Amazon EC2 allows us to create virtual machines, or instances, that run on the AWS Cloud .

How to create , manage & connect to an EC2 instance ?

search for EC2 in the search box
Now select The Option Virtual Servers in Cloud to view EC2 Dashboard.
In the EC2 Dashboard we will set to see a section called Launch Instance
To Launch an instance press Launch instance:
- In order to connect to this server remotely Create new key pair.
  - fill in the required details:
- Save the .pem or .ppk file that gets generated.
Once configuring the server according to Our needs Click on Launch Instance.
Now to connect to the Server click on the Instance ID and then click on connect.
Now Follow the steps that are mentioned:

Now to connect the instance remotely:

Locate your private key file (usually in Downloads folder)

ensure your key in not publicly viewable:

 cd Downlloads
 ls -l
 total 1
 -rw-r--r--@  1 root  group     1674 Dec  3 19:41 Test-server-RSA-Privet-key.pem
 # to change the visibility
 chmod 400 Test-server-RSA-Privet-key.pem
 ls -l
 total 1
 -r--------@  1 root  group     1674 Dec  3 19:41 Test-server-RSA-Privet-key.pem

Now to connect to the instance remotely run the following command in the terminal:

  ssh -i "Test-server-RSA-Privet-key.pem" ubuntu@ec2-3-81-19-167.compute-1.amazonaws.com

Launch Templates:

In order to avoid repeating the above tasks we can create a Template from instance.
Configure the template according to your needs:
No to use this template:
- navigate to launch templates then select the template and toggle Actions button to view launch instance from template.
The instance will be preconfigured and to launch a new instance just click on create instance :

User Data Script (EC2) :

In order to configure the EC2 instance with updates, other services ect we use user data script:
scroll to the bottom of launch instance from template page and you will get to see advance options , toggle it and again scroll down to see the following result:

this user data will apply for the current instances begin created using the instance template and will not persist .

we might need to add the user data if we intend to use this instance again.

To avoid this we can modify the instance template
Modify the Instance Template:

scroll down and toggle Advanced Option and then again scroll down :

Suppose we want to update the Instance and also want to install tools like docker , nginx then we can write a user data which is actually a bash file

  #!/bin/bash
  sudo apt-get update -y
  sudo apt-get install docker.io -y
  sudo apt-get install git-all -y
  sudo apt update
  sudo apt install fontconfig openjdk-17-jre -y
  java -version
  openjdk version "17.0.8" 2023-07-18
  OpenJDK Runtime Environment (build 17.0.8+7-Debian-1deb12u1)
  OpenJDK 64-Bit Server VM (build 17.0.8+7-Debian-1deb12u1, mixed mode, sharing) 
  sudo wget -O /usr/share/keyrings/jenkins-keyring.asc \
    https://pkg.jenkins.io/debian-stable/jenkins.io-2023.key
  echo deb [signed-by=/usr/share/keyrings/jenkins-keyring.asc] \
    https://pkg.jenkins.io/debian-stable binary/ | sudo tee \
    /etc/apt/sources.list.d/jenkins.list > /dev/null
  sudo apt-get update
  sudo apt-get install jenkins -y

  sudo usermod -aG docker ubuntu
  sudo usermod -aG docker jenkins
  sudo apt-get upgrate -y

Autoscaling & Load Balancing:

Autoscaling and load balancing are crucial components in a system's architecture to ensure optimal performance, availability, and cost efficiency

Scenario: E-commerce Website on Amazon EC2

Imagine you have an e-commerce website hosted on Amazon EC2 instances.

Normal Traffic:

During regular hours, your website experiences moderate traffic.
You have a fixed number of EC2 instances handling the incoming requests.
Everything works smoothly, and users can browse and make purchases without any noticeable delays

Traffic Surge:

Suddenly, a marketing campaign or a flash sale results in a significant increase in traffic.
The current number of EC2 instances may struggle to handle the sudden surge, leading to slower response times or, in worst cases, service outages.

Need For Autoscaling :

Autoscaling allows your infrastructure to automatically respond to changes in demand.
When the traffic increases, autoscaling can spin up additional EC2 instances to handle the load.
During periods of low traffic, autoscaling can reduce the number of instances, ensuring that you're not paying for resources you don't need.

Uneven Distribution 🤔:
- Assuming autoscaling is in place, new instances are spun up to accommodate the increased traffic.
- However, without load balancing, all incoming requests might be directed to a single instance (or a few instances), leading to uneven distribution of the load.

Need For Load Balancing:

Load balancing distributes incoming network traffic across multiple EC2 instances, ensuring that no single instance bears the entire burden.

This improves responsiveness and prevents any individual instance from becoming a bottleneck.

Traffic Decrease:

After the surge, the traffic returns to normal levels.
Autoscaling can now scale down the number of instances to save on costs, ensuring that you're not over-provisioned during quieter periods.

Implementing Auto Scaling groups and Load Balancing :

An Auto Scaling group is a collection of Amazon EC2 instances that are treated as a logical unit.
Make Sure that you Don't include subnet in launch template because it is Not applicable for EC2 Auto Scaling.
Also Shutdown behavior, Stop - Hibernate behavior like Stop and Terminate are Not applicable for EC2 Auto Scaling.
Navigate to EC2 and In the left panel scroll to the bottom until you find the Auto Scaling toggle button.
Now to create an Auto Scaling group Click 'Create Auto Scaling group' :
Now give a name to the Auto Scaling group and select the launch template with the proper template version if you have multiple versions available:
In the next step we need to Choose instance launch options:
- Select the subnets that you want your instance to run on.

Configure advanced options:

Attaching a Load balancing:
- Configure group size and scaling:
  
  Set this according to the needs.
- Add Notification if you want:
- Add Tags
- Review:
When we click create Auto Scaling group.
- you can observe that whenever the CPU performance (i selected it) exceeds the threshold value then it will trigger the build of new EC2 instance .