Why expressions add logic in Terraform - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to use a conditional expression that sets the instance type to 't2.micro' if the environment is 'dev'.

Terraform

instance_type = var.environment == "dev" ? [1] : "t2.large"

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

A"t2.large"

B"t2.micro"

C"m5.large"

D"c5.xlarge"

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong instance type for the 'dev' environment.

Swapping the true and false parts of the conditional expression.

The conditional expression checks if the environment is 'dev'. If true, it sets the instance type to 't2.micro'. Otherwise, it uses 't2.large'.

2fill in blank

medium

Complete the code to set the number of instances to 3 if the region is 'us-east-1', otherwise 1.

Terraform

count = var.region == "us-east-1" ? [1] : 1

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

A3

B1

C5

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1 instead of 3 for the 'us-east-1' region.

Confusing the true and false values.

The expression sets 'count' to 3 when the region is 'us-east-1'. Otherwise, it sets 'count' to 1.

3fill in blank

hard

Fix the error in the expression that sets 'enable_monitoring' to true only if 'environment' is 'prod'.

Terraform

enable_monitoring = var.environment [1] "prod" ? true : false

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

A!=

B=

C=>

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using '=' instead of '==' for comparison.

Using '=>' which is not valid in this context.

The equality operator '==' is required to compare values in Terraform expressions. Using '=' causes an error.

4fill in blank

hard

Complete the code to create a conditional expression that sets 'storage_type' to 'gp2' if 'use_ssd' is true, otherwise 'standard'.

Terraform

storage_type = var.use_ssd [1] "gp2" : "standard"

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

A?

B:

C==

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' or '!=' instead of '?' and ':'.

Swapping the positions of '?' and ':'.

The conditional expression uses '?' after the condition and ':' before the else value. This sets 'storage_type' to 'gp2' if 'use_ssd' is true, else 'standard'.

5fill in blank

hard

Fill all three blanks to create a conditional expression that sets 'backup_enabled' to true if 'environment' is 'prod' and 'backup_window' is not empty, otherwise false.

Terraform

backup_enabled = var.environment [1] "prod" [2] var.backup_window [3] "" ? true : false

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

A==

B!=

C&&

D||

Attempts:

3 left

💡 Hint

Common Mistakes

Using '||' instead of '&&' which changes the logic.

Mixing up '==' and '!=' operators.

The expression checks if 'environment' equals 'prod' and 'backup_window' is not empty using '==' and '!=' operators combined with '&&' (and). If both are true, 'backup_enabled' is true; otherwise false.

Practice

1. What is the main purpose of a conditional expression (also called a "why expression") in Terraform?

easy

A. To define variables with fixed values

B. To create loops that repeat resources

C. To choose between two values based on a condition

D. To import external modules automatically

Solution

1. Step 1: Understand conditional expressions

   Conditional expressions let Terraform pick one of two values depending on a true or false condition.

2. Step 2: Compare with other Terraform features

   Loops repeat resources, variables hold values, and modules are imported differently, so they don't match the conditional expression purpose.

3. Final Answer:

   To choose between two values based on a condition -> Option C

4. Quick Check:

   Conditional expression = choose value [OK]

Hint: Conditional expressions pick values based on true/false [OK]

Common Mistakes:

• Confusing conditionals with loops
• Thinking conditionals define variables
• Mixing conditionals with module imports

2. Which of the following is the correct syntax for a Terraform conditional expression?

easy

A. condition ? true_value : false_value

B. if (condition) { true_value } else { false_value }

C. condition => true_value, false_value

D. switch(condition) { true_value, false_value }

Solution

1. Step 1: Recall Terraform conditional syntax

   Terraform uses the syntax: condition ? true_value : false_value for conditionals.

2. Step 2: Identify incorrect options

   Options A, C, and D use syntax styles from other languages or invalid formats not supported by Terraform.

3. Final Answer:

   condition ? true_value : false_value -> Option A

4. Quick Check:

   Terraform conditional = ? : syntax [OK]

Hint: Look for question mark and colon in conditional syntax [OK]

Common Mistakes:

• Using if-else blocks instead of ? :
• Confusing with arrow or switch syntax
• Missing colon or question mark

3. Given the Terraform expression: var.is_production ? "prod-server" : "dev-server", what will be the output if var.is_production is false?

medium

A. "dev-server"

B. "prod-server"

C. null

D. Error: invalid expression

Solution

1. Step 1: Evaluate the condition

   The condition is var.is_production, which is false in this case.

2. Step 2: Apply the conditional expression

   Since the condition is false, the expression returns the value after the colon, which is "dev-server".

3. Final Answer:

   "dev-server" -> Option A

4. Quick Check:

   False condition returns false_value [OK]

Hint: False condition returns value after colon [OK]

Common Mistakes:

• Choosing true_value instead of false_value
• Expecting null instead of false branch
• Thinking it causes an error

4. Identify the error in this Terraform conditional expression: count = var.enable_feature ? 1, 0

medium

A. Conditional expressions cannot be used for count

B. Missing colon between true and false values

C. Variable name is invalid

D. Using comma instead of question mark

Solution

1. Step 1: Check conditional expression syntax

   The correct syntax requires a colon ':' between true and false values, not a comma.

2. Step 2: Confirm other parts are valid

   Variable name and use for count are valid; only the separator is wrong.

3. Final Answer:

   Missing colon between true and false values -> Option B

4. Quick Check:

   Conditional needs ? and : separators [OK]

Hint: Use colon, not comma, between true and false parts [OK]

Common Mistakes:

• Using comma instead of colon
• Thinking count cannot use conditionals
• Assuming variable name is wrong

5. You want to create a resource with a name that depends on environment type. If var.env is "prod", use "server-prod", otherwise use "server-dev". Which expression correctly implements this logic?

hard

A. name = if var.env == "prod" then "server-prod" else "server-dev"

B. name = var.env ? "server-prod" : "server-dev"

C. name = var.env == "prod" : "server-prod" ? "server-dev"

D. name = var.env == "prod" ? "server-prod" : "server-dev"

Solution

1. Step 1: Check condition and syntax

   The condition must compare var.env to "prod" using ==, then use ? and : for true/false values.

2. Step 2: Validate each option

   name = var.env == "prod" ? "server-prod" : "server-dev" uses correct syntax. name = var.env ? "server-prod" : "server-dev" misses comparison. name = var.env == "prod" : "server-prod" ? "server-dev" swaps ? and :. name = if var.env == "prod" then "server-prod" else "server-dev" uses invalid if-then-else syntax in Terraform.

3. Final Answer:

   name = var.env == "prod" ? "server-prod" : "server-dev" -> Option D

4. Quick Check:

   Use == with ? : for conditionals [OK]

Hint: Compare with ==, then use ? : for true/false [OK]

Common Mistakes:

• Omitting comparison operator
• Swapping ? and : positions
• Using if-then-else syntax not supported