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Terraform

Sharing Resources Across Terraform Workspaces

By Filip on 10/07/2024

Learn how to efficiently share resources between Terraform workspaces to optimize infrastructure management and streamline your workflow.

Sharing Resources Across Terraform Workspaces

Table of Contents

Introduction

Terraform workspaces are great for managing different environments like staging and production, but they aren't meant for sharing resources directly. Each workspace has its own separate state, keeping resources isolated. If you need to share infrastructure elements between environments, there are better ways to do it.

Step-by-Step Guide

Terraform workspaces, while useful for managing different environments, aren't designed for sharing resources. Each workspace maintains its own state, isolating resources. To share infrastructure elements across environments, consider these approaches:

  1. Modularize Shared Resources: Create a separate Terraform module dedicated to provisioning and managing the shared resources. This module can be called from other modules or configurations representing different environments.

  2. Data Sources: Utilize Terraform data sources to fetch information about existing resources created by the shared module. This allows environments to access and use shared resources without managing their lifecycle.

  3. Remote State: Leverage Terraform's remote state functionality to access the state of the shared module. This enables environments to reference outputs and resources defined in the shared module's state.

  4. Avoid Sharing Resources Directly: Instead of sharing the same resource instance, consider provisioning similar resources in each environment and connecting them through appropriate means (e.g., peering VPCs, configuring cross-account access).

  5. Consider Alternatives: If extensive resource sharing is required, explore alternative tools or services designed for multi-tenancy or shared infrastructure management.

Remember, directly sharing resources between workspaces can lead to conflicts and unexpected behavior. Choose an approach that aligns with your specific needs and promotes maintainability and isolation between environments.

Code Example

The code demonstrates sharing a Google Cloud VPC network across development and production environments using Terraform. A shared module defines and creates the VPC. Both environments reference this module and use data sources to access the shared VPC information. This allows resources in each environment, like compute instances, to utilize the same VPC without directly managing its creation or deletion. This approach promotes reusability and consistency across environments.

This example demonstrates how to share a VPC network across different environments (workspaces) using a shared module and data sources.

1. Shared Module (modules/vpc):

# variables.tf
variable "vpc_cidr" {
  type = string
  default = "10.0.0.0/16"
}

# main.tf
resource "google_compute_network" "vpc" {
  name                    = "shared-vpc"
  auto_create_subnetworks = false
  project                 = "your-project-id"
}

# outputs.tf
output "vpc_id" {
  value = google_compute_network.vpc.id
}

2. Development Environment (environments/dev):

# main.tf
module "shared_vpc" {
  source = "../../modules/vpc"
}

data "google_compute_network" "shared_vpc" {
  name    = module.shared_vpc.vpc_id
  project = "your-project-id"
}

resource "google_compute_instance" "dev_instance" {
  name                      = "dev-instance"
  machine_type              = "n1-standard-1"
  boot_disk {
    initialize_params {
      image = "debian-cloud/debian-9"
    }
  }
  network_interface {
    subnetwork = "projects/your-project-id/regions/your-region/subnetworks/default" # Use the default subnetwork of the shared VPC
  }
}

3. Production Environment (environments/prod):

# main.tf
module "shared_vpc" {
  source = "../../modules/vpc"
}

data "google_compute_network" "shared_vpc" {
  name    = module.shared_vpc.vpc_id
  project = "your-project-id"
}

resource "google_compute_instance" "prod_instance" {
  name                      = "prod-instance"
  machine_type              = "n1-standard-2"
  boot_disk {
    initialize_params {
      image = "debian-cloud/debian-9"
    }
  }
  network_interface {
    subnetwork = "projects/your-project-id/regions/your-region/subnetworks/default" # Use the default subnetwork of the shared VPC
  }
}

Explanation:

  • A shared module (modules/vpc) defines and provisions the VPC network.
  • Both development and production environments include the shared module.
  • Data sources (data "google_compute_network") are used to fetch information about the shared VPC created by the shared module.
  • Resources in each environment can then utilize the shared VPC information without directly managing its lifecycle.

This example demonstrates sharing a VPC network. You can adapt this approach to share other resources like subnets, firewall rules, or even databases by creating appropriate modules and utilizing data sources or remote state.

Note: This is a simplified example. In a real-world scenario, you would likely have more complex configurations and potentially use remote state for more advanced resource sharing scenarios. Remember to carefully consider your specific needs and choose the approach that best suits your requirements.

Additional Notes

  • Security Considerations: When sharing resources like VPCs, highlight the importance of carefully managing security groups, network access control lists (ACLs), and routing to ensure proper isolation and security boundaries between environments.
  • State Management: Briefly mention that when using remote state, securely storing and accessing the state file is critical. Consider using tools like HashiCorp Vault or AWS Secrets Manager.
  • Cost Optimization: Sharing resources can lead to cost savings. However, ensure proper cost allocation and tagging strategies are in place, especially in multi-tenant environments.
  • Versioning Shared Modules: When using shared modules, emphasize the importance of versioning them properly. This ensures that changes to shared resources are rolled out in a controlled manner and environments can pin to specific versions if needed.
  • Terraform Cloud/Enterprise: For larger organizations or more complex scenarios, mention that Terraform Cloud or Terraform Enterprise offer advanced features for managing shared modules, remote state, and collaboration.
  • Real-world Examples: Provide additional examples of commonly shared resources, such as databases, security groups, or networking components, and briefly explain how the approaches mentioned earlier can be applied.
  • Community Modules: Suggest exploring the Terraform Registry for pre-built, community-maintained modules that provide shared resources. This can save time and effort compared to building everything from scratch.
  • Testing and Validation: Stress the importance of thoroughly testing any changes to shared resources in a staging environment before deploying to production to avoid unexpected issues.
  • Documentation: Highlight the need for clear documentation outlining shared resources, their configurations, and any dependencies between environments. This helps with maintainability and troubleshooting.

Summary

While Terraform workspaces are great for managing different environments, they are not designed for sharing resources directly. Here's a summary of approaches to achieve resource sharing:

Approach Description Benefits
Modularize Shared Resources Create a dedicated Terraform module for shared resources, callable from other modules/configurations. Promotes reusability and separation of concerns.
Data Sources Use data sources to fetch information about shared resources provisioned by the shared module. Allows environments to access shared resources without managing their lifecycle.
Remote State Access the state of the shared module to reference its outputs and resources. Enables referencing shared resources directly.
Avoid Direct Sharing Provision similar resources in each environment and connect them (e.g., VPC peering, cross-account access). Maintains isolation and avoids conflicts.
Consider Alternatives Explore tools designed for multi-tenancy or shared infrastructure management if extensive sharing is needed. Offers specialized solutions for complex scenarios.

Key Takeaway: Choose an approach that balances your need for resource sharing with the importance of maintainability and isolation between environments. Avoid directly sharing resources between workspaces to prevent conflicts and unexpected behavior.

Conclusion

In conclusion, while Terraform workspaces effectively manage distinct environments, they fall short in facilitating direct resource sharing. To circumvent this limitation, leverage techniques like modularizing shared resources, utilizing data sources, or employing remote state. Prioritize isolating environments and consider alternatives like multi-tenancy tools when extensive sharing is essential. Remember to prioritize security, meticulously manage state, optimize costs, and thoroughly test changes. By adhering to these principles, you can establish a robust and maintainable infrastructure with Terraform.

References

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