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aws-lambda-sam-application

This project contains Python source code and supporting files for a serverless application that you can deploy with the SAM CLI.

It tries to follow best practices:

  • CodeDeploy and Lambda traffic shifting for deployment. More info
  • Authorization with Cognito.
  • Offline and local testing (WIP)
  • Regional Custom domain name.
  • AWS Lambda powertools for python More Info
  • AWS DynamoDB local More Info

This project includes the following files and folders.

  • application - Code for the application's Lambda functions (echo, get, and post).

  • pre-traffic-hook - Code for the pretraffic hook used by CodeDeploy to monitor the deployment of new Lambda functions versions. More info

  • 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.

  • scripts - Support for creating the Cognito user pool and get TokenIDs for Auth. Original source

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

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.

To build and deploy your application for the first time, run the following in your shell (change the parameters to reflect your own)

> sam build --use-container
> sam deploy --guided --parameter-overrides ParameterKey=YourEmail,ParameterValue="[email protected]" ParameterKey=DomainName,ParameterValue="sam.example.com" ParameterKey=CertificateArn,ParameterValue="arn:aws:acm:eu-west-1:12345678920:certificate/27857f5c-8bfa-45db-aaa1-00fc5302c65f"

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.
> sam deploy --parameter-overrides ParameterKey=YourEmail,ParameterValue="[email protected]" ParameterKey=DomainName,ParameterValue="sam.example.com" ParameterKey=CertificateArn,ParameterValue="arn:aws:acm:eu-west-1:12345678920:certificate/27857f5c-8bfa-45db-aaa1-00fc5302c65f"

One of the parameter, YourEmail, is used to setup a Cognito user with a default password that must be changed. That password was sent to you to the YourEmail address. To change the password to 'Testing1' (feel free to mondify the script to create a stronger password). These scripts originate from here

> sh scripts/login_first.sh {{User Pool ID}} {{User Pool Client ID}} {{Your Email}} {{Temp password that was sent to you}}

IMPORTANT

Notice the example application uses a Custom Domain Name. Thus, you will have to create a record in your DNS provider to point your domain name to the target API Gateway domain name. It looks something like that "d-he43n343n2.execute-api.eu-west-1.amazonaws.com". You can get it from the API Gateway console and looking at the custom domain name created. However, you can, of course, test everything using the standard API gateway endpoint.

Testing the application

The application supports non-auth API and Auth API, but by default, all APIs require Auth. Demos using httpie

APIs needs Authorization or you will get and Unauthorized notice.

> http https://sam.example.com/echo

{
    "message": "Unauthorized"
}

We can login using the AWS CLI to retrieve a "IdToken" to our request in order to call our API.

> cd script
> sh login.sh {{UserPool Client ID}} {{Your Email}} "Testing1"

Copy the IdToken part and use it in the Authorization header.

> http https://sam.example.com/echo Authorization:<IdToken>

{
    "message": "Hello, Worlds!"
}

> http post https://sam.example.com/create Authorization:<IdToken> name=barfoo [email protected]

{
    "email": "[email protected]",
    "id": "4a695240-5572-4ba8-bb7b-d13106bae674",
    "name": "barfoo"
}
> http https://sam.example.com/get/4a695240-5572-4ba8-bb7b-d13106bae674 Authorization:<IdToken>

{
    "id": "4a695240-5572-4ba8-bb7b-d13106bae674",
    "name": "barfoo",
    "email": "[email protected]",
    "retrieved from": "eu-west-1"
}

Use the SAM CLI to build and test locally

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

> sam build --use-container

The SAM CLI installs dependencies defined in application/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.

> sam local invoke Echo --event events/event.json

Test with DynamoDB local

Create a docker network

> docker network create sam-demo

Run DynamoDB Local

> docker run -d -v "$PWD":/dynamodb_local_db -p 8000:8000 --network sam-demo --name dynamodb cnadiminti/dynamodb-local

Bootstrap DynamoDB Local (create a database and fake data)

> python bootstrap_dynamodb.py -t "newdb" --hash-key "id"

Let SAM local plays nicely with Docker network

> sam local start-api --docker-network sam-demo

Test API locally (using httpie)

> http http://127.0.0.1:3000/echo

{
    "message": "Hello, Worlds!"
}


> http post http://127.0.0.1:3000/create name=barfoo [email protected]

{
    "email": "[email protected]",
    "id": "4a695240-5572-4ba8-bb7b-d13106bae674",
    "name": "barfoo"
}


> http http://127.0.0.1:3000/get/4a695240-5572-4ba8-bb7b-d13106bae674

{
    "email": "[email protected]",
    "id": "4a695240-5572-4ba8-bb7b-d13106bae674",
    "name": "barfoo",
    "retrieved from": "dynamodb-local"
}

Fetch, tail, and filter Lambda function logs

SAM CLI has a command called sam logs that lets you fetch logs generated by your deployed Lambda function from the command line.

> sam logs -n Echo --stack-name sam-app1 --tail

Unit tests

Tests are defined in the tests folder. Use PIP to install the pytest and run unit tests. Notice the testing happens offline with tracing disabled.

> pip install pytest pytest-mock --user
> python -m pytest tests/ -v

Cleanup

To delete the application, 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 sam-app1