Skip to content

Terraform Meta-Argument lifecycle ignore_changes

Step-01: Introduction

  • lifecyle Meta-Argument block contains 3 arguments
  • create_before_destroy
  • prevent_destroy
  • ignore_changes
  • We are going to practically understand and implement ignore_changes

Step-02: Review Terraform Manifests

  • c1-versions.tf
  • c2-resource-group.tf
  • c3-virtual-network.tf

Step-03: Create a Azure Virtual Network, make manual changes and understand the behavior

  • Create Azure Virtual Network
# Switch to Working Directory
cd terraform-manifests

# Initialize Terraform
terraform init

# Terraform Validate
terraform validate

# Terraform Plan 
terraform plan

# Terraform Apply 
terraform apply

Step-04: Update the tag by going to Azure management console

  • Add a new tag manually to Azure Virtual Network Resource
  • Try terraform apply now
  • Terraform will find the difference in configuration on remote side when compare to local and tries to remove the manual change when we execute terraform apply
# Add new tag manually using Azure Portal
WebServer = Apache

# Terraform Plan 
terraform plan

# Terraform Apply 
terraform apply 
Observation: 
1) It will remove the changes which we manually added using Azure Management console

Step-05: Add the lifecyle - ignore_changes block

  • Enable the block in c3-virtual-network.tf
# Lifecycle Block
   lifecycle {
    ignore_changes = [
      # Ignore changes to tags, e.g. because a management agent
      # updates these based on some ruleset managed elsewhere.
      tags,
    ]
  }
  • Add new tags manually using Azure Management console for Azure Virtual Network Resource
# Add new tag manually
WebServer = Apache2
ignorechanges = test1

# Terraform Plan 
terraform plan

# Terraform Apply 
terraform apply 
Observation: 
1) Manual changes should not be touched. They should be ignored by terraform
2) Verify the same on Azure management console

Step-06: Lets see the downside of this Lifecycle Block

  • Add new tag from Terraform Configs by editing the c3-virtual-network.tf
# Terraform Plan
terraform plan
Observation:
1. "No changes" will be reported as we cannot add new tag because it is present in ignore_changes lifecycle block

# Terraform Apply
terraform apply
Observation:
1. "No changes" will be reported as we cannot add new tag because it is present in ignore_changes lifecycle block

Step-07: Clean-Up

# Destroy Resource
terraform destroy -auto-approve

# Clean-Up
rm -rf .terraform*
rm -rf terraform.tfstate*

References