AWS Application Load Balancer Basics with Terraform

Step-01: Introduction

• Create AWS ALB Application Load Balancer Terraform Module
• Re-use AWS Security Group created for Load Balancers

Step-02: Create ALB Basic Manually

Step-02-01: Create EC2 Instance with Userdata

• Go to AWS Services -> EC2 -> Instances -> Launch Instances
• Step 1: Choose an Amazon Machine Image (AMI): Amazon Linux 2 AMI (HVM), SSD Volume Type
• Step 2: Choose an Instance Type: t2.micro
• Step 3: Configure Instance Details:
  • Number of Instances: 2
  • Userdata: select file and reference terraform-manifests/app1-install.sh for userdata
  • Rest all defaults
• Step 4: Add Storage: leave to defaults
• Step 5: Add Tags:
  • Key: Name
  • Value: ALB-Manual-Test-1
• Step 6: Configure Security Group:
  • Security Group Name: ALB-Manual-TestSG1
  • Add SSH and HTTP rules for entire internet edge 0.0.0.0/0
• Step 7: Review Instance Launch: Click on Launch
• Select an existing key pair or create a new key pair: terraform-key
• Click on Launch Instance
• Verify once the EC2 Instance is created and wait for Instances to be in 2/2 checks passed
• Access Instances and verify

# Access App1 from both Instances
http://<public-ip-instance-1>/app1/index.html
http://<public-ip-instance-1>/app1/metadata.html
http://<public-ip-instance-2>/app1/index.html
http://<public-ip-instance-2>/app1/metadata.html

Step-02-02: Create Target Group

• Go to AWS Services -> EC2 -> Target Groups -> Create target group
• Choose a target type: Instances
• Target Group Name: app1-tg
• Protocol: HTTP
• Port: 80
• VPC: default-vpc
• Protocol Version: HTTP1
• Health Check Protocol: HTTP
• Health check path: /app1/index.html
• Advanced Health Check Settings - Port: Traffic Port
• Healthy threshold: 5
• Unhealthy threshold: 2
• Timeout: 5 seconds
• Interval: 30 seconds
• Success codes: 200-399
• Tags: App = app1-tg
• Click Next
• Register targets
  • Select EC2 Instances: select EC2 Instances
  • Ports for the selected instances: 80
  • Click on Include as pending below
• Click on Create target group

Step-02-03: Create Application Load Balancer

• Go to AWS Services -> EC2 -> Load Balancing -> Load Balancers -> Create Load Balancer
• Select load balancer type: Application Load Balancer
• Step 1: Configure Load Balancer
  • Name: alb-basic-test
  • Scheme: internet-facing
  • IP address type: ipv4
  • Listeners:
    • Load Balancer Protocol: HTTP
    • Load Balancer Port: 80
  • Availability Zones:
    • VPC: default-vpc
    • Availability Zones: us-east-1a, us-east-1b, us-east-1c (Verify first where EC2 Instances created)
• Step 2: Configure Security Settings
  • Click Next
• Step 3: Configure Security Groups
  • Assign a security group: create new security group
  • Security group name: loadbalancer-alb-sg
  • Rule: HTTP Port 80 from internet 0.0.0.0/0
• Step 4: Configure Routing
  • Target group: Existing Target Group
  • Name: app1-tg
  • Click Next
• Step 5: Register Targets
  • Click Next Review
• Step 6: Review Click on Create

Step-02-04: Verify the following

• Wait for Load Balancer to be in active state
• Verify ALB Load Balancer
  • Description Tab
  • Listeners Tab
  • Listeners Tab -> Rules
• Verify Target Groups
  • They should be in HEALTHY
• Access using Load Balancer DNS

# Access Application
http://alb-basic-test-1565875067.us-east-1.elb.amazonaws.com
http://alb-basic-test-1565875067.us-east-1.elb.amazonaws.com/app1/index.html
http://alb-basic-test-1565875067.us-east-1.elb.amazonaws.com/app1/metadata.html

Step-02-05: Clean-Up

• Delete Load Balacner
• Delete Target Groups
• Delete EC2 Instances

Step-03: Copy all files from previous section

• We are going to copy all files from previous section 08-AWS-ELB-Classic-LoadBalancer
• Files from c1 to c9
• Create the files for ALB Basic
  • c10-01-ALB-application-loadbalancer-variables.tf
  • c10-02-ALB-application-loadbalancer.tf
  • c10-03-ALB-application-loadbalancer-outputs.tf

Step-04: c10-02-ALB-application-loadbalancer.tf

• Create AWS Application Load Balancer Terraform configuration using ALB Terraform Module

