Terraform

Terraform state file

• On every apply (success) a state file representing resources created is maintained by default in the terraform.tfstate file

Accessing attributes

• syntax for resource attributes

<type>.<id/name>.<attribute>

• To play with this we can use terraform console
  
• If you use attribute of resource A in resource B, the creation order will be first A then B this is referred as implcit dependency
• Resource creation order can be controlled implicitly or even explicitly by using depends_on

Activity 1: I want to create a vpc with 4 subnets in AWS (contd)

• Lets try adding 4 subnets
• Lets start with one subnet

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "5.82.2"
    }
  }
}

provider "aws" {
  region = "ap-south-1"
}


resource "aws_vpc" "network" {
  cidr_block = "10.100.0.0/16"
  tags = {
    Name = "from tf"
  }

}

resource "aws_subnet" "web1" {
  vpc_id            = aws_vpc.network.id
  availability_zone = "ap-south-1a"
  cidr_block        = "10.100.0.0/24"
  tags = {
    Name = "web-1"
  }
  depends_on        = [aws_vpc.network]

}

• Lets add three other subnets
  • web-2:
    • cidr: 10.100.1.0/24
    • az: ap-south-1b
  • db-1:
    • cidr: 10.100.2.0/24
    • az: ap-south-1a
  • db-2:
    • cidr: 10.100.3.0/24
    • az: ap-south-1b
• Refer Here for the changes
• Lets understand the work we have done,
• This template creates a vpc with 4 subnets in mumbai region with fixed ip ranges

Terraform style guide

• Refer Here for hashicorp style guide

TFLint

• This is a linter for terraform which cross checks your terraform templates for
  • best practices
  • stylers
• For aws related templates add a specific plugin for aws checks Refer Here
• Refer Here for aws specific configuration for tflint

Versioning constraints

• Refer Here for docs
• Refer Here for changes with version constraints

Using terraform recommended file structure

• Refer Here for specific rule
• Refer Here for the changes done to re arrange work across files in terraform.