Preconditions and postconditions in Terraform - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a precondition in Terraform?

A precondition is a check that runs before Terraform applies changes. It ensures certain conditions are true before continuing.

beginner

What is a postcondition in Terraform?

A postcondition is a check that runs after Terraform applies changes. It verifies that the desired state was achieved.

intermediate

How do preconditions help in Terraform deployments?

Preconditions prevent Terraform from applying changes if required conditions are not met, avoiding errors or unwanted states.

intermediate

Give an example of a Terraform precondition.

Example: Checking if a variable 'environment' is set to 'production' before applying changes to production resources.

intermediate

Why are postconditions important in Terraform?

Postconditions confirm that the infrastructure matches expectations after deployment, helping catch issues early.

What does a Terraform precondition do?

A Checks conditions before applying changes

B Checks conditions after applying changes

C Automatically fixes errors

D Deletes resources

Preconditions run before changes to ensure conditions are met.

When are postconditions evaluated in Terraform?

A Before plan phase

B After apply phase

C During initialization

D Before destroy phase

Postconditions run after apply to verify the final state.

Which Terraform block is used to define preconditions?

A check

B variable

C lifecycle

D resource

Terraform uses 'check' blocks inside resources or modules.

What happens if a precondition fails during Terraform apply?

A Terraform continues anyway

B Terraform deletes all resources

C Terraform ignores the precondition

D Terraform stops and shows an error

Terraform stops applying changes and reports the failed precondition.

Which is a benefit of using postconditions?

A They create new resources automatically

B They speed up Terraform apply

C They verify infrastructure state after changes

D They replace manual testing

Postconditions help confirm the infrastructure matches expectations.

Explain what Terraform preconditions and postconditions are and why they are useful.

Think about checks before and after making changes.

Describe a simple example of a Terraform precondition and a postcondition.

Use a variable check and a resource state check.