# Random A/B testing at the edge using Amazon CloudFront and Amazon CloudFront Functions

This pattern deploys an Amazon Cloudfront distribution, an Amazon Cloudfront Function and a Amazon S3 Bucket and demonstrates how to implement an A/B testing solution.

Using Cloudfront Function we are changing dynamically the uri to display randomly either the old home page either the new home page.

![Pattern architecture](img/architecture.drawio.png)

The CDK application contains the minimum IAM resources required to run the application.

Learn more about this pattern at: https://serverlessland.com/patterns/cloudfront-functions-s3

Important: this application uses various AWS services and there are costs associated with these services after the Free Tier usage - please see the AWS Pricing page for details. You are responsible for any AWS costs incurred. No warranty is implied in this example.

## Requirements

* [Create an AWS account](https://portal.aws.amazon.com/gp/aws/developer/registration/index.html) if you do not already have one and log in. The IAM user that you use must have sufficient permissions to make necessary AWS service calls and manage AWS resources.
* [AWS CLI](https://docs.aws.amazon.com/cli/latest/userguide/install-cliv2.html) installed and configured
* [Git Installed](https://git-scm.com/book/en/v2/Getting-Started-Installing-Git)
* [AWS Cloud Development Kit](https://docs.aws.amazon.com/cdk/v2/guide/getting_started.html) (AWS CDK >= 2.2.0) Installed

## Language

Python

## Framework

CDK

## Services From/To

Amazon Cloudfront to Amazon Cloudfront Functions to Amazon S3

## Deployment Instructions


> **WARNING**: The resources should be deployed in N. Virginia Region (us-east-1). You must be in this region to create Lambda@Edge functions.


1. Create a new directory, navigate to that directory in a terminal and clone the GitHub repository:
    ```bash
    git clone https://github.com/aws-samples/serverless-patterns
    ```
1. Change directory to the pattern directory:
    ```bash
    cd cloudfront-cff-s3-cdk-python
    ```
1. Create a virtual environment for python:
    ```bash
    python3 -m venv .venv
    ```
1. Activate the virtual environment:
    ```bash
    source .venv/bin/activate
    ```

    If you are in Windows platform, you would activate the virtualenv like this:

    ```
    % .venv\Scripts\activate.bat
    ```

1. Install python modules:

    ```bash
    python3 -m pip install -r requirements.txt
    ```

1. From the command line, use CDK to synthesize the CloudFormation template and check for errors:

    ```bash
    cdk synth
    ```

1. From the command line, use CDK to deploy the stack:

    ```bash
    cdk deploy
    ```

    Expected result:

    ```bash
    CloudfrontCffS3CdkPythonStack

    Outputs:
    CloudfrontCffS3CdkPythonStack.DomainName = xxxxxxxxxxxx.cloudfront.net
    ```

1. Note the DomainName output from the CDK deployment process.

### Testing

1. Execute the following command several times and observe the result.

    ```bash
    curl -s -L ENTER_YOUR_DOMAIN_NAME | grep '<title>';
    ```

    Expected result:

    ```bash
    <title>B Version</title>
    <title>A Version</title>
    <title>A Version</title>
    <title>A Version</title>
    <title>A Version</title>
    <title>B Version</title>
    ```

## Cleanup

1. Delete the stack

    ```bash
    cdk destroy
    ```

## Tutorial

See [this useful workshop](https://cdkworkshop.com/30-python.html) on working with the AWS CDK for Python projects.

See [this workshop](https://catalog.us-east-1.prod.workshops.aws/v2/workshops/e507820e-bd46-421f-b417-107cd608a3b2/en-US/) on A/B testing at edge for e-commerce with 3 scenarios.

See [more Amazon Cloudfront Functions](https://github.com/aws-samples/amazon-cloudfront-functions)

## Useful commands

 * `cdk ls`          list all stacks in the app
 * `cdk synth`       emits the synthesized CloudFormation template
 * `cdk deploy`      deploy this stack to your default AWS account/region
 * `cdk diff`        compare deployed stack with current state
 * `cdk docs`        open CDK documentation

Enjoy!