AWS AppConfig Feature Flag with SAM

This pattern creates

• AWS AppConfig Feature Flag configuration
• AWS Lambda that reads the feature flags from AWS AppConfig
• Amazon API Gateway HTTP API that triggers the AWS Lambda

The feature flag configuration in this example contains two flags:

• a simple boolean flag ON/OFF
• a flag that can be ON/OFF but, when it is ON, it has a numeric value

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 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 installed and configured
• Git Installed
• AWS Serverless Application Model (AWS SAM) installed

Deployment Instructions

1. Create a new directory, navigate to that directory in a terminal and clone the GitHub repository:

   git clone https://github.com/aws-samples/serverless-patterns
   

2. Change directory to the pattern directory:

   cd appconfig-feature-flag-sam
   

3. From the command line, use AWS SAM to build and deploy the AWS resources for the pattern as specified in the template.yml file:

   sam build
   sam deploy --guided
   

4. During the prompts:

   • Enter a stack name: eg. appconfig-feature-flag-sam
   • Enter the desired AWS Region: eg. us-east-1
   • Enter the Application Name to identify the application in AWS AppConfig: appconfig-feature-flag-sam
   • Enter the Environment Name: eg. dev
   • Enter the name of the Feature Flag configuration: TestConfig
   • Enter the AWS AppConfig Lambda extension arn for your Region from https://docs.aws.amazon.com/appconfig/latest/userguide/appconfig-integration-lambda-extensions-versions.html#appconfig-integration-lambda-extensions-enabling-x86-64
   • Allow SAM CLI to create IAM roles with the required permissions.

   Once you have run sam deploy -guided mode once and saved arguments to a configuration file (samconfig.toml), you can use sam deploy in future to use these defaults.

5. Note the outputs from the SAM deployment process. These contain the resource names and/or ARNs which are used for testing.

How it works

This pattern deploys an Amazon API Gateway HTTP API that, throuogh the config endpoint, triggers the AWS Lambda. The function retrieves the feature flags fron AWS AppConfig.

The AWS Lambda is configured to have access to the application's configuration for a specific environment.

Testing

Once the application is deployed, retrieve the HttpApiUrl value from CloudFormation Outputs. Either browse to the endpoint in a web browser or call the endpoint from Postman. Remeber to append the path of the endpoint that retrieves the configuration (config)

Example GET Request: https://{HttpApiId}.execute-api.eu-west-1.amazonaws.com/config

Response:

{
  "Pagination":{
    "Enabled":true,"PageSize":5
    },
  "WizardSwitch":{
    "Enabled":true
    }
}

Documentation

• AWS AppConfig
• AWS AppConfig Feature Flag
• AWS AppConfig integration with Lambda extensions
• Learn to Use AWS AppConfig Feature Flags

Cleanup

1. Delete the stack

   sam delete 

This pattern was contributed by Greg Davis.

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SPDX-License-Identifier: MIT-0