Auto Scaling with ELB integration in AWS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the launch configuration name in the Auto Scaling group.

AWS

resource "aws_autoscaling_group" "example" {
  launch_configuration = "[1]"
  min_size             = 1
  max_size             = 3
  vpc_zone_identifier  = ["subnet-12345678"]
}

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

Amy_launch_config

Bexample_asg

Cmy_elb

Dsubnet-12345678

Attempts:

3 left

💡 Hint

Common Mistakes

Using the Auto Scaling group name instead of the launch configuration name.

Using subnet ID instead of launch configuration.

The launch_configuration property must be set to the name of the launch configuration resource.

2fill in blank

medium

Complete the code to attach the Elastic Load Balancer to the Auto Scaling group.

AWS

resource "aws_autoscaling_group" "example" {
  launch_configuration = "my_launch_config"
  min_size             = 1
  max_size             = 3
  vpc_zone_identifier  = ["subnet-12345678"]
  [1] = ["my-elb"]
}

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

Alistener_arns

Belb_name

Ctarget_group_arns

Dload_balancers

Attempts:

3 left

💡 Hint

Common Mistakes

Using target_group_arns for classic ELB attachment.

Using incorrect attribute names.

The load_balancers property attaches classic ELBs to the Auto Scaling group.

3fill in blank

hard

Fix the error in the Auto Scaling group resource by completing the missing property for health check type.

AWS

resource "aws_autoscaling_group" "example" {
  launch_configuration = "my_launch_config"
  min_size             = 1
  max_size             = 3
  vpc_zone_identifier  = ["subnet-12345678"]
  load_balancers       = ["my-elb"]
  health_check_type    = "[1]"
}

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

AEC2

BELB

CAUTO

DTARGET

Attempts:

3 left

💡 Hint

Common Mistakes

Setting health_check_type to EC2 when using ELB.

Using invalid health check types.

When using an ELB, the health_check_type should be set to ELB to use the load balancer's health checks.

4fill in blank

hard

Fill both blanks to configure the Auto Scaling group with desired capacity and termination policies.

AWS

resource "aws_autoscaling_group" "example" {
  launch_configuration = "my_launch_config"
  min_size             = 1
  max_size             = 3
  desired_capacity     = [1]
  termination_policies = ["[2]"]
  vpc_zone_identifier  = ["subnet-12345678"]
  load_balancers       = ["my-elb"]
  health_check_type    = "ELB"
}

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

A2

BOldestInstance

CNewestInstance

DDefault

Attempts:

3 left

💡 Hint

Common Mistakes

Setting desired capacity outside min and max range.

Using invalid termination policy names.

The desired_capacity sets how many instances should run, here 2. The termination_policies define which instances to terminate first; OldestInstance is a common choice.

5fill in blank

hard

Fill all three blanks to define a launch configuration with AMI, instance type, and associate it with a security group.

AWS

resource "aws_launch_configuration" "my_launch_config" {
  name_prefix   = "example-"
  image_id      = "[1]"
  instance_type = "[2]"
  security_groups = ["[3]"]
}

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

Aami-0abcdef1234567890

Bt3.micro

Csg-0123456789abcdef0

Dsubnet-12345678

Attempts:

3 left

💡 Hint

Common Mistakes

Using subnet ID instead of security group ID.

Using invalid AMI or instance type values.

The image_id is the AMI ID to launch instances from. The instance_type defines the size of the instance. The security_groups list controls network access.

Practice

1. What is the main purpose of integrating an Auto Scaling group with an Elastic Load Balancer (ELB)?

easy

A. To distribute incoming traffic evenly across all running instances

B. To store data persistently across instances

C. To create backups of instances automatically

D. To monitor the health of the database

Solution

1. Step 1: Understand Auto Scaling and ELB roles

   Auto Scaling adjusts the number of servers based on demand. ELB distributes user traffic across these servers.

2. Step 2: Identify integration benefit

   Linking Auto Scaling with ELB ensures traffic is balanced only to healthy, running instances, improving availability.

3. Final Answer:

   To distribute incoming traffic evenly across all running instances -> Option A

4. Quick Check:

   Auto Scaling + ELB = balanced traffic [OK]

Hint: ELB balances traffic; Auto Scaling adjusts servers [OK]

Common Mistakes:

• Confusing ELB with storage or backup services
• Thinking Auto Scaling manages data persistence
• Assuming ELB monitors databases

2. Which of the following is the correct way to attach an Auto Scaling group to an ELB target group in AWS CLI?

easy

A. aws elb attach-instances --group-name my-asg --target-group-arn arn:aws:elasticloadbalancing:region:123456789012:targetgroup/my-target-group/abcdef123456

B. aws elb create-auto-scaling-group --name my-asg --target-group my-target-group

C. aws autoscaling create-target-group --name my-target-group --auto-scaling-group my-asg

D. aws autoscaling attach-load-balancer-target-groups --auto-scaling-group-name my-asg --target-group-arns arn:aws:elasticloadbalancing:region:123456789012:targetgroup/my-target-group/abcdef123456

Solution

1. Step 1: Identify correct AWS CLI command

   The command to attach an Auto Scaling group to an ELB target group is 'aws autoscaling attach-load-balancer-target-groups'.

