Terraform Import Certs Fails: EDGE vs REGIONAL Issue

• Introduction
• Step-by-Step Guide
• Code Example
• Additional Notes
• Summary
• Conclusion
• References

When using custom domain names with AWS API Gateway, you'll encounter two types: Edge-optimized and Regional. Understanding their differences is key to a successful API deployment. This guide clarifies the distinctions between these endpoint types and addresses a common challenge: importing certificates for Regional custom domain names using Terraform. We'll explore why this issue occurs and provide a step-by-step solution to use your own certificates with Regional API Gateways.

When working with API Gateway custom domain names in AWS, it's crucial to understand the distinction between Edge-optimized and Regional endpoints. Edge-optimized endpoints are best for globally distributed clients, routing traffic through CloudFront. Regional endpoints are suitable for clients within a specific AWS region, offering lower latency within that region.

A common issue arises when attempting to import certificates for a Regional custom domain name using Terraform. This is because Regional domain names don't directly use certificates. Instead, they rely on an AWS-managed certificate for the *.execute-api.{region}.amazonaws.com domain.

If you need to use your own certificate with a Regional API Gateway, you must create an Edge-optimized custom domain name. This domain name can then be associated with your Regional API Gateway.

Here's a breakdown:

1. Regional API Gateway Custom Domain Names:

   • Use an AWS-managed certificate.
   • Don't directly support importing your own certificates.
   • Suitable for clients within the same AWS region.

2. Edge-optimized API Gateway Custom Domain Names:

   • Allow importing your own certificates.
   • Use CloudFront for global traffic distribution.
   • Can be associated with Regional API Gateways.

To resolve the issue of importing certificates for a Regional API Gateway:

1. Create an Edge-optimized custom domain name in API Gateway.
2. Import your certificate into ACM (AWS Certificate Manager).
3. Associate the Edge-optimized domain name with your Regional API Gateway.

This setup allows you to leverage your certificate while still benefiting from the regional endpoint for your API Gateway.

This Terraform code sets up a Regional API Gateway with a custom domain name and SSL certificate. It creates an ACM certificate, an Edge-optimized API Gateway domain name linked to the certificate, a Regional API Gateway, and a base path mapping to connect the domain to the API Gateway. This allows traffic to be routed through CloudFront with your custom domain and SSL certificate.

# Configure the AWS Provider
terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 4.0"
    }
  }
}

# Configure the AWS Region
provider "aws" {
  region = "us-east-1" # Replace with your desired region
}

# Create an ACM certificate
resource "aws_acm_certificate" "example" {
  domain_name       = "api.example.com" # Replace with your domain name
  validation_method = "DNS"

  # Configure DNS validation records
  # ...
}

# Create an Edge-optimized API Gateway custom domain name
resource "aws_api_gateway_domain_name" "example" {
  domain_name = "api.example.com" # Replace with your domain name

  certificate_arn = aws_acm_certificate.example.arn

  endpoint_configuration {
    types = ["EDGE"]
  }
}

# Create a Regional API Gateway
resource "aws_api_gateway_rest_api" "example" {
  name        = "example"
  description = "Example API Gateway"
}

# Create a base path mapping to associate the Edge-optimized domain name with the Regional API Gateway
resource "aws_api_gateway_base_path_mapping" "example" {
  api_id      = aws_api_gateway_rest_api.example.id
  domain_name = aws_api_gateway_domain_name.example.domain_name

  stage_name = "prod" # Replace with your stage name
}

Explanation:

1. Certificate Creation: The code creates an ACM certificate for your custom domain name (api.example.com in this example). You'll need to configure DNS validation records separately.
2. Edge-optimized Domain Name: An Edge-optimized API Gateway custom domain name is created, associating it with the ACM certificate.
3. Regional API Gateway: A standard Regional API Gateway is created.
4. Base Path Mapping: A base path mapping connects the Edge-optimized domain name to the Regional API Gateway. This allows traffic to be routed through CloudFront (using your custom certificate) and then to the Regional API Gateway endpoint.

Note: This code snippet provides a basic example. You'll need to adapt it based on your specific requirements, such as adding API resources, methods, and integrations.

• Cost implications: Edge-optimized endpoints may incur slightly higher costs due to CloudFront usage. Consider this when choosing between Regional and Edge-optimized.
• Certificate management: While Regional endpoints use AWS-managed certificates, you're responsible for managing certificates for Edge-optimized endpoints (renewal, etc.).
• DNS configuration: For both endpoint types, you'll need to configure DNS records to point your custom domain to the API Gateway endpoint.
• Alternative solutions: If you absolutely need to use your own certificate with a Regional endpoint and cannot use an Edge-optimized endpoint, consider using an Application Load Balancer (ALB) in front of your API Gateway. This allows for more flexible certificate management but adds complexity.
• Security: Both endpoint types can be secured using API keys, IAM authorization, or Lambda authorizers.
• Troubleshooting: When encountering issues, API Gateway logs and CloudFront logs (for Edge-optimized) are invaluable for debugging.
• Terraform best practices: Use modules to organize your Terraform code and make it reusable. Consider using variables for values like domain names and regions to make your code more flexible.
• Keep updated: AWS services evolve constantly. Stay informed about new features and best practices related to API Gateway and custom domain names.

Problem: You cannot import custom certificates for Regional API Gateway custom domain names.

Solution:

1. Create an Edge-optimized custom domain name in API Gateway.
2. Import your certificate into AWS Certificate Manager (ACM).
3. Associate the Edge-optimized domain name with your Regional API Gateway.

This allows you to use your own certificate while still benefiting from the lower latency of a Regional API Gateway endpoint for clients within the same region.

In conclusion, understanding the differences between Edge-optimized and Regional custom domain names in AWS API Gateway is essential for efficient and secure API deployments. While Regional endpoints offer lower latency within a specific AWS region, they rely on AWS-managed certificates and don't directly support importing your own. Edge-optimized endpoints, on the other hand, leverage CloudFront for global traffic distribution and allow you to use your own certificates. To overcome the challenge of importing certificates for Regional API Gateways, create an Edge-optimized custom domain name, import your certificate, and associate it with your Regional API Gateway. This setup combines the benefits of both endpoint types, providing secure and efficient communication for your globally distributed applications. Remember to consider factors like cost implications, certificate management, DNS configuration, and security best practices when choosing the right approach for your specific needs. By staying informed about AWS updates and leveraging tools like Terraform, you can streamline your API Gateway deployments and ensure optimal performance and security for your applications.

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