# Terraform AWS Application Load Balancer (ALB)
module "alb" {
  source  = "terraform-aws-modules/alb/aws"
  #version = "5.16.0"
  version = "9.3.0"

  name = "${local.name}-alb"
  load_balancer_type = "application"
  vpc_id = module.vpc.vpc_id
  subnets = module.vpc.public_subnets
  #security_groups = [module.loadbalancer_sg.this_security_group_id]
  security_groups = [module.loadbalancer_sg.security_group_id]

  # For example only
  enable_deletion_protection = false

# Listeners
  listeners = {
    # Listener-1: my-http-listener
    my-http-listener = {
      port     = 80
      protocol = "HTTP"
      forward = {
        target_group_key = "mytg1"
      }         
    }# End of my-http-listener
  }# End of listeners block

# Target Groups
  target_groups = {
   # Target Group-1: mytg1     
   mytg1 = {
      # VERY IMPORTANT: We will create aws_lb_target_group_attachment resource separately when we use create_attachment = false, refer above GitHub issue URL.
      ## Github ISSUE: https://github.com/terraform-aws-modules/terraform-aws-alb/issues/316
      ## Search for "create_attachment" to jump to that Github issue solution
      create_attachment = false
      name_prefix                       = "mytg1-"
      protocol                          = "HTTP"
      port                              = 80
      target_type                       = "instance"
      deregistration_delay              = 10
      load_balancing_cross_zone_enabled = false
      protocol_version = "HTTP1"
      health_check = {
        enabled             = true
        interval            = 30
        path                = "/app1/index.html"
        port                = "traffic-port"
        healthy_threshold   = 3
        unhealthy_threshold = 3
        timeout             = 6
        protocol            = "HTTP"
        matcher             = "200-399"
      }# End of health_check Block
      tags = local.common_tags # Target Group Tags 
    } # END of Target Group: mytg1
  } # END OF target_groups Block
  tags = local.common_tags # ALB Tags
}

# Load Balancer Target Group Attachment
resource "aws_lb_target_group_attachment" "mytg1" {
  for_each = {for k, v in module.ec2_private: k => v}
  target_group_arn = module.alb.target_groups["mytg1"].arn
  target_id        = each.value.id
  port             = 80
}

## k = ec2_instance
## v = ec2_instance_details

## TEMP App Outputs
output "zz_ec2_private" {
  #value = {for k, v in module.ec2_private: k => v}
  value = {for ec2_instance, ec2_instance_details in module.ec2_private: ec2_instance => ec2_instance_details}
}

Step-05: c10-03-ALB-application-loadbalancer-outputs.tf

# Terraform AWS Application Load Balancer (ALB) Outputs
################################################################################
# Load Balancer
################################################################################

output "id" {
  description = "The ID and ARN of the load balancer we created"
  value       = module.alb.id
}

output "arn" {
  description = "The ID and ARN of the load balancer we created"
  value       = module.alb.arn
}

output "arn_suffix" {
  description = "ARN suffix of our load balancer - can be used with CloudWatch"
  value       = module.alb.arn_suffix
}

output "dns_name" {
  description = "The DNS name of the load balancer"
  value       = module.alb.dns_name
}

output "zone_id" {
  description = "The zone_id of the load balancer to assist with creating DNS records"
  value       = module.alb.zone_id
}

################################################################################
# Listener(s)
################################################################################

output "listeners" {
  description = "Map of listeners created and their attributes"
  value       = module.alb.listeners
  sensitive   = true
}

output "listener_rules" {
  description = "Map of listeners rules created and their attributes"
  value       = module.alb.listener_rules
  sensitive   = true
}

################################################################################
# Target Group(s)
################################################################################

output "target_groups" {
  description = "Map of target groups created and their attributes"
  value       = module.alb.target_groups
}

Step-06: Execute Terraform Commands

# Terraform Initialize
terraform init

# Terraform Validate
terraform validate

# Terraform Plan
terraform plan

# Terraform Apply
terraform apply -auto-approve

# Verify
Observation: 
1. Verify EC2 Instances
2. Verify Load Balancer SG
3. Verify ALB Listeners and Rules
4. Verify ALB Target Groups, Targets (should be healthy) and Health Check settings
5. Access sample app using Load Balancer DNS Name
# Example: from my environment
http://hr-stag-alb-1575108738.us-east-1.elb.amazonaws.com 
http://hr-stag-alb-1575108738.us-east-1.elb.amazonaws.com/app1/index.html
http://hr-stag-alb-1575108738.us-east-1.elb.amazonaws.com/app1/metadata.html

Step-07: Clean-Up

# Terraform Destroy
terraform destroy -auto-approve

# Delete files
rm -rf .terraform*
rm -rf terraform.tfstate*