08-01-count

Terraform Meta Argument: count

count Meta Argument

• The count Meta Argument allows you to specify the number of instances of a resource you want to create.

• count is used when you need multiple identical resources with the same configuration.

• count can be used with modules and with every resource type

• The count argument must be a non-negative whole number.

• If count is set to 0, it will not create any instances of the resource.

• You can also use expressions to determine the count dynamically.

• When each instance is created, it has its own distinct infrastructure object associated with it, so each can be managed separately. When the configuration is applied, each object can be created, destroyed, or updated as appropriate.

• count.index

  • count.index is a spacial variable used in conjunction with the count Meta Argument.
  • count.index allows you to access the current index of a resource instance within a count block.
  • This can be particularly useful when you need to make resource configurations that are unique or depend on their position in the list of instances created by count.

• Note : A given resource or module block cannot use both count and for_each .

• Example:
  00_provider.tf

  terraform {
  required_providers {
      aws = {
          source = "hashicorp/aws"
          version = "~> 5.0" 
      }
  }
  }
  
  provider "aws" {
      region = "us-east-1"
  
      default_tags {
      tags = {
          Terraform = "yes"
          Project = "terraform-learning"
      }
      }
  }

  01_ec2.tf

  resource "aws_instance" "example" {
      count = 2 # Using Meta argument to create 2 identical EC2 Instances
      ami           = "ami-0df435f331839b2d6"
      instance_type = "t2.micro"
  }

• Lets Execute Terraform commands to understand resource 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 apply

     • After you type yes to terraform apply prompt, terraform will start creating resources.

     • Once terraform completes the execution you should be able to check on your AWS Console 2 EC2 Instance created successfully

  6. terraform destroy : destroy or delete Resources, Cleanup the resources we created

     • After you type yes to terraform destroy prompt, terraform will start destroying resources

     

     • Once terraform completes the execution you should be able to check on your AWS Console both EC2 successfully terminated.

• count.index

  • Example Code for count.index

    resource "aws_instance" "example" {
    count         = 2
    ami           = "ami-0df435f331839b2d6"
    instance_type = "t2.micro"
    
    tags = {
        Name = "Instance-${count.index + 1}"
    }
    }    

  • In this example, we are creating two AWS EC2 instances with the same AMI and instance type. However, the tags block utilizes count.index to set a unique name tag for each instance. By adding 1 to count.index, we ensure the instance names are "Instance-1" and "Instance-2"."

  • Notes: count.index is a zero-based index, meaning it starts from 0. You can use it to create dynamic and unique resource configurations for each instance created using count.

• References :

  • The count Meta-Argument