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Terraform

Terraform ACM Certificate State Change After Provider Update

By Ondřej Dolanský on 12/22/2024

Troubleshooting Terraform's aws_acm_certificate state output changes after a provider update, examining potential causes and solutions.

Terraform ACM Certificate State Change After Provider Update

Table of Contents

Introduction

When working with AWS ACM certificates in Terraform, you might encounter situations where the certificate state remains in "pending validation." This can happen if DNS propagation delays cause Terraform to attempt validation before DNS records update globally, if there are incorrect DNS configurations such as missing or inaccurate CNAME records, or if Terraform provider updates introduce changes in certificate state handling. Other potential causes include issues with count and multiple certificates, data source dependencies that aren't configured to handle potential certificate unavailability, incorrect execution order or state sharing in multi-stage Terraform setups, and problems with remote state accessibility or backend configuration.

Step-by-Step Guide

When working with AWS ACM certificates in Terraform, you might encounter situations where the certificate state remains in "pending validation." This can happen if:

  1. DNS propagation delays: After updating the Name Servers for your domain, it takes time for the changes to propagate. Terraform might attempt validation before the DNS records are updated globally.

    resource "aws_acm_certificate" "example" {
  domain_name = "example.com"
  validation_method = "DNS"
}

  2. Incorrect DNS configuration: Double-check that you've created the correct CNAME records in your DNS provider's settings as instructed by AWS.

  3. Terraform provider updates: Sometimes, updates to the AWS provider might introduce changes in how certificate states are handled. Ensure you're using a compatible provider version.

    terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 3.0" 
    }
  }
}

  4. Count and multiple certificates: If you're using count to create multiple certificates, ensure the logic for generating certificate names and domains is correct.

    resource "aws_acm_certificate" "example" {
  count = length(var.domains)
  domain_name = var.domains[count.index]
}

  5. Data source dependencies: If you're using data sources that depend on the certificate, ensure they're configured to handle cases where the certificate might not be immediately available.

    data "aws_acm_certificate" "example" {
  domain = aws_acm_certificate.example.domain_name
}

  6. Multiple Terraform stages: If you're using multiple Terraform stages (e.g., separate stages for creating certificates and resources that depend on them), ensure the stages are executed in the correct order and that state is shared between them.

  7. Remote state: If you're using remote state, ensure the state file is accessible and that the correct backend configuration is used.

    terraform {
  backend "s3" {
    bucket = "my-terraform-state-bucket"
    key    = "path/to/my/state.tfstate"
    region = "us-west-2"
  }
}

If you're still facing issues, review the Terraform logs for detailed error messages and consider using tools like terraform plan and terraform apply with the -target option to debug specific resources.

Code Example

This Terraform code defines infrastructure for provisioning and using AWS ACM certificates. It sets up an AWS provider, configures optional remote state, and declares a variable for domain names. The code creates ACM certificates for each domain, fetches certificate details using a data source, and demonstrates using the certificate ARN in an example load balancer listener resource.

# main.tf

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 4.0" # Ensure a compatible version
    }
  }
}

# Configure remote state (optional)
terraform {
  backend "s3" {
    bucket = "your-terraform-state-bucket"
    key    = "path/to/your/state.tfstate"
    region = "your-aws-region"
  }
}

# Define variables for domain names
variable "domains" {
  type = list(string)
  default = ["example.com", "www.example.com"]
}

# Create ACM certificates
resource "aws_acm_certificate" "example" {
  count         = length(var.domains)
  domain_name   = var.domains[count.index]
  validation_method = "DNS"
}

# Define a data source to fetch the certificate details
data "aws_acm_certificate" "example" {
  domain = aws_acm_certificate.example[0].domain_name # Assuming you need the first certificate

  # Handle cases where the certificate might not be immediately available
  depends_on = [aws_acm_certificate.example]
}

# Example resource that depends on the certificate
resource "aws_lb_listener" "example" {
  # ... other configurations ...

  certificate_arn = data.aws_acm_certificate.example.arn
}

Explanation:

  1. Provider Version: The code specifies a compatible AWS provider version (~> 4.0).
  2. Remote State: It includes an optional terraform block for configuring remote state using S3.
  3. Variables: It defines a domains variable to store a list of domain names.
  4. Certificate Creation: The aws_acm_certificate resource creates certificates for each domain in the domains variable using the count meta-argument.
  5. Data Source: The data "aws_acm_certificate" fetches the details of the first certificate created. The depends_on meta-argument ensures that the data source is queried only after the certificate is created.
  6. Dependent Resource: An example aws_lb_listener resource demonstrates how to use the certificate ARN obtained from the data source.

