Introduction:

This is a guide for creating an AWS CLI script that automates the deployment of an Application Load Balancer (ALB).
ALB will be configured with 2 Target Groups, each associated with a different EC2 instance.
The instances will run a basic web server with HTML content, each instance with a different path to distinguish between them.

I will be using the default VPC of the region, along with 2 default public subnets each in a different availability zone.

Before running the scripts: $ ./example-script.sh ,
give them permission to execute: $ chmod +x example-script.sh

AWS Architecture Diagram :

Steps:

First: Connecting AWS:

$ aws configure

Login with IAM user credentials (access/secret key) and configure default region name:

AWS Access Key ID [None]: accesskey
AWS Secret Access Key [None]: secretkey
Default region name [None]: us-west-2
Default output format [None]:

Step 1: Creating a Security Group:

• Allow inbound traffic on port 80 (HTTP).
• When creating EC2 instances, associated this security group with them.

Step 2: Creating a Load Balancer:

• Create an Application Load Balancer (ALB).
• Configure the ALB to use 2 public subnets, one for each availability zone.
• Associate the previously created security group with the ALB.

Step 3: Creating 2 Target Groups:

• Create 2 target groups, one for the "/red" path and the other for the "/blue" path, configure each target group to use HTTP on port 80.

Step 4: Creating 2 EC2 Instances:

• Launch 2 EC2 instances, one for each target group.
• Associate the previously created security group with the instances.
• Install and configure Ubuntu Server on each instance.
• Create an HTML file on each instance ("/var/www/html/index.html") with content indicating the color associated with the instance ("/red" or "/blue").

Step 5: Register EC2 instances with Target Groups

• Register each EC2 instance with its corresponding Target Group.
• Make sure the instances are in a running state.

Step 6: Creating 2 Listeners:

• Create a Listener on the Application Load Balancer (ALB) with rules for "/red" & "/blue" path.
• Associate each rule with the respective target group.

Last: Easy destroy all:

• Create a temp.conf file, here we store the variables(ID, ARN) created from our main file.
• Create a destroy-script.sh file, here we delete all we have created in the AWS Cloud.

Test:

• Verify the deployment by accessing the ALB's DNS name in a web browser and navigating to the "/red" and "/blue" paths.