Resource dependencies (implicit) in Terraform - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are implicit resource dependencies in Terraform?

Implicit resource dependencies happen automatically when one resource uses an attribute from another resource. Terraform understands the order to create resources without extra instructions.

beginner

How does Terraform detect implicit dependencies?

Terraform detects implicit dependencies by looking at references in resource arguments. If a resource uses another resource's output, Terraform knows to create the second resource after the first.

intermediate

Why are implicit dependencies preferred over explicit dependencies in Terraform?

Implicit dependencies keep configurations simple and clean. Terraform automatically manages the order, reducing errors and extra code compared to manually specifying dependencies.

beginner

Give an example of an implicit dependency in Terraform.

If a virtual machine resource uses the ID of a network resource, Terraform knows to create the network first. For example, vm.network_id = network.id creates an implicit dependency.

intermediate

Can implicit dependencies handle all resource creation order needs?

Most of the time, yes. But sometimes explicit dependencies are needed when resources don’t directly reference each other but still require order.

What triggers an implicit dependency in Terraform?

A Running terraform plan

B One resource referencing another resource's attribute

C Using depends_on explicitly

D Using variables only

Implicit dependencies happen when a resource uses another resource's attribute, so Terraform knows the order automatically.

Which is true about implicit dependencies?

A Terraform detects them automatically

B They require manual declaration

C They slow down resource creation

D They are not recommended

Terraform automatically detects implicit dependencies by analyzing resource references.

When might you need to use explicit dependencies instead of implicit?

A When resources do not reference each other but need order

B When using variables

C When creating only one resource

D When using modules

Explicit dependencies are needed when resources don’t reference each other but must be created in a specific order.

What happens if Terraform does not detect a needed dependency?

A Terraform creates resources in random order

B Terraform fails to plan

C Terraform creates resources in parallel, possibly causing errors

D Terraform ignores the resource

Without proper dependencies, Terraform may create resources in parallel, which can cause errors if order matters.

Which Terraform argument is used for explicit dependencies?

A require

B reference

C depends

D depends_on

The depends_on argument is used to explicitly declare resource dependencies.

Explain how Terraform uses implicit dependencies to manage resource creation order.

Think about how one resource's input can come from another resource's output.

Describe a situation where implicit dependencies are not enough and explicit dependencies are needed.

Consider resources that must be created in sequence but don’t share attributes.