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Terraform Terminologies

Terraform Provider, Resource, Data Sources, and Variables

Provider:

  • A Terraform provider is a plugin that enables Terraform to interact with a specific infrastructure or service provider.

  • Providers are responsible for translating the Terraform configurations into API calls that create, modify, or delete resources in the target environment.

  • Provider Syntax

    provider "provider-name" {
    argument1 = "value1"
    argument2 = "value2"
    ......... = "......"
    ......... = "......"
    argumentn = "valuen"
}

  • Example:

    provider "aws" {
    region = "us-east-1"
}

    Here, aws is the provider, and it is configured to interact with AWS resources in the us-east-1 region.

Resource:

  • A resource in Terraform represents a piece of infrastructure or a component in a specific provider.

  • Resources are the building blocks of your infrastructure, and they are declared in your Terraform configuration.

  • Each resource has a type, a name, and a set of configuration parameters.

  • Resource Syntax

    resource "type" "name" {
argument1 = "value1"
argument2 = "value2"
......... = "......"
......... = "......"
argumentn = "valuen"
}

  • Example:

    resource "aws_instance" "example" {
ami           = "ami-0c55b159cbfafe1f0"
instance_type = "t2.micro"
}

    In this example, aws_instance is the resource type, and example is the resource name. It represents an AWS EC2 instance.

Data Sources:

  • Data sources in Terraform allow you to fetch information from an external system or existing resources in your infrastructure.

  • They are read-only and provide a way to import existing data into your Terraform configuration.

  • Example:

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

filter {
    name   = "name"
    values = ["amzn2-ami-hvm-*-x86_64-gp2"]
}
}

    Here, aws_ami is a data source that fetches information about the latest Amazon Linux AMI.

Variables:

  • Variables in Terraform are placeholders for values that can be used throughout your configuration.

  • Variables allow you to parameterize your configurations, making them more flexible and reusable.

  • Variables can be declared in a separate file or directly in the main configuration.

  • Example:

    variable "aws_region" {
type    = string
default = "us-west-2"
}

resource "aws_instance" "example" {
ami           = "ami-0c55b159cbfafe1f0"
instance_type = "t2.micro"
region        = var.aws_region
}

    In this example, aws_region is a variable that defines the AWS region. It is referenced within the aws_instance resource.

Terraform Arguments, Attributes, and Meta-arguments

Arguments:

  • Arguments are the input parameters that you provide when defining a resource in Terraform.

  • They represent the configuration details for a specific resource.

  • Example:

    resource "aws_instance" "example" {
    ami           = "ami-0c55b159cbfafe1f0"
    instance_type = "t2.micro"
}

    In this example, ami and instance_type are arguments provided when creating an aws_instance resource.

Attributes:

  • Attributes represent the output or result of a resource after it has been created.

  • These are values that you can reference in other parts of your Terraform configuration.

  • Example:

    output "instance_id" {
value = aws_instance.example.id
}

    Here, aws_instance.example.id is an attribute of the aws_instance resource, and we're creating an output named instance_id to expose this value.

Meta-Arguments:

  • Meta-arguments are terraform specific arguments.

  • Meta-arguments are used to modify the behavior of resources or define how Terraform should manage certain aspects of the infrastructure.

  • commonly used meta-arguments : count, for_each, depends_on

  • Example:

    • count
    resource "aws_instance" "example" {
count         = 2
ami           = "ami-0c55b159cbfafe1f0"
instance_type = "t2.micro"
}

    In this case, count is a meta-argument that specifies the number of instances to create.

    • depends_on
    resource "aws_instance" "web" {
ami           = "ami-0c55b159cbfafe1f0"
instance_type = "t2.micro"
}

resource "aws_instance" "db" {
ami           = "ami-0c55b159cbfafe1f0"
instance_type = "t2.micro"

depends_on = [aws_instance.web]
}

    Here, depends_on is a meta-argument that establishes a dependency relationship between resources.