Troubleshooting Tips:

  • DNS Propagation: Allow sufficient time for DNS changes to propagate after updating your domain's name servers.
  • DNS Configuration: Double-check the CNAME records created in your DNS provider's settings.
  • Terraform Logs: Review the Terraform logs (terraform apply -target=aws_acm_certificate.example) for detailed error messages.
  • State File: If using remote state, ensure the state file is accessible and the backend configuration is correct.

This comprehensive example addresses the common causes of "pending validation" states and provides guidance on troubleshooting and best practices. Remember to replace the example values with your specific configurations.

Additional Notes

  • Certificate Transparency Logging: By default, AWS ACM certificates are enrolled in Certificate Transparency logs. This might add some time to the validation process.
  • Wildcard Certificates: When requesting a wildcard certificate (e.g., *.example.com), ensure you understand the DNS validation requirements for wildcard domains.
  • Rate Limits: AWS has rate limits for ACM certificate requests. If you're creating a large number of certificates, you might encounter throttling. Consider using the AWS SDK or API to check the status of certificate requests and implement retry logic in your Terraform code.
  • Alternative Validation Methods: Besides DNS validation, AWS ACM also supports email validation. This can be useful if you don't have direct control over DNS settings.
  • Manual Validation: In some cases, you might need to manually validate a certificate through the AWS console. This is typically required for specific domain extensions or unusual DNS setups.
  • Certificate Renewal: ACM certificates are automatically renewed by default. However, it's essential to ensure that your DNS records remain valid to avoid renewal failures.
  • Import Existing Certificates: You can import existing ACM certificates into Terraform using the aws_acm_certificate data source and the import command.
  • Testing and Debugging: Use terraform plan to preview changes before applying them. The -target option can be helpful for debugging specific resources. Additionally, enable verbose logging for more detailed output.
  • Security Best Practices: Store sensitive information, such as private keys, securely using tools like AWS Secrets Manager or HashiCorp Vault. Avoid hardcoding credentials in your Terraform code.

By understanding these nuances and following best practices, you can effectively manage AWS ACM certificates with Terraform and ensure a smooth and secure deployment process.

Summary

Issue Description Solution
DNS Propagation Delays DNS changes take time to propagate globally. Terraform might attempt validation before records update. Wait for propagation or use a tool to check DNS records.
Incorrect DNS Configuration CNAME records are not correctly configured in your DNS provider. Double-check CNAME records against AWS instructions.
Terraform Provider Updates Provider updates can change how certificate states are handled. Use a compatible provider version (e.g., hashicorp/aws ~> 3.0).
Count and Multiple Certificates Logic for generating certificate names and domains using count is incorrect. Verify the logic within the count block.
Data Source Dependencies Data sources depending on the certificate are not configured to handle potential unavailability. Ensure data sources can handle cases where the certificate is not immediately available.
Multiple Terraform Stages Stages are not executed in the correct order, or state is not shared properly. Define stage dependencies and ensure state is shared between them.
Remote State State file is inaccessible, or the backend configuration is incorrect. Verify state file accessibility and correct backend configuration.

General Troubleshooting Tips:

  • Review Terraform logs for detailed error messages.
  • Use terraform plan and terraform apply with the -target option to debug specific resources.

Conclusion

To wrap up, managing AWS ACM certificates with Terraform requires careful attention to potential pitfalls like DNS propagation delays, configuration errors, and Terraform state management. By understanding these common issues and implementing the provided code examples and troubleshooting tips, you can streamline your certificate provisioning process and ensure a secure and robust infrastructure. Remember to double-check your configurations, leverage Terraform's debugging capabilities, and stay updated on AWS and Terraform best practices for optimal results.

References

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