Terraform [HCL] Language - Write a terraform code

 

Hashi Corp Language:

Expressions:

  * Expression work with values in the configuration

  * They can be simple values as text or number

  * We can be use as complex such as data, loops and conditions

   Example:

 list(tuple) - ["us-east1", "us-east-2"]

 map - { name = "user1", department = "devops"}

 bool - true or false

 

versoin = "-> 4.16"

-> will consider minior. It will allow a minor version upto .99 but it will not change a major number in our case is "4".

"*" operation:

It will allow the number in the loop and avoid overloading a variable into memory.

Example:

output "ebs_block_device" {

  description = "block device volume IDs"

  value = aws_instance.splat_lab_labs.ebs_block_device[*}.volume_id

}

Functions:

  * Function is one or more insructions that perfrom a specific task.

  * Terraform functions are used to add functionality or transform and combine values.

  Example:

 resource "aws_iam_user" "web_user" {

   name ="user-${count.index}"

   count = 5

   tags = {

     time_created = timestamp()

department = "OPS"

   }

}

Example2:

resource "aws_iam_user" "functional_user" {

  name = "functional-user"

  tags = {

    department = "OPS"

time_created = timestamp()

time2= formatdate("MM DD YYYY hh:mm ZZZ", timestamp()}

  }

}

Meta Arguments:

count - It allow to set multiple resources within a block.

Example:

resource "aws_instance" "count_test" {

  count = 2

  ami = "ami-0c7c4e3c6b4941f0f"

  instance_type = "t2.micro"

  tags = {

    Name ="Count-Test-${count.index}"

  }

}

for-each meta arugment:

A for loop is using for iterating/executing over the sequence within the block.

Example:

Creating four users while creating an AWS instance.

resource "aws_iam_user" "Accounts" {

  for_each =toset{("Shiva", "Dev", "John", "Abdul")}

  name = each.key

  }

}

Local Values:

  * Local value assigns a name to an expression that can be reused easily.

  * Use case such as various list [ports, username] & reference to other values.

Example:

resource "aws_iam_user" "accounts" {

  for_each=local.accounts

  name = each.key

}

we will define a local function within the block.

locals {

  accounts = toset {("James", "Don")}

}

Dynamic block:

The codes will be reusable within resource block. It will speed up the code execution time.

Version Constraints:

  * Version constraints are configurable strings that manage the version of software to be used with Terraform includes providers and TF version as well.

  * TF version is followed by semantic versioning (Major:Minor:Patch)

= constraint - It will allow the exact version only

!= constraint - Excludes exact version number

< > - Grater than, less than a version number

>= <= - Grater than or equal to or less than or equal to that version

~> - ONlythe rightmost number increments [minor or patch number]

Stored the state file in the remote object through TF code.

terraform {

  required_providers {

    aws = {

  source = "hasicorp/aws"

  version = "5.01"

}

  }

  required_version = " <= 1.4.6"

}

module "s3_bucket" {

  source= "terraform-aws-modules/s3-bucket/aws"

  version "3.14.0"

  bucket =""

  acl = "private"

  force_destroy = true

  

  control_object_ownership = true

  object_ownership = "ObjectWriter"

  

  versioning = {

    enabled =true

  }

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TF state file saves in bucket and set as provide inside of backet. 

Life cycle management:

create_before_destroy : It will create instead of destroying at first

prevent_destroy : It will prevent from destroying of instance

ignore_changes : It will implement of any changes.

replace_triggered_by : It will overwrite the changes