DevOps Classroom notes 21/Sep/2024

AWS Ntier Architecture

• Ntier is very popular architecture for deploying web applications
  • web-tier: Webservers will be hosted which serve webpages and they will be accessed directly/indirectly from internet
  • app/business tier: This tier has applications which run the business logic
  • data tier: we store the data in the database

Phase 1: Create basic network and subnets

• Goal
  
• We have two categories of subnets of here
  • public subnets (web-1, web-2)
  • private subnets (others)
• Refer Here for changes done to create vpc and subnets
• Now lets add an internet gateway Refer Here for changes
• Now lets create a public route table and private route table and associate them to subnets Refer Here for the changes
• Now lets add route for public route table to forward to internet gateway Refer Here
  
• Now we need to create security groups
  • web
    • allow 80 and 22 port from any where
  • app
    • allow 8000 port within vpc
  • db
    • allow 3306 port within vpc
• Refer Here for the changes
• Now lets try to create a ec2 instance in web
  • ami id
  • key pair
  • security group
  • subnet
  • public ip
  • instance type
• Refer Here for creating an ec2 instance and outputs

Conditional resource creation

• We have already used the count meta argument, in the count if we pass zero then resource will not be created. Refer Here

resource "aws_internet_gateway" "ntier" {
  # conditional creation
  count  = length(var.public_subnets) > 0 ? 1 : 0
  vpc_id = aws_vpc.ntier.id
  tags = {
    Name = "ntier-igw"
  }

}

Locals

• Refer Here for official docs

Outputs

• Refer Here for terraform outputs

Terraform block

• Refer Here for official docs of terraform block
• From terraform block we can restrict
  • provider versions
  • which terraform version is required to run the template
• Versioning constraints Refer Here
• Refer Here for changes in providers to restrict terraform and providers version