AWS Classroomnotes 29/Apr/2022

AWS EC2 Contd

Elasticity

  • Consider the following application
    Preview
  • Every webserver has a limit on parallel or concurrent connections
  • One way of solving this is increasing cpu and RAM (vertical scaling) and other way to solve this is increase number of servers (horizontal scaling)
  • When you have predicatable loads, we can create, start and shutdown/terminate servers based on some time schedules. But in most of the cases the load on the server is unpredicatable.
  • It will be good if we can automatically increase the servers and decrease the servers based on some metric and if you can do this this is called as elasticity.
  • All the clouds support this option. In the case of AWS we can do this by AWS Auto Scaling Groups.
  • To work with autoscaling groups:
    • We need an AMI with application preinstalled.
    • We need to create ec2 instances in different AZ in a region to make them highly available.
    • We need to understand metrics.

Amazon Machine Images (AMI)

  • AMI includes back of an EBS (Snapshot) and additional information called as metadata.
  • Amazon MarketPlace:
    Preview
  • AMIs can be created from
    • EC2 instance
    • EBS Volume (Virtual Disk)
    • Third party Tools like Packer Refer Here
    • EC2 image builder
  • AMI Image creation for Different environments
    Preview
  • In the above case, we should have an automated approach.
  • In some corner cases, we can opt for manual approach.
  • Every AMI has a unique id called as AMI id and the Same image will not have same id across regions.
  • Exercise:
    • Create a ubuntu linux server
    • Execute the following commands
      bash
      sudo apt update
      sudo apt install apache2 -y
      sudo apt install php libapache2-mod-php php-mysql -y
      echo '<?php phpinfo(); ?>' | sudo tee /var/www/html/info.php
      sudo systemctl restart apache2
    • Ensure this Ec2 instance is running before the next session.

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