2. Step 2: Verify command parameters

   It requires the Auto Scaling group name and the target group ARN, matching aws autoscaling attach-load-balancer-target-groups --auto-scaling-group-name my-asg --target-group-arns arn:aws:elasticloadbalancing:region:123456789012:targetgroup/my-target-group/abcdef123456.

3. Final Answer:

   aws autoscaling attach-load-balancer-target-groups --auto-scaling-group-name my-asg --target-group-arns arn:aws:elasticloadbalancing:region:123456789012:targetgroup/my-target-group/abcdef123456 -> Option D

4. Quick Check:

   Attach ASG to ELB target group uses attach-load-balancer-target-groups [OK]

Hint: Use 'attach-load-balancer-target-groups' with ASG name and target group ARN [OK]

Common Mistakes:

• Using ELB commands instead of Auto Scaling commands
• Confusing target group ARN with target group name
• Trying to create target groups via Auto Scaling CLI

3. Given this AWS Auto Scaling group configuration snippet:

{
  "AutoScalingGroupName": "web-asg",
  "TargetGroupARNs": ["arn:aws:elasticloadbalancing:region:123456789012:targetgroup/web-tg/abc123"],
  "MinSize": 2,
  "MaxSize": 4,
  "DesiredCapacity": 3
}

What happens when one instance fails health checks in the ELB target group?

medium

A. Auto Scaling terminates the unhealthy instance and launches a new one to maintain desired capacity

B. ELB stops sending traffic but Auto Scaling does not replace the instance

C. Auto Scaling increases MaxSize to 5 automatically

D. Nothing happens until manual intervention

Solution

1. Step 1: Understand health check integration

   When an instance fails ELB health checks, Auto Scaling detects it as unhealthy.

2. Step 2: Auto Scaling response

   Auto Scaling terminates the unhealthy instance and launches a new one to keep the desired capacity at 3.

3. Final Answer:

   Auto Scaling terminates the unhealthy instance and launches a new one to maintain desired capacity -> Option A

4. Quick Check:

   Unhealthy instance triggers replacement by Auto Scaling [OK]

Hint: Auto Scaling replaces unhealthy instances to keep desired capacity [OK]

Common Mistakes:

• Thinking ELB alone replaces instances
• Assuming MaxSize changes automatically
• Believing manual steps are needed

4. You configured an Auto Scaling group with an ELB target group, but new instances are not receiving traffic. What is the most likely cause?

medium

A. The ELB is in a different AWS region than the Auto Scaling group

B. The Auto Scaling group has MinSize set to zero

C. The instances are not registered with the ELB target group

D. The instances do not have public IP addresses

Solution

1. Step 1: Check ELB and Auto Scaling integration

   If instances are not registered with the ELB target group, ELB cannot send traffic to them.

2. Step 2: Evaluate other options

   MinSize zero means no instances; region mismatch prevents communication; public IP not required for ELB internal routing.

3. Final Answer:

   The instances are not registered with the ELB target group -> Option C

4. Quick Check:

   Instances must be registered with ELB target group to get traffic [OK]

Hint: Check instance registration in ELB target group first [OK]

Common Mistakes:

• Assuming public IP is required for ELB traffic
• Ignoring instance registration status
• Confusing region mismatch with availability zone issues

5. You want to ensure your Auto Scaling group scales out only when the average CPU usage across all instances exceeds 70%, and also that new instances are healthy in the ELB before receiving traffic. Which combination of settings achieves this?

hard

A. Configure scaling policy on network traffic, and skip ELB health checks

B. Create a scaling policy based on CPU > 70%, enable ELB health checks with grace period

C. Use ELB health checks only, no CPU-based scaling policy

D. Set MinSize to 0, MaxSize to 10, and disable ELB health checks

Solution

1. Step 1: Define scaling trigger

   Scaling based on average CPU > 70% ensures scale out matches demand.

2. Step 2: Ensure instance health before traffic

   Enabling ELB health checks with a grace period lets new instances become healthy before receiving traffic.

3. Step 3: Combine both for smooth scaling

   This combination prevents traffic to unhealthy instances and scales only when needed.

4. Final Answer:

   Create a scaling policy based on CPU > 70%, enable ELB health checks with grace period -> Option B

5. Quick Check:

   CPU scaling + ELB health checks = safe, demand-based scaling [OK]

Hint: Combine CPU scaling policy with ELB health checks and grace period [OK]

Common Mistakes:

• Disabling ELB health checks causing traffic to unhealthy instances
• Using wrong metric like network traffic for CPU-based scaling
• Not setting grace period causing premature traffic routing