AWS AppConfig

Core Concepts of AWS AppConfig

To effectively use AWS AppConfig, you need to understand its fundamental components. These components work together to provide a controlled and reliable configuration management system.

1. Application

An "Application" in AWS AppConfig is a logical grouping for your configuration settings. It acts as a container and is typically named after the application you are configuring. For example, MyWebApp or MobileAppBackend.

2. Environment

Environments represent the deployment targets for your configuration, such as development, testing, and production. Each environment is a logical deployment group and can have its own specific configuration values and deployment settings. This allows you to test changes in a development environment before promoting them to production.

3. Configuration Profile

A Configuration Profile defines the source and structure of your configuration data. It links your AppConfig environment to the actual configuration data. AppConfig supports two types of profiles:

• Freeform Configuration Profiles: These can store any type of data, such as text, JSON, YAML, or binary data.

• Feature Flag Profiles: These are structured specifically for managing feature flags, allowing you to turn features on or off at runtime.

You can source your configuration data from:

• AWS AppConfig hosted configuration store

• AWS Systems Manager (SSM) Document

• AWS Systems Manager (SSM) Parameter Store

• Amazon S3

4. Deployment Strategy

A Deployment Strategy controls how your configuration changes are rolled out to your application instances. This is a critical feature for minimizing risk. AppConfig provides pre-defined strategies and allows you to create custom ones.

• Pre-defined Strategies:

  • AppConfig.AllAtOnce: Deploys the change to all targets immediately. This is fast but risky.

  • AppConfig.Linear50PercentEvery30Seconds: Rolls out to 50% of targets, waits 30 seconds, then deploys to the remaining 50%.

  • AppConfig.Canary10Percent20Minutes: Deploys to 10% of targets, bakes for 20 minutes, then deploys to the rest.

• Custom Strategies: You can define your own rollout pace, specifying the growth factor (linear or exponential) and the time between steps.

How AWS AppConfig Works

The process involves creating the configuration, deploying it, and then fetching it from your application.

1. Create Configuration: You define your configuration data in one of the supported sources (e.g., AppConfig's hosted store or SSM Parameter Store).

2. Create a Deployment: You start a deployment through the AWS Console or API, selecting the Application, Environment, Configuration Profile, a specific configuration version, and a Deployment Strategy.

3. Controlled Rollout: AppConfig uses the specified deployment strategy to gradually release the new configuration. It monitors for alarms you've configured (via Amazon CloudWatch) during the rollout.

4. Automatic Rollback: If a CloudWatch alarm is triggered during the deployment, AppConfig automatically rolls back the change to the previous stable configuration. This prevents a faulty configuration from affecting all your users.

5. Fetch Configuration: Your application code makes API calls to AWS AppConfig to retrieve the latest deployed configuration. The AppConfig Agent can be used to streamline this process by caching configurations locally, reducing latency and API costs.

Key Features and Benefits

• Safe and Controlled Deployments: Minimize risk by using gradual deployment strategies and automatic rollbacks based on CloudWatch alarms.

• Configuration Validation: You can create validators (either a JSON Schema or an AWS Lambda function) to check your configuration data for correctness before it can be deployed. This prevents syntactical or semantic errors from ever reaching your application.

• Decoupling Configuration from Code: Update application behavior without deploying new code. This is ideal for managing feature flags, A/B testing, and operational tuning.

• Centralized Management: Manage configurations for applications running on EC2 instances, AWS Lambda, containers (ECS/EKS), mobile apps, and IoT devices from a single place.

• Integration with AWS Services: Natively integrates with other AWS services like SSM, S3, and CloudWatch for a seamless workflow.

Use Cases for AWS AppConfig

• Feature Flags: Enable or disable features in real-time without a code push.

• Allow/Block Lists: Update lists of users or tenants who can access certain features.

• Throttling & Operational Tuning: Adjust application behavior, such as log levels or throttling limits, in response to production events.

• A/B Testing: Deploy different configurations to different segments of users to test new features.