AWS Region-Specific Information Directory

Usage

Some information used in CDK Applications differs from one AWS region to another, such as service principals used in IAM policies, S3 static website endpoints, ...

The RegionInfo class

The library offers a simple interface to obtain region specific information in the form of the RegionInfo class. This is the preferred way to interact with the regional information database:

// Get the information for "eu-west-1":
const region = regionInfo.RegionInfo.get('eu-west-1');

// Access attributes:
region.s3StaticWebsiteEndpoint; // s3-website-eu-west-1.amazonaws.com
region.servicePrincipal('logs.amazonaws.com'); // logs.eu-west-1.amazonaws.com

The RegionInfo layer is built on top of the Low-Level API, which is described below and can be used to register additional data, including user-defined facts that are not available through the RegionInfo interface.

Low-Level API

This library offers a primitive database of such information so that CDK constructs can easily access regional information. The FactName class provides a list of known fact names, which can then be used with the RegionInfo to retrieve a particular value:

const codeDeployPrincipal = regionInfo.Fact.find('us-east-1', regionInfo.FactName.servicePrincipal('codedeploy.amazonaws.com'));
// => codedeploy.us-east-1.amazonaws.com

const staticWebsite = regionInfo.Fact.find('ap-northeast-1', regionInfo.FactName.S3_STATIC_WEBSITE_ENDPOINT);
// => s3-website-ap-northeast-1.amazonaws.com

Supplying new or missing information

As new regions are released, it might happen that a particular fact you need is missing from the library. In such cases, the Fact.register method can be used to inject FactName into the database:

class MyFact implements regionInfo.IFact {
  public readonly region = 'bermuda-triangle-1';
  public readonly name = regionInfo.FactName.servicePrincipal('s3.amazonaws.com');
  public readonly value = 's3-website.bermuda-triangle-1.nowhere.com';
}

regionInfo.Fact.register(new MyFact());

Overriding incorrect information

In the event information provided by the library is incorrect, it can be overridden using the same Fact.register method demonstrated above, simply adding an extra boolean argument:

class MyFact implements regionInfo.IFact {
  public readonly region = 'us-east-1';
  public readonly name = regionInfo.FactName.servicePrincipal('service.amazonaws.com');
  public readonly value = 'the-correct-principal.amazonaws.com';
}

regionInfo.Fact.register(new MyFact(), true /* Allow overriding information */);

If you happen to have stumbled upon incorrect data built into this library, it is always a good idea to report your findings in a GitHub issue, so we can fix it for everyone else!

This module is part of the AWS Cloud Development Kit project.