todo-list-serverless

This project contains source code and supporting files for a todo list serverless application that is managed with the AWS Serverless Application Model (SAM) and can use the SAM CLI to deploy the application. It includes the following files and folders.

• src/ - Code for the application's Lambda functions.
• events/ - Invocation events that you can use to invoke the function.
• tests/ - Unit tests for the application code.
• template.yaml - A template that defines the application's AWS resources.

The application uses several AWS resources, including Lambda functions and an API Gateway API. These resources are defined in the template.yaml file in this project.

Project Summary

This todo list application is a web API for a todo list application. It is built using serverless technologies in complete native AWS services. This project is a bit contrived in its business requirements/features where they are specified, designed by myself.

The todo list API allows you to:

• create new todos
• get existing todo
• update existing todos
• list all todos (incl. archived ones)
• delete existing todos
• archived todos
• mark todos as done

Architecture

API Guide

This section provides in-depth guide on the APIs.

Create new Todos

To create new todos, make a post request to:

e.g.

curl -X POST -d '{"title": "todo title", "content": "the content"}' http://{todo-list-api}/todo-list/create

Get Todo

curl http://{todo-list-api}/todo-list/{item_id}

Update existing Todo

To update existing todos, make the following request:

e.g.

curl -X PUT -d '{"item_id": "e99b8e6d-40a0-11eb-8288-3be6f58d0c20", "title": "updated title", "content": "updated content"}' http://{todo-list-api}/todo-list/update

List all Todos

To fetch all the todos;

curl http://{todo-list-api}/todo-list/

Delete existing Todos

Todos are not permanently deleted. They are marked as 'deleted' with the is_deleted flag set to true.

To delete a todo you need to 'mark' it as "deleted" first by hitting the markdelete endpoint:

curl -X DELETE http://{todo-list-api}/todo-list/markdelete/{item_id}
# where item_id = the id of the todo item you want to delete

This request doesn't delete the todo but instead request for the todo to be deleted by sending a request to a backend queue (SQS) for delete processing. The delete queue triggers a mark deletion when the queue messages hit a certain threshold thereby trigger a CloudWatch Alarm which in term sends a notification to the topic (SNS Topic). A lambda subscription then triggers the actual delete lambda function to do the actual "mark deletion".

Overall, the todo stays within the DynamoDB table without ever being permanently removed. This is purely a business decision made by myself.

Archive Todos

When archiving the todo, it marks the todo item as "archived" with the is_archived flag set to true for the todo item and send a csv file equivalent of the todo to a S3 bucket that stores the archives.

curl -X POST http://{todo-list-api}/todo-list/archive/{item_id}

# where item_id is the id of the todo item

Mark Todos as Done

When marking a todo as "Done", make a request like the following:

curl -X POST http://{todo-list-api}/todo-list/complete/{item_id}

# where item_id is the id of the todo item

When 'completing' the todo we just mark it as "Complete" by setting the is_done flag of the todo item to true.

Development

If you prefer to use an integrated development environment (IDE) to build and test your application, you can use the AWS Toolkit.
The AWS Toolkit is an open source plug-in for popular IDEs that uses the SAM CLI to build and deploy serverless applications on AWS. The AWS Toolkit also adds a simplified step-through debugging experience for Lambda function code. See the following links to get started.

• PyCharm
• IntelliJ
• VS Code
• Visual Studio

Tech Stack

• SAM
• Lambda
• API Gateway
• DynamoDB
• S3
• SQS
• SNS
• X-Ray
• Systems Manager
  • Parameter Store (SSM)
• CloudWatch
  • CloudWatch Alarms

Deploy the application

The Serverless Application Model Command Line Interface (SAM CLI) is an extension of the AWS CLI that adds functionality for building and testing Lambda applications. It uses Docker to run your functions in an Amazon Linux environment that matches Lambda. It can also emulate your application's build environment and API.

To use the SAM CLI, you need the following tools.

