DevOps interview task

Initial steps

• Install AWS CLI and Terraform

Features

• Modularized structure
• Terraform backend state maintained in S3 bucket with versioning enabled
• Isolation between the terraform tfstate files for the AWS resources for reducing impact
• Terraform tfvars used for passing variable values
• Consistent structure and naming convention

Backend configuration

• Best for teams to store the Terraform state file remotely
• Teams have access to latest copy of infrastructure always
• Supports state locking and consistency checking
• Three things required:
  • Terraform S3 backend resource
  • S3 bucket to store the state file
  • DynamoDB table for state locking and and consistency checking

  terraform {
    backend "s3" {
      bucket         = "example-s3"
      key            = "path/to/my/key" // e.g "dev/vpc/vpc.tfstate"
      region         = "eu-west-1"
      encrypt        = "true"
      dynamodb_table = "example-table"
    }
  }

Terraform resources structure

├── README.md                 // Description of the module and it's purpose
├── backend.tf                // To create terraform backend state configuration
├── data.tf                   // It contains the declarations for data sources
├── main.tf                   // The primary entrypoint for terraform resources
├── outputs.tf                // It contains the declarations for outputs
├── terraform.tfvars          // The file to pass the terraform variables values
├── variables.tf              // It contains the declarations for variables
├── versions.tf               // To specify terraform versions and providers

Resource provisioning order

1. DynamoDB Table
2. S3
3. VPC
4. Elastic Beanstalk

Provisioning steps

1. Headover to the path of the resource to be deployed

2. Run

   terraform init
   

   terraform plan
   

   terraform apply
   

   Command	Description
   terraform init	initializes a working directory containing Terraform configuration files
   terraform plan	creates an execution plan, which lets us preview the changes that Terraform plans to make to our infrastructure
   terraform apply	executes the actions proposed in the Terraform plan

   Note: Above commands should be run from the resource directories. The modules directory consists of root modules and will not change anything unless it is necessary.

Terraform directory structure

├── dynamodb_table
│   ├── main.tf
│   ├── outputs.tf
│   ├── README.md
│   ├── terraform.tfstate
│   ├── terraform.tfvars
│   ├── variables.tf
│   └── versions.tf
├── elastic_beanstalk
│   ├── backend.tf
│   ├── main.tf
│   ├── outputs.tf
│   ├── README.md
│   ├── terraform.tfvars
│   ├── variables.tf
│   └── versions.tf
├── modules
│   ├── dynamodb_table
│   │   ├── main.tf
│   │   ├── outputs.tf
│   │   ├── variables.tf
│   │   └── versions.tf
│   ├── elastic_beanstalk
│   │   ├── data.tf
│   │   ├── main.tf
│   │   ├── outputs.tf
│   │   ├── variables.tf
│   │   └── versions.tf
│   └── s3
│       ├── main.tf
│       ├── outputs.tf
│       ├── variables.tf
│       └── versions.tf
├── README.md
├── s3
│   ├── main.tf
│   ├── outputs.tf
│   ├── README.md
│   ├── terraform.tfstate
│   ├── terraform.tfvars
│   ├── variables.tf
│   └── versions.tf
└── vpc
    ├── backend.tf
    ├── main.tf
    ├── outputs.tf
    ├── README.md
    ├── terraform.tfvars
    ├── variables.tf
    └── versions.tf