11-Terraform-Data-Sources

Terraform Data Sources

Data Sources

• Data resources in Terraform allow you to fetch information or query existing resources outside of the configuration

• Data resources do not create or manage infrastructure. They provide a way to reference external data

• Immutable Data: Data resources provide a way to interact with external data, but they don't modify that data. They are read-only.

• Data Blocks: The structure of a data block is similar to a resource block, but with the data keyword.

• Dynamic Values: You can use dynamic values from data resources in various places within your Terraform configuration.

Syntax:

data "type" "name" {
	argument1 = "value1"
	argument2 = "value2"
	......... = "......"
	
	filter {
	name = "<name>"
	values = "<value>"
	}
	
	filter {
	name = "<name>"
	values = "<value>"
	}
}

Example:

00_provider.tf

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 5.0"
    }
  }
}

provider "aws" {
  region = var.aws_region

  default_tags {
    tags = {
      Terraform = "yes"
      Owner     = var.owner
    }
  }
}

01_ec2.tf

resource "aws_instance" "myec2" {
  ami = data.aws_ami.amzn_linux_2023_latest.id # fetching Latest Amazon Linux AMI id from data sources
  instance_type = var.ec2_instance_type

  tags = {
    Name = "Linux2023"
  }
}

02_variables.tf

variable "aws_region" {
  description = "AWS Region In Which Resources will be Created"
  type        = string
  default     = "us-east-1"
}

variable "owner" {
  description = "Name of the Engineer who is creating Resources"
  type        = string
  default     = "Venkatesh"
}

# AMI section we are going to use data resources to fetch latest Amazon Linux AMI
/*variable "ec2_ami" {
  description = "AWS EC2 AMI Amazon Linux 2023"
  type        = string
  default     = "ami-0df435f331839b2d6" # Amazon Linux 2023
}*/

variable "ec2_instance_type" {
  description = "EC2 Instance Type"
  type        = string
  default     = "t2.micro"
}

03_data.tf

data "aws_ami" "amzn_linux_2023_latest" {
    most_recent = true
    owners = [ "amazon" ]

    filter {
      name = "name"
      values = [ "al2023-ami-2023*" ]
    }

    filter {
      name = "architecture"
      values = [ "x86_64" ]
    }

    filter {
      name = "root-device-type"
      values = [ "ebs" ]
    }

    filter {
      name = "virtualization-type"
      values = [ "hvm" ]
    }
}

• In the above example, We are trying to fetch Latest AWS EC2 Amazon Linux 2023 AMI (located in us-east-1) based on following filters

  1. most_recent = true, to fetch latest AMI
  2. name = al2023-ami-2023* to fetch AMI name starting with al2023-ami-2023
  3. architecture = x86_64 to fetch AMI of type x86_64
  4. root-device-type = ebs to fetch AMI of root device type ebs 5. virtualization-type = hvm to fetch AMI of virtualization type hvm

• Filtering with similar pattern on AWS Console you should see,

  AWS launch Console:

  AWS Public AMI Console (EC2 Page ==> AMI):

• For additional filter type, Please ref to AWS AWS CLI describe-images

• Lets Execute Terraform commands to understand data source behavior

  1. terraform init : Initialize terraform
  2. terraform validate : Validate terraform code
  3. terraform fmt : format terraform code
  4. terraform plan : Review the terraform plan
  5. terraform apply : Create Resources by terraform
     • Example of terraform plan or terraform apply
     • Plan output shows the Latest AWS EC2 Amazon Linux 2023 AMI-ID
  terraform apply

  $ terraform apply
  data.aws_ami.amzn_linux_2023_latest: Reading...
  data.aws_ami.amzn_linux_2023_latest: Read complete after 1s [id=ami-0a3c3a20c09d6f377]
  
  Terraform used the selected providers to generate the following execution
  plan. Resource actions are indicated with the following symbols:
  + create
  
  Terraform will perform the following actions:
  
  # aws_instance.myec2 will be created
  + resource "aws_instance" "myec2" {
      + ami                                  = "ami-0a3c3a20c09d6f377"
      + arn                                  = (known after apply)
      + associate_public_ip_address          = (known after apply)
      + availability_zone                    = (known after apply)
      + cpu_core_count                       = (known after apply)
      + cpu_threads_per_core                 = (known after apply)
      + disable_api_stop                     = (known after apply)
      + disable_api_termination              = (known after apply)
      + ebs_optimized                        = (known after apply)
      + get_password_data                    = false
      + host_id                              = (known after apply)
      + host_resource_group_arn              = (known after apply)
      + iam_instance_profile                 = (known after apply)
      + id                                   = (known after apply)
      + instance_initiated_shutdown_behavior = (known after apply)
      + instance_lifecycle                   = (known after apply)
      + instance_state                       = (known after apply)
      + instance_type                        = "t2.micro"
      + ipv6_address_count                   = (known after apply)
      + ipv6_addresses                       = (known after apply)
      + key_name                             = (known after apply)
      + monitoring                           = (known after apply)
      + outpost_arn                          = (known after apply)
      + password_data                        = (known after apply)
      + placement_group                      = (known after apply)
      + placement_partition_number           = (known after apply)
      + primary_network_interface_id         = (known after apply)
      + private_dns                          = (known after apply)
      + private_ip                           = (known after apply)
      + public_dns                           = (known after apply)
      + public_ip                            = (known after apply)
      + secondary_private_ips                = (known after apply)
      + security_groups                      = (known after apply)
      + source_dest_check                    = true
      + spot_instance_request_id             = (known after apply)
      + subnet_id                            = (known after apply)
      + tags                                 = {
          + "Name" = "Linux2023"
          }
      + tags_all                             = {
          + "Name"      = "Linux2023"
          + "Owner"     = "Venkatesh"
          + "Terraform" = "yes"
          }
      + tenancy                              = (known after apply)
      + user_data                            = (known after apply)
      + user_data_base64                     = (known after apply)
      + user_data_replace_on_change          = false
      + vpc_security_group_ids               = (known after apply)
      }
  
  Plan: 1 to add, 0 to change, 0 to destroy.
  
  Do you want to perform these actions?
  Terraform will perform the actions described above.
  Only 'yes' will be accepted to approve.
  
  Enter a value: yes
  
  aws_instance.myec2: Creating...
  aws_instance.myec2: Still creating... [10s elapsed]
  aws_instance.myec2: Still creating... [20s elapsed]
  aws_instance.myec2: Creation complete after 25s [id=i-0acb2a1d622c55a02]
  
  Apply complete! Resources: 1 added, 0 changed, 0 destroyed.
  
  Venkatesh@LenovoPC MINGW64 /d/StudyRelated/terraform-beginners-guide/11-Terraform-Data-Sources (main)
  

• You can now find AWS Console the EC2 instance created using Latest AWS EC2 Amazon Linux 2023 AMI

  

References :

Data Sources

Data Source: aws_ami

AWS CLI describe-images