Blue-green infrastructure pattern in Terraform - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define the active environment variable for blue-green deployment.

Terraform

variable "active_environment" {
  type    = string
  default = "[1]"
}

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

Ablue

Bgreen

Cred

Dyellow

Attempts:

3 left

💡 Hint

Common Mistakes

Setting the default to an undefined environment like "red" or "yellow".

Leaving the default empty.

The default active environment is set to "blue" to start the blue-green deployment.

2fill in blank

medium

Complete the code to create a resource group for the green environment.

Terraform

resource "azurerm_resource_group" "green" {
  name     = "rg-[1]"
  location = var.location
}

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

Aprod

Bgreen

Cblue

Dtest

Attempts:

3 left

💡 Hint

Common Mistakes

Using "blue" instead of "green" for the green environment resource group.

Using unrelated names like "prod" or "test".

The resource group name includes "green" to represent the green environment.

3fill in blank

hard

Fix the error in the code to select the inactive environment correctly.

Terraform

locals {
  inactive_environment = var.active_environment == "blue" ? "[1]" : "blue"
}

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

Agreen

Bblue

Cprod

Dtest

Attempts:

3 left

💡 Hint

Common Mistakes

Setting inactive environment to "blue" when active is "blue".

Using unrelated environment names.

If the active environment is "blue", the inactive one should be "green" for blue-green deployment.

4fill in blank

hard

Fill both blanks to define the load balancer backend pool for the active environment.

Terraform

resource "azurerm_lb_backend_address_pool" "active_pool" {
  name                = "lb-backend-[1]"
  resource_group_name = azurerm_resource_group.[2].name
  loadbalancer_id     = azurerm_lb.main.id
}

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

Aactive_environment

Bgreen

Cblue

Dinactive_environment

Attempts:

3 left

💡 Hint

Common Mistakes

Using inactive environment name in the backend pool.

Referencing the resource group incorrectly.

The backend pool name uses the active environment name ("blue"), and the resource group name is referenced from the active environment variable.

5fill in blank

hard

Fill all three blanks to switch traffic to the inactive environment by updating the active environment variable and resource group references.

Terraform

variable "active_environment" {
  default = "[1]"
}

resource "azurerm_resource_group" "[2]" {
  name     = "rg-[3]"
  location = var.location
}

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

Agreen

Bblue

Attempts:

3 left

💡 Hint

Common Mistakes

Not updating the active environment variable.

Mismatching resource group names.

To switch traffic, set the active environment variable to "green" and create the resource group for "green" environment.

Practice

1. What is the main purpose of the blue-green infrastructure pattern in Terraform deployments?

easy

A. To reduce infrastructure costs by using a single environment

B. To automate database backups during deployment

C. To increase the number of servers in a single environment

D. To avoid downtime by switching traffic between two identical environments

Solution

1. Step 1: Understand the blue-green pattern concept

   The blue-green pattern uses two identical environments to ensure zero downtime during updates.

2. Step 2: Identify the main goal in Terraform deployments

   Terraform manages these environments and switches traffic between them to avoid downtime.

3. Final Answer:

   To avoid downtime by switching traffic between two identical environments -> Option D

4. Quick Check:

   Blue-green pattern = avoid downtime [OK]

Hint: Remember: blue-green means two environments for zero downtime [OK]

Common Mistakes:

• Thinking it reduces costs by using one environment
• Confusing it with scaling servers in one environment
• Assuming it automates backups

2. Which Terraform resource is commonly used to switch traffic between blue and green environments in a blue-green deployment?

easy

A. aws_lb_listener_rule

B. aws_instance

C. aws_s3_bucket

D. aws_security_group

Solution

1. Step 1: Identify Terraform resources related to traffic routing

   Load balancer listener rules control how traffic is routed to target groups.

2. Step 2: Match resource to blue-green traffic switch

   The aws_lb_listener_rule resource allows switching traffic between blue and green target groups.

