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Terraform

Automatically Enable GCP APIs with Terraform?

By Filip on 10/07/2024

Learn how to use Terraform to automatically enable Google Cloud Platform (GCP) APIs for seamless resource provisioning and management in your infrastructure.

Automatically Enable GCP APIs with Terraform?

Table of Contents

Introduction

When working with Terraform on Google Cloud Platform (GCP), you might need to enable specific APIs for your resources to function correctly. This article explains how to automate the process of enabling GCP APIs using Terraform, along with some considerations and potential pitfalls to keep in mind.

Step-by-Step Guide

You can automatically enable Google Cloud Platform (GCP) APIs when using Terraform by employing the google_project_service resource. This resource allows you to enable one API at a time. To enable multiple APIs, you can utilize Terraform's looping constructs like count or for_each.

For instance, you could define a variable to hold a list of APIs you want to enable:

variable "apis_to_enable" {
  type = list(string)
  default = [
    "compute.googleapis.com",
    "storage.googleapis.com",
  ]
}

Then, you can use a for_each loop to iterate over this list and enable each API:

resource "google_project_service" "enabled_api" {
  for_each = toset(var.apis_to_enable)
  service            = each.key
  disable_on_destroy = false
}

In this example, each.key within the google_project_service resource represents each API from your apis_to_enable list. The disable_on_destroy = false argument ensures that the APIs remain enabled even if you destroy the Terraform infrastructure.

However, be mindful of potential issues. Sometimes, Terraform might attempt to create resources that depend on an API before it's fully enabled. This can lead to errors. If you encounter such a situation, you might need to introduce dependencies in your Terraform code to ensure the API is enabled before other resources that rely on it are created.

Several modules and resources within the Google provider for Terraform can simplify API enabling. For example, the project-factory module offers a convenient way to enable a list of APIs during project creation. Similarly, resources like google_container_cluster might have specific options to automatically enable required APIs during their creation.

Remember that enabling APIs might have cost implications depending on the specific services and usage. Always refer to GCP pricing documentation for detailed information.

Code Example

This Terraform code defines a variable for a list of Google Cloud APIs, then iterates through the list to enable each API using the google_project_service resource. It includes an example of a google_compute_network resource that depends on the compute.googleapis.com API being enabled, demonstrating how to manage resource dependencies based on API availability.

# Define a variable to hold the list of APIs to enable
variable "apis_to_enable" {
  type = list(string)
  default = [
    "compute.googleapis.com",
    "storage.googleapis.com",
    "iam.googleapis.com",
  ]
}

# Enable each API using a for_each loop
resource "google_project_service" "enabled_api" {
  for_each = toset(var.apis_to_enable)
  service            = each.key
  disable_on_destroy = false
}

# Example resource that depends on a previously enabled API
resource "google_compute_network" "default" {
  name                    = "default"
  auto_create_subnetworks = false
  project                 = "your-project-id"

  # This resource depends on the compute.googleapis.com API being enabled
  depends_on = [google_project_service.enabled_api]
}

Explanation:

  1. Variable apis_to_enable: This variable defines a list of APIs to enable. You can customize this list with the APIs your project requires.
  2. Resource google_project_service: This resource block iterates through the apis_to_enable list using for_each and enables each API.
    • service: Specifies the API to enable (e.g., "compute.googleapis.com").
    • disable_on_destroy = false: Ensures that the APIs remain enabled even if you destroy the Terraform infrastructure.
  3. Resource google_compute_network: This is an example resource that depends on the compute.googleapis.com API.
    • depends_on: This line ensures that the google_compute_network resource is created only after the compute.googleapis.com API is enabled by the google_project_service resource.

Important Considerations:

  • Dependencies: Always consider dependencies between resources and APIs. Use the depends_on meta-argument to ensure resources are created in the correct order.
  • Cost Implications: Enabling APIs might have cost implications. Refer to GCP pricing documentation for details.
  • Alternative Approaches: Explore modules like project-factory or resource-specific options for simplified API enabling.

This example demonstrates a basic approach to automatically enabling GCP APIs with Terraform. You can adapt and expand this pattern to manage API enablement for your specific infrastructure needs.

Additional Notes

  • Best Practices:
    • Modularity: For larger projects, consider creating separate Terraform modules for enabling different groups of APIs based on their purpose (e.g., networking, storage, databases). This improves code organization and reusability.
    • Documentation: Clearly document which APIs are enabled by your Terraform code and why. This helps with understanding the project's dependencies and potential cost implications.
    • Testing: Test your Terraform code thoroughly, including scenarios where API enabling might fail. Use tools like terraform plan and terraform apply -target to test specific parts of your code.
  • Troubleshooting:
    • API Enablement Delays: If you encounter errors related to APIs not being enabled in time, try adding explicit sleep statements using time_sleep after the google_project_service resource. This can give GCP enough time to fully enable the API.
    • Permissions: Ensure that the service account used by Terraform has the necessary permissions to enable APIs in your GCP project. The roles/serviceusage.serviceUsageAdmin role is typically required.
  • Alternatives to google_project_service:
    • gcloud CLI: For simple use cases, you can use the gcloud services enable command within your Terraform configuration using the local_exec provisioner. However, this approach is less declarative and might not be ideal for complex scenarios.
    • Service Accounts: When creating resources that require specific APIs, you can often associate a service account with the resource. This service account can have the necessary permissions to enable the required APIs automatically.
  • Security Considerations:
    • Principle of Least Privilege: Only enable the APIs that are strictly necessary for your project. This reduces the potential attack surface and helps control costs.
    • API Keys: If you're using API keys for authentication, store them securely using tools like HashiCorp Vault or Google Cloud Secret Manager. Avoid hardcoding API keys directly in your Terraform code.

Summary

This article provides a concise guide on automatically enabling Google Cloud Platform (GCP) APIs using Terraform.

Key Takeaways:

  • google_project_service Resource: Enables individual GCP APIs.
  • Looping for Multiple APIs: Use Terraform's count or for_each constructs to enable multiple APIs from a list.
  • Example: 
    variable "apis_to_enable" {
  type = list(string)
  default = [
    "compute.googleapis.com",
    "storage.googleapis.com",
  ]
}

resource "google_project_service" "enabled_api" {
  for_each = toset(var.apis_to_enable)
  service            = each.key
  disable_on_destroy = false
}
  • Dependency Management: Ensure APIs are enabled before creating resources that depend on them to avoid errors.
  • Simplified Solutions: Explore modules like project-factory or resource-specific options for streamlined API enabling.
  • Cost Awareness: Be mindful of potential costs associated with enabling specific APIs and consult GCP pricing documentation.

This approach allows for efficient and automated management of GCP API activation within your Terraform infrastructure.

Conclusion

By leveraging the google_project_service resource and Terraform's looping constructs, you can efficiently enable Google Cloud APIs during your infrastructure provisioning process. Remember to manage dependencies between resources and APIs to prevent issues, and always refer to GCP's pricing documentation for potential cost implications. Utilizing modules like project-factory or resource-specific options can further streamline API enablement. By automating this process, you can ensure your Terraform deployments on GCP are smooth and error-free.

References

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