temmyzeus / terraform_explore

Learning about terraform as an IaC tool

terraform_explore

Learning about terraform as an IaC tool

Terraform

Terraform uses file extensions to identfiy files that are to be used by it:

1. .tf to identify it's resource files
2. .tfstate to identify it state files
3. .tfvars to identify it's variables files (this files might contain sentive info so it's not to be version controlled)

Terraform uses a plugin based architecture to work with various platforms like AWS, Azure, DigitalOcean etc, and these plugins are downloaded on init**. These plugins created by providers and distributed by Hashicorp, we have 3 types of providers:

1. Official Providers (Owned by Hashicorp)
2. Verified Providers (Companies verified by Hashicorp)
3. Individual Providers

Exploring the resource files

The terraform resource file is where we defines resources to be created amd it's file extension is .tf. An example is seeen below

<!-- Start of Resource Block -->
<block_name> "<provider> + _ + <resource>" "<resource_name>" {
  argument_1 = "argument_value_1"
  argument_2 = "argument_value_2"
  argument_3 = "argument_value_3"
}
<!-- End of Resource Block -->

Creating an AWS S3 Bucket in Terraform will look like this

<!-- Start of Resource Block -->
<!-- filename: main.tf -->
resource "aws_s3_bucket" "MyS3Bucket" {
  bucket_prefix = "terra"
  tags = {
    team = "data-eng-team"
    created_by = "temmyzeus"
}
<!-- End of Resource Block -->

P.S: Resource Type consists of provider followed by the underscore and the resource, hence Resource Type => "provider + _ + resource". Resource Name is a logical name to identify a resource and can be be anything. Arguments are dependent on the resource type

Using variables in Terraform

Terraform just like any goof tool allows you to use variables to increase the usability of your terraform files and also not have to input credentials in files.

The variables.tf files is used in defining our variables and variables be define can be referenced in the resource file by var.variable_name

<!-- filename: variables.tf  -->
variable <variable_name> {
 type = <variable type> #This is optional
 default = <default value to be used> # This is optional
 description = <description of what the variables is for> # This is optional
}

A simple variable to collect the bucket name can be as below

<!-- filename: variables.tf  -->
variable bucket_name {
 type = string
 description = "Name of AWS S3 Bucket"
}

<!-- filename: main.tf -->
resource "aws_s3_bucket" "MyS3Bucket" {
 bucket_prefix = var.bucket_name
 tags = {
   team = "data-eng-team"
   created_by = "temmyzeus"
}
<!--  -->

Note: Absence of default values will ensure you enter the values via the CLI

Variables Types In Terraform

Single variables Types In Terraform

1. string
2. number
3. bool
4. any #default type

Collection Variables Types In Terraform

1. list: A list must contain values of same type
2. map: Map is like a dict having a key: value mapping style
3. set: Values in a set cannot be repeated
4. object: Similar to an Object in Programming
5. tuple: Can contain values of various types

Examples of more complex nested types

type: tuple([string, number, bool])
type: list
type: object({
  name = string,
  age = number
})

Note: Important terms are in bold text