practices

The AWS Lambda handler will implement multiple best practice utilities.

Each utility is implemented when a new blog post is published about that utility.

The utilities cover multiple aspect of a production-ready service, including:

Getting started

Head over to the complete project documentation pages at GitHub pages at https://ran-isenberg.github.io/aws-lambda-handler-cookbook

Code Contributions

Code contributions are welcomed. Read this guide.

Code of Conduct

Read our code of conduct here.

Connect

Credits

License

This library is licensed under the MIT License. See the LICENSE file.