08-02-for_each

Terraform Meta Argument: for_each

for_each Meta Argument

• The for_each Meta Argument is used to create multiple instances of a resource based on the elements of a map or set.

• for_each provides flexibility for managing resources with different configurations.

• When you define a resource block with the for_each Meta Argument, you can provide a map or set that describes the configuration for each resource instance.

• Terraform will then create a separate resource for each element in the map or set

• map

  • A map is a data structure that stores key-value pairs.
  • Each key in the map is unique, and it's associated with a specific value
  • Example:

    {
        Amar : "98869-12345",
        Akbar    : "98450-56789",
        Anthony    : "94480-54321"
    }

    • You have names (keys) and phone numbers (values). Each name (key) is associated with a specific phone number (value).
    • Keys in a map are unique, You can't have two entries with the same key.

• set

  • A set is data structure that stores a collection of distinct elements.
  • In a set, there are no duplicates, and the order of elements doesn't matter.
  • Sets automatically ensure uniqueness. If you add an element that already exists, it won't be duplicated.
  • Example:

    {"Amar", "Akbar", "Anthony", "Amar"}

    • Though "Amar" is defined 2 times , set considers it to be only one , it wont be duplicated.

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

• Example: map

  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_s3.tf

  resource "aws_s3_bucket" "mys3bucket" {
  for_each = {
      dev = "venkat-app-log"
      uat = "venkat-app-log"
      pre = "venkat-app-log"
      prd = "venkat-app-log"
  }
  bucket = "${each.key}-${each.value}"
  
  tags = {
      Name = "${each.key}-${each.value}"
      Env  = each.key
  }
  }

• 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 four S3 buckets created successfully

     • Each bucket is tagged with respect to its Env value

  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 S3 buckets are successfully deleted.