For_each for map-based instances in Terraform - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to use a map with for_each to create instances.

Terraform

resource "aws_instance" "example" {
  for_each = [1]
  ami           = each.value.ami
  instance_type = each.value.instance_type
}

Drag options to blanks, or click blank then click option'

Avar.instances

Bvar.instance_list

Caws_instance.example

Dlocal.instances

Attempts:

3 left

💡 Hint

Common Mistakes

Using a list variable instead of a map for for_each.

Referencing a resource instead of a variable.

The for_each argument expects a map or set of strings. Here, var.instances is the map variable holding instance details.

2fill in blank

medium

Complete the code to access the instance type from the map value.

Terraform

instance_type = [1].instance_type

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Avar.instances

Blocal.instance

Ceach.value

Deach.key

Attempts:

3 left

💡 Hint

Common Mistakes

Using each.key which is the map key, not the value.

Using variable names instead of each.

Within a for_each block, each.value accesses the current map value, which contains the instance details.

3fill in blank

hard

Fix the error in the for_each expression to correctly iterate over the map variable.

Terraform

for_each = [1]

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Avar.instances

Bvar.instances[*]

Cvar.instances[]

Dvar.instances.all

Attempts:

3 left

💡 Hint

Common Mistakes

Using list or index syntax on a map variable.

Trying to access a non-existent property like .all.

The for_each expects a map or set of strings. Using var.instances directly is correct. Using var.instances[*] tries to convert to a list, which is invalid here.

4fill in blank

hard

Fill both blanks to create a map of instance names to AMI IDs using for_each.

Terraform

output "instance_amis" {
  value = { for name, details in [1] : name => details.[2] }
}

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Avar.instances

Bvar.instance_list

Cami

Dinstance_type

Attempts:

3 left

💡 Hint

Common Mistakes

Using a list variable instead of a map for iteration.

Accessing the wrong property like instance_type instead of ami.

The for expression iterates over var.instances map. The value accessed is the AMI ID, so details.ami is correct.

5fill in blank

hard

Fill all three blanks to define multiple AWS instances using for_each with map variable and set tags.

Terraform

resource "aws_instance" "web" {
  for_each = [1]
  ami           = each.value.[2]
  instance_type = each.value.instance_type
  tags = {
    Name = [3]
  }
}

Drag options to blanks, or click blank then click option'

Avar.instances

Bami

Ceach.key

Dlocal.instances

Attempts:

3 left

💡 Hint

Common Mistakes

Using a list variable instead of a map for for_each.

Accessing the wrong property for AMI.

Using a fixed string instead of each.key for the Name tag.

for_each uses the map variable var.instances. The AMI is accessed by each.value.ami. The tag Name uses the map key each.key to name each instance uniquely.

Practice

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

easy

A. Creates resources only for the first key in the map

B. Deletes all resources in the map

C. Combines all map entries into a single resource

D. Creates one resource for each key-value pair in the map

Solution

1. Step 1: Understand the role of for_each with maps

   for_each iterates over each key-value pair in a map to create multiple resources.

2. Step 2: Recognize resource creation behavior

   Each key-value pair results in one resource instance, using each.key and each.value inside the resource block.

3. Final Answer:

   Creates one resource for each key-value pair in the map -> Option D

4. Quick Check:

   for_each with map = one resource per pair [OK]

Hint: Remember: for_each maps keys to separate resources [OK]

Common Mistakes:

• Thinking for_each merges all map entries into one resource
• Assuming for_each deletes resources
• Believing for_each only uses the first map key

2. Which of the following is the correct syntax to use for_each with a map in a Terraform resource?

easy

A. resource "aws_instance" "example" { for_each = { key1 = "val1", key2 = "val2" } }

B. resource "aws_instance" "example" { for_each = ("key1", "key2") }

C. resource "aws_instance" "example" { for_each = "key1" }

D. resource "aws_instance" "example" { for_each = ["one", "two"] }

Solution

1. Step 1: Identify valid for_each types

   for_each accepts a map or set of strings, but here we focus on map usage.

