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Terraform Ephemeral Resources

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  • User AvatarPradip
  • 11 Nov, 2025
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  • 3 Mins Read

Terraform Ephemeral Resources

Terraform Ephemeral Resources in Azure: A Complete Guide

If you’re managing Azure infrastructure with Terraform, you’ve likely encountered this challenge: how do you effectively handle ephemeral resources—those temporary environments for testing, development, and pipelines that need to be created and destroyed efficiently?

Managing these Azure ephemeral environments with the same processes as your production infrastructure can be cumbersome and risky. In this comprehensive guide, you’ll learn Azure-specific patterns and tools to manage Terraform ephemeral resources effectively, ensuring clean creation and destruction without impacting your core Azure infrastructure.

What Are Ephemeral Resources in Azure?

Ephemeral resources are temporary Azure services created for a short duration and automatically destroyed or replaced as part of a workflow.

Typical examples in Azure include:

  • Ephemeral Compute Instances created via Azure Virtual Machine Scale Sets (VMSS)

  • Temporary environments used in Dev/Test/Sandbox

  • Short-lived Kubernetes node pools in AKS

  • Ephemeral disks for high-performance workloads

  • Temporary Azure Functions or Logic App executions

  • Ephemeral managed identities or tokens

  • Ephemeral storage on Azure Spot VMs

These resources often come and go dynamically, outside the predictable lifecycle of traditional infrastructure.

How Terraform Handles Ephemeral Resources in Azure

Terraform provides several mechanisms to effectively manage Azure’s dynamic, short-lived resource behavior.

Use ignore_changes for Azure Auto-managed attributes

Many Azure resources modify attributes automatically—for example, VMSS instance counts, IP addresses, tags, and OS version upgrades.

Terraform can ignore those drift-causing attributes.

Example:

resource "azurerm_virtual_machine_scale_set" "vmss" {
name = "test-vmss"
resource_group_name = azurerm_resource_group.rg.name
location = azurerm_resource_group.rg.location

sku {
capacity = 2
name = "Standard_DS1_v2"
}

lifecycle {
ignore_changes = [
sku[0].capacity
]
}
}

This prevents Terraform from fighting Azure’s autoscaling engine.

Use create_before_destroy for safe replacement

Azure frequently replaces disks, NICs, or scale set nodes.

Terraform prevents downtime by creating replacements first:

lifecycle {
create_before_destroy = true
}

Azure Ephemeral OS Disk Support

Azure provides Ephemeral OS Disks for fast, temporary compute.

Terraform supports this:

resource "azurerm_linux_virtual_machine" "example" {
name = "ephemeral-vm"

ephemeral_os_disk {
disk_size_gb = 64
}
}

These VMs are perfect for CI/CD, batch jobs, and disposable workloads.

Using null_resource for temporary tasks

Terraform can perform temporary provisioning actions without creating persistent resources.

resource "null_resource" "ephemeral_task" {
triggers = {
run_id = timestamp()
}

provisioner "local-exec" {
command = "az login"
}
}

This is used for:

  • Running scripts

  • Temporary task execution

  • Automation hooks

No state problems, as they don’t represent actual Azure resources.

Ephemeral Environments With Terraform Workspaces

Azure DevOps/GitHub Actions pipelines often create:

  • Ephemeral DEV environments per branch

  • Ephemeral PR environments

  • Ephemeral QA/UAT test infra

Using workspaces:

terraform workspace new feature123
terraform apply -auto-approve
# run tests
terraform destroy -auto-approve
terraform workspace delete feature123

Clean, isolated, zero-clutter environments.

Ephemeral AKS Node Pools

AKS autoscaling is common.

Terraform config:

resource "azurerm_kubernetes_cluster_node_pool" "app_pool" {
name = "app"
enable_auto_scaling = true
min_count = 1
max_count = 5

lifecycle {
ignore_changes = [
node_count
]
}
}

Automatic scale actions won’t conflict with Terraform.

Best Practices for Ephemeral Resources in Azure

  • Use ignore_changes for autoscale and dynamic attributes
  • Use ephemeral OS disks for fast, temporary compute workloads
  • Use Spot VMs for cheap, disposable compute
  • Maintain separate workspaces for ephemeral environments
  • Always run terraform refresh before manual debugging
  • Avoid tracking VMSS instances individually
  • Use Terraform Cloud/DevOps pipeline for environment lifecycle

Real-World Use Cases

Scenario 1: Temporary Performance Testing Environment

  • Deploy ephemeral VM clusters

  • Run load testing

  • Destroy environment

Scenario 2: AKS Autoscaling Node Pools

  • AKS expands/shrinks automatically

  • Terraform only manages base configuration

Scenario 3: CI/CD pipeline ephemeral infrastructure

  • Create infra

  • Run tests

  • Destroy infra

Scenario 4: Ephemeral OS disks for ML workloads

  • High IOPS

  • Zero cost for persistent storage

  • Automatic wipe on VM stop

Conclusion

Terraform remains a powerful tool for Azure IaC, and with the right patterns, you can manage ephemeral resources effectively. Azure’s dynamic nature—VMSS, AKS, Spot VMs, ephemeral OS disks—requires careful lifecycle management, but Terraform’s built-in mechanisms like ignore_changes, workspaces, and lifecycle rules make it extremely capable.

Ephemeral resources can dramatically reduce cost, accelerate testing, and enhance DevOps automation—especially on Azure.

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