DevOps Classroom Series – 18/Dec/2021

Activity 2 AWS Infra Contd

• We have created the resource which look as shown below

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 3.0"
    }
  }
}

# Configure the AWS Provider
provider "aws" {
  region = "us-west-2"
}

resource "aws_vpc" "primary_vpc" {
  cidr_block = "192.168.0.0/16"
  tags = {
      Name = "primary"
  }
}


resource "aws_subnet" "web_1" {
  vpc_id = aws_vpc.primary_vpc.id
  availability_zone = "us-west-2a"
  cidr_block = "192.168.0.0/24"
  tags = {
      Name = "Web1"
  }
}

resource "aws_subnet" "web_2" {
  vpc_id = aws_vpc.primary_vpc.id
  availability_zone = "us-west-2b"
  cidr_block = "192.168.1.0/24"
  tags = {
      Name = "Web2"
  }
}


resource "aws_subnet" "db_1" {
  vpc_id = aws_vpc.primary_vpc.id
  availability_zone = "us-west-2a"
  cidr_block = "192.168.2.0/24"
  tags = {
      Name = "db1"
  }
}

resource "aws_subnet" "db_2" {
  vpc_id = aws_vpc.primary_vpc.id
  availability_zone = "us-west-2b"
  cidr_block = "192.168.3.0/24"
  tags = {
      Name = "db2"
  }
}

• Lets try to parametrize the configuration, which gives the ability to the user pass information while running the template
• To parametrize we would use variables (input variables, terraform variables)
• Refer Here for the docs
• To create a variable we need to define a variable block. Lets create a variable for vpc cidr

variable "vpc_cidr" {
    default = "192.168.0.0/16"
    description = "This is the VPC cidr"
    type = string
}

• To access/use this variable var.<VARIABLE_NAME> is the syntax

• Refer Here for the changes

• To pass the variable value from cli terraform apply -var="vpc_cidr=192.168.0.0/16"

• Lets create a variable for subnet cidr ranges

• Refer Here for the changeset

• Now Lets try to create subnet resources by using the count-meta argument Refer Here

• Refer Here for the change set with changes to use the count.

• Impact of changes in the terraform configuration on already created infra:

  • Updates in place
  • Must be replaced => Existing resource will be deleted and new one will be created.