How Do I Interpolate AWS Account ID Into an ARN String?

Introduction

Interpolating your AWS account ID into an Amazon Resource Name (ARN) string is essential for dynamically referencing AWS resources within your infrastructure code. This process ensures that your code can adapt to different AWS accounts without manual changes, enhancing both flexibility and scalability.

Step-by-Step Explanation

The generated ARN string usually follows the format: arn:aws:<service>:<region>:<account-id>:<resource>. In this tutorial, we will use TypeScript and the Pulumi library to interpolate the AWS account ID into an ARN string.

Here’s a complete example that defines the necessary configuration, retrieves the AWS caller identity, and interpolates the AWS account ID to create an ARN string.

import * as pulumi from "@pulumi/pulumi";
import * as aws from "@pulumi/aws";

// Retrieve the AWS account ID
const current = aws.getCallerIdentityOutput({});
export const myArn = current.apply(current => `arn:aws:iam::${current.accountId}:role/my-role`);
export const interpolatedArn = current.apply(current => current.accountId);

Breakdown of the Code

1. Import Modules: We import the necessary modules from Pulumi and AWS SDK to interact with AWS resources.
2. Retrieve AWS Account ID: The aws.getCallerIdentityOutput({}) function is used to obtain the AWS account ID of the current caller identity.
3. Interpolate ARN: Using the apply method, we interpolate the AWS account ID into the ARN string for an IAM role. The string takes the form arn:aws:iam::<account-id>:role/my-role.
4. Set Outputs: The interpolated ARN string is exported as an output, allowing you to use it in other parts of your infrastructure code.

Key Points

• Interpolating AWS account IDs into ARNs is crucial for creating adaptable and reusable infrastructure code.
• The process involves retrieving the account ID and dynamically inserting it into the ARN string.
• Pulumi’s apply method is used to handle the interpolation in a seamless manner.

Conclusion

Incorporating AWS account ID interpolation into your infrastructure setup allows for more dynamic and portable code. This approach is particularly beneficial in scenarios where the same code needs to be deployed across multiple AWS accounts. By understanding and applying these concepts, you can enhance the scalability and flexibility of your AWS infrastructure management.