Lifecycle customization in Terraform - Step-by-Step Execution

Process Flow - Lifecycle customization

Define Resource

↓

Apply Lifecycle Block?

No→Default Create/Update/Delete

Yes↓

Check create_before_destroy

↓

Create New

↓

Check prevent_destroy

↓

Block Destroy

↓

Check ignore_changes

↓

Skip Update

↓

Resource State Updated

Terraform checks lifecycle settings to decide how to create, update, or delete resources safely.

Execution Sample

Terraform

resource "aws_instance" "example" {
  lifecycle {
    create_before_destroy = true
    prevent_destroy = true
    ignore_changes = ["tags"]
  }
}

This resource uses lifecycle rules to create new before deleting old, prevent accidental destroy, and ignore tag changes.

Process Table

Step	Lifecycle Setting Checked	Condition	Action Taken	Resource State
1	create_before_destroy	true	Create new instance before destroying old	Old and New instances exist
2	prevent_destroy	true	Block destroy operation	Destroy blocked, old instance remains
3	ignore_changes	tags changed	Ignore tag changes, no update	Instance running with old tags
4	No more lifecycle rules	-	Resource state stable	Instance running, no changes applied
5	Attempt destroy without prevent_destroy	false	Destroy allowed	Instance destroyed
6	End	-	No further actions	Final resource state stable

💡 Lifecycle rules applied to control creation, update, and destruction; execution stops when resource state is stable or destroy blocked.

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
Resource Instances	1 old instance	1 old + 1 new instance	1 old + 1 new instance (destroy blocked)	1 old + 1 new instance (tags unchanged)	1 old + 1 new instance (stable)
Destroy Allowed	false	false	false (blocked)	false	false

Key Moments - 3 Insights

Why does Terraform create a new instance before destroying the old one?

Because create_before_destroy is true (see execution_table step 1), Terraform ensures no downtime by creating the new resource first.

What happens if prevent_destroy is true and a destroy is requested?

Terraform blocks the destroy action to protect the resource (see execution_table step 2), so the old instance remains.

Why are tag changes ignored even if tags are updated in configuration?

Because ignore_changes includes tags (see execution_table step 3), Terraform skips updating tags to avoid unnecessary resource replacement.

Visual Quiz - 3 Questions

Look at the execution table, what is the resource state after step 1?

A Both old and new instances exist

B Only the old instance exists

C Only the new instance exists

D No instances exist

💡 Hint

Check the 'Resource State' column in execution_table row for step 1

At which step does Terraform block the destroy operation due to lifecycle settings?

A Step 1

B Step 2

C Step 3

D Step 5

💡 Hint

Look for 'Block destroy operation' in the 'Action Taken' column

If ignore_changes did not include tags, what would happen at step 3?

A Terraform would ignore tag changes anyway

B Terraform would destroy the instance

C Terraform would update the tags on the instance

D Terraform would block the update

💡 Hint

Refer to step 3 where ignore_changes affects tag updates

Concept Snapshot

Terraform lifecycle customization controls resource creation, update, and deletion.
Key settings:
- create_before_destroy: create new resource before deleting old
- prevent_destroy: block accidental resource deletion
- ignore_changes: skip updates to specified attributes
Use lifecycle block inside resource to apply these rules.

Full Transcript

Terraform lifecycle customization lets you control how resources are created, updated, or destroyed. When create_before_destroy is true, Terraform creates a new resource before deleting the old one to avoid downtime. If prevent_destroy is set, Terraform blocks any destroy action to protect the resource. The ignore_changes setting tells Terraform to skip updates to certain attributes, like tags, so changes there don't cause resource replacement. These lifecycle rules help manage resource state safely and predictably during infrastructure changes.