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Terraform Meta-Argument lifecycle create_before_destroy

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 create_before_destroy

Step-02: Review Terraform Manifests

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

Step-03: lifecyle - create_before_destroy

  • Default Behavior of a Resource: Destroy Resource & re-create Resource
  • With Lifecycle Block we can change that using create_before_destroy=true
  • First new resource will get created
  • Second old resource will get destroyed
  • Add Lifecycle Block inside Resource Block to alter behavior 
# Lifecycle Block inside a Resource
  lifecycle {
    create_before_destroy = true
  }

Step-04: Observe without Lifecycle Block

# Switch to Working Directory
cd terraform-manifests

# Initialize Terraform
terraform init

# Validate Terraform Configuration Files
terraform validate

# Format Terraform Configuration Files
terraform fmt

# Generate Terraform Plan
terraform plan

# Create Resources
terraform apply -auto-approve

# Modify Resource Configuration
Change Virtual Network Name from  myvnet-1 to myvnet-2

# Apply Changes
terraform apply -auto-approve
Observation: 
1) First myvnet-1 resource will be destroyed
2) Second myvnet-2 resource will get

Step-05: With Lifecycle Block

  • Add Lifecycle block in the resource (Uncomment lifecycle block)
# Generate Terraform Plan
terraform plan

# Apply Changes
terraform apply -auto-approve

# Modify Resource Configuration
Change Virtual Network Name from myvnet-2 to myvnet-1

# Apply Changes
terraform apply -auto-approve
Observation: 
1) First myvnet-1 resource will get created
2) Second myvnet-2 resource will get deleted

Step-06: Clean-Up Resources

# Destroy Resources
terraform destroy -auto-approve

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

References