For_each for map-based instances in Terraform - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does for_each do in Terraform when used with a map?

for_each lets you create multiple resources, one for each item in the map. Each resource gets a unique key from the map.

beginner

How do you access the key and value inside a for_each block for a map?

Use each.key for the map key and each.value for the map value inside the resource block.

intermediate

Why is using a map with for_each better than a list for some cases?

<p>Maps let you name each instance with a key, making it easier to identify and update specific resources.</p>

intermediate

What happens if you change the keys in the map used by for_each?

Terraform will see the old keys as removed and new keys as added, so it will destroy and create resources accordingly.

beginner

Show a simple example of for_each with a map to create multiple AWS EC2 instances.

resource "aws_instance" "example" {
  for_each = {
    web1 = "t2.micro"
    web2 = "t2.small"
  }

  ami           = "ami-123456"
  instance_type = each.value
  tags = {
    Name = each.key
  }
}

What does each.key represent in a for_each loop over a map?

A The index number of the item

B The key of the current map item

C The value of the current map item

D The total number of items

each.key is the key from the map for the current resource instance.

If you want to create resources with names from a map, which Terraform feature helps you do this easily?

A for_each

B count

C variable interpolation

D locals

for_each lets you create one resource per map entry, using keys as names.

What happens if you use a list instead of a map with for_each?

A Terraform will fail to apply

B Terraform will create only one resource

C Terraform will use list indexes as keys

D Terraform will ignore the list

Terraform uses list indexes as keys when for_each is given a list.

Why should you avoid changing keys in a map used by for_each after deployment?

A It automatically updates resources without changes

B It improves performance

C It makes Terraform ignore the resources

D It causes Terraform to recreate resources

Changing keys makes Terraform think old resources are removed and new ones added, causing recreation.

In the example for_each = { web1 = "t2.micro", web2 = "t2.small" }, what is each.value for the resource named web2?

A "t2.small"

B null

C "t2.micro"

D "web2"

each.value is the value from the map for the current key, so for web2 it is "t2.small".

Explain how for_each works with maps in Terraform and why it is useful.

Think about how maps have keys and values and how Terraform uses them.

Describe what happens if you rename a key in the map used by for_each after resources are created.

Consider how Terraform tracks resources by keys.