Preconditions and postconditions in Terraform - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a precondition that checks if the variable 'instance_count' is greater than zero.

Terraform

variable "instance_count" {
  type = number
  [1] = [
    {
      condition     = var.instance_count > 0
      error_message = "Instance count must be greater than zero."
    }
  ]
}

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

Aprecondition

Bpostcondition

Cvalidation

Dconstraint

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'precondition' or 'postcondition' inside variable blocks instead of 'validation'.

Placing the condition outside the variable block.

The validation block is used in Terraform variables to define preconditions that must be met before applying the configuration.

2fill in blank

medium

Complete the resource block to add a precondition that ensures the 'ami' attribute is not empty.

Terraform

resource "aws_instance" "example" {
  ami           = var.ami
  instance_type = "t2.micro"

  [1] {
    condition     = length(self.ami) > 0
    error_message = "AMI must not be empty."
  }
}

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

Apostcondition

Bvalidation

Cconstraint

Dprecondition

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'validation' inside resource blocks (only valid in variables).

Using 'postcondition' instead of 'precondition' for input checks.

The precondition block inside a resource checks conditions before creating or updating the resource.

3fill in blank

hard

Fix the error in the postcondition block that checks if the instance state is 'running'.

Terraform

resource "aws_instance" "example" {
  ami           = var.ami
  instance_type = "t2.micro"

  lifecycle {
    [1] {
      condition     = self.instance_state.name == "running"
      error_message = "Instance must be running after creation."
    }
  }
}

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

Aprecondition

Bpostcondition

Cvalidation

Dconstraint

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'precondition' inside lifecycle blocks.

Using 'validation' inside lifecycle blocks.

The postcondition block inside the lifecycle block checks conditions after resource creation or update.

4fill in blank

hard

Fill both blanks to add a precondition and a postcondition to a resource that checks 'instance_type' before creation and 'state' after creation.

Terraform

resource "aws_instance" "example" {
  ami           = var.ami
  instance_type = var.instance_type

  [1] {
    condition     = self.instance_type == "t2.micro"
    error_message = "Instance type must be t2.micro."
  }

  lifecycle {
    [2] {
      condition     = self.instance_state.name == "running"
      error_message = "Instance must be running after creation."
    }
  }
}

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

Aprecondition

Bvalidation

Cpostcondition

Dconstraint

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping precondition and postcondition blocks.

Using 'validation' inside resource blocks.

The precondition block checks conditions before resource creation, and the postcondition block inside lifecycle checks after creation.

5fill in blank

hard

Fill all three blanks to add a variable with validation, a resource with precondition, and a lifecycle postcondition.

Terraform

variable "region" {
  type = string
  [1] = [
    {
      condition     = var.region != ""
      error_message = "Region cannot be empty."
    }
  ]
}

resource "aws_instance" "example" {
  ami           = var.ami
  instance_type = "t2.micro"

  [2] {
    condition     = self.instance_type == "t2.micro"
    error_message = "Instance type must be t2.micro."
  }

  lifecycle {
    [3] {
      condition     = self.instance_state.name == "running"
      error_message = "Instance must be running after creation."
    }
  }
}

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

Avalidation

Bprecondition

Cpostcondition

Dconstraint

Attempts:

3 left

💡 Hint

Common Mistakes

Using precondition inside variable blocks.

Using validation inside resource blocks.

Placing postcondition outside lifecycle.

Variables use validation blocks for input checks. Resources use precondition blocks before creation and postcondition blocks inside lifecycle after creation.