3. Final Answer:

   aws_lb_listener_rule -> Option A

4. Quick Check:

   Traffic switch uses listener rules [OK]

Hint: Traffic routing uses listener rules, not instances or buckets [OK]

Common Mistakes:

• Choosing aws_instance which manages servers, not traffic
• Selecting aws_s3_bucket which is for storage
• Picking aws_security_group which controls firewall rules

3. Given this Terraform snippet for blue-green deployment traffic switching:

resource "aws_lb_listener_rule" "blue" {
  listener_arn = aws_lb_listener.front_end.arn
  priority     = 10
  action {
    type             = "forward"
    target_group_arn = aws_lb_target_group.blue.arn
  }
  condition {
    path_pattern {
      values = ["/blue/*"]
    }
  }
}

resource "aws_lb_listener_rule" "green" {
  listener_arn = aws_lb_listener.front_end.arn
  priority     = 20
  action {
    type             = "forward"
    target_group_arn = aws_lb_target_group.green.arn
  }
  condition {
    path_pattern {
      values = ["/green/*"]
    }
  }
}

What happens when a user visits /green/home?

medium

A. Traffic is routed to the green target group

B. Traffic is routed to both blue and green target groups

C. Traffic is blocked by the load balancer

D. Traffic is routed to the blue target group

Solution

1. Step 1: Analyze path pattern conditions in listener rules

   The green listener rule matches paths starting with /green/* and forwards to the green target group.

2. Step 2: Match user request path to rules

   The request /green/home matches the green rule condition, so traffic goes to the green target group.

3. Final Answer:

   Traffic is routed to the green target group -> Option A

4. Quick Check:

   Path /green/* routes to green group [OK]

Hint: Match URL path to listener rule path pattern [OK]

Common Mistakes:

• Assuming default routing to blue group
• Thinking traffic is blocked without default rule
• Believing traffic splits between groups

4. You wrote this Terraform code to switch traffic in a blue-green setup but the traffic does not switch as expected:

resource "aws_lb_listener_rule" "blue" {
  listener_arn = aws_lb_listener.front_end.arn
  priority     = 10
  action {
    type             = "forward"
    target_group_arn = aws_lb_target_group.blue.arn
  }
  condition {
    host_header {
      values = ["blue.example.com"]
    }
  }
}

resource "aws_lb_listener_rule" "green" {
  listener_arn = aws_lb_listener.front_end.arn
  priority     = 10
  action {
    type             = "forward"
    target_group_arn = aws_lb_target_group.green.arn
  }
  condition {
    host_header {
      values = ["green.example.com"]
    }
  }
}

What is the likely problem?

medium

A. Target groups are not defined correctly

B. Host header condition is invalid for load balancers

C. Both listener rules have the same priority, causing conflict

D. Listener ARN is missing in one of the rules

Solution

1. Step 1: Check listener rule priorities

   Both rules have priority 10, which causes a conflict because priorities must be unique.

2. Step 2: Understand effect of priority conflict

   Load balancer cannot decide which rule to apply, so traffic routing fails or is unpredictable.

3. Final Answer:

   Both listener rules have the same priority, causing conflict -> Option C

4. Quick Check:

   Unique priorities required for listener rules [OK]

Hint: Listener rule priorities must be unique numbers [OK]

Common Mistakes:

• Ignoring priority uniqueness
• Assuming host_header condition is invalid
• Overlooking target group correctness

5. You want to implement a blue-green deployment in Terraform with minimal downtime. Which approach best achieves this?

hard

A. Deploy new version to green environment and keep routing traffic to blue until green is manually deleted

B. Deploy new version to green environment, test it, then update load balancer to route all traffic to green

C. Deploy new version directly to blue environment and restart all servers simultaneously

D. Deploy new version to blue environment and use DNS TTL to switch traffic slowly

Solution

1. Step 1: Understand blue-green deployment goals

   The goal is zero downtime by having two identical environments and switching traffic atomically.

2. Step 2: Evaluate deployment approaches

   Deploying to green, testing, then switching load balancer traffic ensures smooth transition without downtime.

3. Step 3: Compare other options

   Direct deploy with restart causes downtime; manual deletion delays switch; DNS TTL causes slow switch and possible downtime.

4. Final Answer:

   Deploy new version to green environment, test it, then update load balancer to route all traffic to green -> Option B

5. Quick Check:

   Blue-green = test new env, then switch traffic [OK]

Hint: Test new environment fully before switching traffic [OK]

Common Mistakes:

• Restarting servers causing downtime
• Delaying traffic switch by manual deletion
• Relying on DNS TTL for instant switch