Plan and apply separation in pipelines in Terraform - Mini Project: Build & Apply

Plan and apply separation in pipelines

📖 Scenario: You are working in a team managing cloud infrastructure using Terraform. To keep your deployment process safe and organized, you want to separate the planning and applying steps into two different pipeline stages. This helps catch errors before making changes live.

🎯 Goal: Build a Terraform pipeline configuration that clearly separates the terraform plan step from the terraform apply step using two distinct pipeline jobs.

📋 What You'll Learn

Create a Terraform pipeline with two jobs: plan and apply

The plan job runs terraform init and terraform plan

The apply job runs terraform apply only after plan succeeds

Use a variable to control the Terraform workspace name

💡 Why This Matters

🌍 Real World

Separating plan and apply steps in Terraform pipelines is a common practice in real-world cloud infrastructure management to prevent accidental changes and improve safety.

💼 Career

Cloud engineers and DevOps professionals use this pattern daily to maintain reliable and controlled infrastructure deployments.

1

Define Terraform workspace variable

Create a Terraform variable called workspace with default value dev in a file named variables.tf. This variable will hold the workspace name.

Terraform

# Your code here

Hint

Use the variable block with a default value.

2

Create plan job configuration

Add a pipeline job named plan that runs terraform init and terraform plan using the workspace variable var.workspace. Use a shell script block for commands.

Terraform

variable "workspace" {
  description = "The Terraform workspace name"
  type        = string
  default     = "dev"
}

# Your code here

Hint

Define a job block with steps running terraform init and terraform plan using the variable.

3

Create apply job with dependency

Add a pipeline job named apply that runs terraform apply -auto-approve using the workspace variable var.workspace. Make sure this job depends on the plan job so it runs only after planning succeeds.

Terraform

variable "workspace" {
  description = "The Terraform workspace name"
  type        = string
  default     = "dev"
}

job "plan" {
  steps = [
    "terraform init",
    "terraform plan -var='workspace=${var.workspace}'"
  ]
}

# Your code here

Hint

Use depends_on to link the apply job to plan.

4

Complete pipeline with workspace usage

Ensure the pipeline uses the workspace variable in both jobs and that the apply job runs only after the plan job completes successfully. The final pipeline configuration should include the variable and both jobs with correct commands and dependencies.

Terraform

variable "workspace" {
  description = "The Terraform workspace name"
  type        = string
  default     = "dev"
}

job "plan" {
  steps = [
    "terraform init",
    "terraform plan -var='workspace=${var.workspace}'"
  ]
}

job "apply" {
  depends_on = ["plan"]
  steps = [
    "terraform apply -auto-approve -var='workspace=${var.workspace}'"
  ]
}

# Your code here

Hint

Review that both jobs use the workspace variable and apply depends on plan.

Practice

1. What is the main benefit of separating terraform plan and terraform apply in pipelines?

easy

A. It speeds up the deployment by combining steps

B. It skips the need for state files

C. It automatically fixes errors during apply

D. It allows you to review changes before applying them

Solution

1. Step 1: Understand the purpose of terraform plan

   This command shows what changes Terraform will make without applying them.

2. Step 2: Understand the purpose of terraform apply

   This command applies the changes to the infrastructure based on the plan.

3. Final Answer:

   It allows you to review changes before applying them -> Option D

4. Quick Check:

   Plan shows changes first = B [OK]

Hint: Plan shows changes, apply makes them live [OK]

Common Mistakes:

• Thinking plan applies changes
• Believing apply skips state files
• Assuming steps run faster combined

2. Which command correctly saves a Terraform plan to a file named myplan.tfplan?

easy

A. terraform apply -out=myplan.tfplan

B. terraform save myplan.tfplan

C. terraform plan -out=myplan.tfplan

D. terraform plan save myplan.tfplan

Solution

1. Step 1: Identify the correct syntax for saving a plan

   The correct command uses terraform plan -out=filename to save the plan.

2. Step 2: Check each option

   terraform plan -out=myplan.tfplan matches the correct syntax exactly.

3. Final Answer:

   terraform plan -out=myplan.tfplan -> Option C

4. Quick Check:

   Plan with -out saves file = C [OK]

Hint: Use 'plan -out=' to save plans, not apply [OK]

Common Mistakes:

• Using apply instead of plan to save
• Using incorrect command like 'save'
• Missing the '-out=' flag

3. Given these commands run in order:
terraform plan -out=planfile
terraform apply planfile
What happens when you run terraform apply planfile?

medium

A. Terraform applies exactly the changes saved in planfile

B. Terraform ignores planfile and creates a new plan

C. Terraform applies changes but may differ from planfile

D. Terraform throws an error because planfile is not a valid command

Solution

1. Step 1: Understand the role of the saved plan file

   The plan file contains the exact changes Terraform will apply.

2. Step 2: Understand how terraform apply planfile works

   This command applies the saved plan exactly, without recalculating changes.

3. Final Answer:

   Terraform applies exactly the changes saved in planfile -> Option A

4. Quick Check:

   Apply saved plan = exact changes [OK]

Hint: Apply with plan file applies exact saved changes [OK]

Common Mistakes:

• Thinking apply recalculates plan
• Assuming apply ignores plan file
• Believing apply with plan file causes errors

4. You run terraform apply myplan.tfplan but get an error saying the plan file is invalid. What is the most likely cause?

medium

A. You forgot to run terraform init before apply

B. The plan file was created with a different Terraform version

C. You used terraform plan without -out flag

D. The plan file is empty because no changes were detected

Solution

1. Step 1: Identify compatibility issues with plan files

   Plan files are version-specific and may be invalid if Terraform versions differ.

2. Step 2: Check other options

   Running init is required but usually causes different errors; missing -out means no plan file saved; empty plan files do not cause invalid file errors.

3. Final Answer:

   The plan file was created with a different Terraform version -> Option B

4. Quick Check:

   Version mismatch causes invalid plan file error [OK]

Hint: Check Terraform versions match when using saved plans [OK]

Common Mistakes:

• Assuming missing init causes invalid plan file error
• Thinking empty plan files cause invalid file errors
• Confusing missing -out with invalid plan file

5. You want to implement a pipeline that separates planning and applying Terraform changes. Which sequence of commands ensures you can review the plan before applying exactly those changes?

hard

A. terraform plan -out=planfile && terraform apply planfile

B. terraform apply && terraform plan -out=planfile

C. terraform plan && terraform apply

D. terraform apply -out=planfile && terraform apply planfile

Solution

1. Step 1: Identify correct order for plan and apply separation

   First, run terraform plan -out=planfile to save the plan and review it.

2. Step 2: Apply the saved plan exactly

   Then, run terraform apply planfile to apply the reviewed changes exactly.

3. Final Answer:

   terraform plan -out=planfile && terraform apply planfile -> Option A

4. Quick Check:

   Plan with -out then apply saved plan = A [OK]

Hint: Plan with -out then apply saved plan file [OK]

Common Mistakes:

• Applying before planning
• Not saving plan with -out
• Using apply -out which is invalid