2. Step 2: Check syntax correctness

   resource "aws_instance" "example" { for_each = { key1 = "val1", key2 = "val2" } } uses a map with key-value pairs correctly inside curly braces, which is valid Terraform syntax.

3. Final Answer:

   resource "aws_instance" "example" { for_each = { key1 = "val1", key2 = "val2" } } -> Option A

4. Quick Check:

   Map syntax with curly braces = correct for_each [OK]

Hint: Use curly braces for maps in for_each [OK]

Common Mistakes:

• Using square brackets for maps instead of curly braces
• Passing a single string instead of a map
• Using parentheses which are invalid here

3. Given the Terraform snippet:

variable "servers" {
  default = {
    web = "10.0.0.1"
    db  = "10.0.0.2"
  }
}

resource "aws_instance" "example" {
  for_each = var.servers
  ami           = "ami-123456"
  instance_type = "t2.micro"
  tags = {
    Name = each.key
    IP   = each.value
  }
}

What will be the value of the tag Name for the instance with IP 10.0.0.2?

medium

A. web

B. 10.0.0.2

C. db

D. example

Solution

1. Step 1: Map keys to IP addresses

   The map has keys 'web' and 'db' with values '10.0.0.1' and '10.0.0.2' respectively.

2. Step 2: Match IP to key

   The IP '10.0.0.2' corresponds to the key 'db', so the tag Name will be 'db'.

3. Final Answer:

   db -> Option C

4. Quick Check:

   each.key for IP 10.0.0.2 = db [OK]

Hint: Match IP value to map key for Name tag [OK]

Common Mistakes:

• Confusing key and value in the map
• Using IP as the Name tag instead of the key
• Assuming static tag values

4. What is wrong with this Terraform resource using for_each on a map?

resource "aws_instance" "example" {
  for_each = { "one" = "10.0.0.1", "two" = "10.0.0.2" }
  ami           = "ami-123456"
  instance_type = "t2.micro"
  tags = {
    Name = each.value
  }
  count = 2
}

medium

A. Using both for_each and count together causes an error

B. The map syntax is invalid

C. Missing each.key in tags

D. AMI ID is incorrect

Solution

1. Step 1: Check resource meta-arguments

   Terraform does not allow using both for_each and count in the same resource block.

2. Step 2: Identify the error cause

   The presence of count = 2 alongside for_each causes a configuration error.

3. Final Answer:

   Using both for_each and count together causes an error -> Option A

4. Quick Check:

   for_each and count cannot coexist [OK]

Hint: Never mix for_each and count in one resource [OK]

Common Mistakes:

• Thinking map syntax is wrong
• Believing missing each.key causes error
• Assuming AMI ID is the problem

5. You have a map of server roles and IPs:

servers = {
  app1 = "10.0.1.1"
  app2 = ""
  app3 = "10.0.1.3"
  app4 = null
}

You want to create AWS instances only for servers with valid IPs using for_each. Which expression correctly filters the map to exclude empty or null IPs?

hard

A. for_each = var.servers

B. for_each = { for k, v in var.servers : k => v if v != "" && v != null }

C. for_each = { for k, v in var.servers : k => v if v == "" || v == null }

D. for_each = [ for v in var.servers : v if v != "" ]

Solution

1. Step 1: Understand filtering with for expressions

   Use a for expression with an if condition to filter out empty strings and null values from the map.

2. Step 2: Check each option

   for_each = { for k, v in var.servers : k => v if v != "" && v != null } correctly filters keys where value is neither empty string nor null, producing a valid filtered map for for_each.

3. Final Answer:

   for_each = { for k, v in var.servers : k => v if v != "" && v != null } -> Option B

4. Quick Check:

   Filter map with if condition to exclude empty/null [OK]

Hint: Filter map with for and if to exclude empty/null [OK]

Common Mistakes:

• Not filtering out empty or null values
• Using list comprehension instead of map
• Filtering for empty/null instead of excluding them