• SAM CLI - Install the SAM CLI
• Python 3 installed
• Docker - Install Docker community edition

To build and deploy your application for the first time, run the following in your shell:

sam build --use-container
sam deploy --guided

The first command will build the source of your application. The second command will package and deploy your application to AWS, with a series of prompts:

• Stack Name: The name of the stack to deploy to CloudFormation. This should be unique to your account and region, and a good starting point would be something matching your project name.
• AWS Region: The AWS region you want to deploy your app to.
• Confirm changes before deploy: If set to yes, any change sets will be shown to you before execution for manual review. If set to no, the AWS SAM CLI will automatically deploy application changes.
• Allow SAM CLI IAM role creation: Many AWS SAM templates, including this example, create AWS IAM roles required for the AWS Lambda function(s) included to access AWS services. By default, these are scoped down to minimum required permissions. To deploy an AWS CloudFormation stack which creates or modified IAM roles, the CAPABILITY_IAM value for capabilities must be provided. If permission isn't provided through this prompt, to deploy this example you must explicitly pass --capabilities CAPABILITY_IAM to the sam deploy command.
• Save arguments to samconfig.toml: If set to yes, your choices will be saved to a configuration file inside the project, so that in the future you can just re-run sam deploy without parameters to deploy changes to your application.

You can find your API Gateway Endpoint URL in the output values displayed after deployment.

Use the SAM CLI to build and test locally

Build your application with the sam build --use-container command.

todo-list-serverless$ sam build --use-container

The SAM CLI installs dependencies defined in hello_world/requirements.txt, creates a deployment package, and saves it in the .aws-sam/build folder.

Test a single function by invoking it directly with a test event. An event is a JSON document that represents the input that the function receives from the event source. Test events are included in the events folder in this project.

Run functions locally and invoke them with the sam local invoke command.

todo-list-serverless$ sam local invoke HelloWorldFunction --event events/event.json

The SAM CLI can also emulate your application's API. Use the sam local start-api to run the API locally on port 3000.

todo-list-serverless$ sam local start-api
todo-list-serverless$ curl http://localhost:3000/

The SAM CLI reads the application template to determine the API's routes and the functions that they invoke. The Events property on each function's definition includes the route and method for each path.

      Events:
        HelloWorld:
          Type: Api
          Properties:
            Path: /hello
            Method: get

Add a resource to your application

The application template uses AWS Serverless Application Model (AWS SAM) to define application resources. AWS SAM is an extension of AWS CloudFormation with a simpler syntax for configuring common serverless application resources such as functions, triggers, and APIs. For resources not included in the SAM specification, you can use standard AWS CloudFormation resource types.

Fetch, tail, and filter Lambda function logs

To simplify troubleshooting, SAM CLI has a command called sam logs. sam logs lets you fetch logs generated by your deployed Lambda function from the command line. In addition to printing the logs on the terminal, this command has several nifty features to help you quickly find the bug.

NOTE: This command works for all AWS Lambda functions; not just the ones you deploy using SAM.

todo-list-serverless$ sam logs -n HelloWorldFunction --stack-name todo-list-serverless --tail

You can find more information and examples about filtering Lambda function logs in the SAM CLI Documentation.

Unit tests

Tests are defined in the tests folder in this project. Use PIP to install the pytest and run unit tests.

todo-list-serverless$ pip install pytest pytest-mock --user
todo-list-serverless$ python -m pytest tests/ -v

Cleanup

To delete the sample application that you created, use the AWS CLI. Assuming you used your project name for the stack name, you can run the following:

aws cloudformation delete-stack --stack-name todo-list-serverless

Resources

See the AWS SAM developer guide for an introduction to SAM specification, the SAM CLI, and serverless application concepts.

Next, you can use AWS Serverless Application Repository to deploy ready to use Apps that go beyond hello world samples and learn how authors developed their applications: AWS Serverless Application Repository main page