Uche-Questia: TERRAFORM MODULE

WHAT ARE MODULES

Module provide a way to organize terraform code into reusable components, making it easier to manage and maintain complex infrastructure deployment.

For example

HOW TO USE TERRAFORM MODULE

To use a terraform module, you declare it in your terraform configuration file and provide necessary input as variables. This is how module uses it to provision infrastructure resources according to its defined configuration.

WHAT DOES TERRAFORM MODULE DO?

You can leverage on terraform modules to create logical abstraction

You define the module by making use of the "RESOURCE BLOCK" and you consume the module by making use of the "MODULE BLOCK"

For example:

Root --------------Module Block

Child-------------Resource Block

ROOT MODULE

When you run terraform commands directly from a directory ".tf" it is considered to be the root module. The root module call the child module.

CHILD MODULE:

It is when a configuration has been called multiple times by another module.

OUTPUT VALUES:

Output values in terraform allows you to export particular values from a module/ multiple modules to another.

USED CASE:

Deployment in terraform, there are attributes which we want to identify its value. To get your public instead of going to the console each time a resource is created. We can make use of output values to display the public IP, public DNS at the level of you CLI you pass this command.

TWO MAIN USED CASE OF OUTPUT VALUES

Printing Values on CLI
Resolve resource dependencies ** very important**

MODULE SOURCE

Module source is the direct path where the actual child module config file set in.

module "module_name" {
  source = "module_source_location" ( This will be the path)

  variable_name = "variable_value"
}

META ARGUMENTS ARE:

Counts

depends_on

Providers

for_each

Let's develop modules (root) and Child modules. Keep in mind that In an environment no one writes codes over and over.

STEP 1:

Create a folder "developer-env"

STEP 2:

Within the above folder create 2 folder and give it any name "Uche" "Hodalo"We assume Uche and Hodalo are developers in our exercise.

STEP 3:

Create a file "modules" within the developer-env folder.

STEP 4:

Within the module file create a folder "custom".

STEP 5:

Within the custom folder create 4 folders "EC2" "NETWORK" "RDS" "SG".

STEP 6:

Within the EC2 folder create two files "variable.tf" "webapp-ec2.tf".

variable.tf

 
# Dev instance ami_id
variable "dev-instance-ami-id" {
  type        = string
  default = "ami-0b******2a63"
}
# dev instance type
variable "dev-instance-type" {
  type        = string
  default = "t2.micro"
}  

variable "ami" {
  type = string
}

variable "key_name" {
  type = string
}

variable "instance_type" {
  type = string
}

variable "name" {
  type = string
}

variable "subnet_id" {
  type = string
}

variable "vpc_security_group_ids" {
  type = string
  
}

STEP 7:

"webapp.tf"

resource "aws_instance" "prod-vm" {
  # (resource arguments)
  ami = var.ami
  key_name = var.key_name
  instance_type = var.instance_type
  user_data = file ("webapp-deploy.sh")
  subnet_id = var.subnet_id
  vpc_security_group_ids = [var.vpc_security_group_ids]
  associate_public_ip_address = true # assign public Ip to the EC2 at the time of creating EC2
  tags = {
    Name = var.name
  }
}

STEP 8:

Within the network folder, create three files "outputs.tf" "variables.tf""webapp-network.tf"

"output.tf"

# exporting subnet1 id
output "subnet_1_id_export_output" {
    value = aws_subnet.Dev-subnet-1.id
}

# exporting subnet2 id
output "subnet_2_id_export_output" {
    value = aws_subnet.Dev-subnet-2.id
}

# exporting vpc id
output "vpc_id_export_output" {
    value = aws_vpc.Dev-vpc.id
}

STEP 9:

"variable.tf"

# Dev instance ami_id
variable "dev-instance-ami-id" {
  description = "Development ami id"
  type        = string
  default = "ami-0b0d********a63"
}
# dev instance type
variable "dev-instance-type" {
  description = "Development instance type"
  type        = string
  default = "t2.micro"
}  
# dev vpc cidrblock
variable "cidr_block" {
  description = "Development vpc cidr_block"
  type        = string
 
}

variable "sn1_cidr_block" {
  description = "Development subnet 1 cidrblock"
  type        = string
  
}
variable "sn1_availability_zone" {
  description = "Development subnet 1 avialability_zone"
  type        = string
 
}
variable "sn2_cidr_block" {
  description = "Development subnet 1 cidr_block"
  type        = string
  
}
variable "sn2_availability_zone" {
  description = "Development subnet 2 avialability_zone"
  type        = string
 
}
variable "vpc_id" {
  type = string
  description = "vpc_id"
}

variable "instance_tenancy" {
  description = "Development vpc instance_tenancy"
  type        = string
  
}

STEP 10:

"webapp-network.tf". At the vpc_id is been referenced because we need to make use of the variable, we will tell terraform to make use of this particular subnet. We want flexibility so that if we have multiple VPC'S and we want to create subnet in other VPC, variablelizing it will not be a constraint.

# Create Development VPC
resource "aws_vpc" "Dev-vpc" {
  cidr_block       = var.cidr_block
  instance_tenancy = var.instance_tenancy
  tags = {
    Name = "Dev-vpc"
  }
}
# Create Development subnet 1
resource "aws_subnet" "Dev-subnet-1" {
  vpc_id     = var.vpc_id       # to cross reference a resource in terraform use: resource_type.LocalResourceName.id
  cidr_block = var.sn1_cidr_block
  availability_zone = var.sn1_availability_zone
  tags = {
    Name = "Dev-subnet-1"
  }
}
# Create Development subnet 2
resource "aws_subnet" "Dev-subnet-2" {
  vpc_id     = var.vpc_id
  cidr_block = var.sn2_cidr_block
  availability_zone = var.sn2_availability_zone
  tags = {
    Name = "Dev-subnet-2"
  }
}
# to create Dev-vpc internet gateway
resource "aws_internet_gateway" "Dev-vpc-igw" {
  vpc_id = var.vpc_id           #to cross reference the vpc resource id
  tags = {
    Name = "Dev-vpc-igw"
  }
}
# to create Subnet 1 Public RT
resource "aws_route_table" "Dev-SN1-RT" {
  vpc_id = var.vpc_id

  route {
    cidr_block = "0.0.0.0/0"
    gateway_id = aws_internet_gateway.Dev-vpc-igw.id
  }

    tags = {
    Name = "Dev-SN1-RT"
  }
}

# to create Subnet 2 Private RT
resource "aws_route_table" "Dev-SN2-RT" {
  vpc_id = var.vpc_id
  tags = {
    Name = "Dev-SN2-RT"
  }
}

#Public RT Association
resource "aws_route_table_association" "Dev-SN1-RT-Association" {
  subnet_id      = aws_subnet.Dev-subnet-1.id
  route_table_id = aws_route_table.Dev-SN1-RT.id
}

#Private RT Association
resource "aws_route_table_association" "Dev-SN2-RT-Association" {
  subnet_id      = aws_subnet.Dev-subnet-2.id
  route_table_id = aws_route_table.Dev-SN2-RT.id
}

https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/route_table

STEP 11:

Within the "Security-group" folder create three files.

outputs.tf

# exporting security group id
output "security_group_id_export_output" {
    value = aws_security_group.Development-SG.id
}

STEP 12 :

"variable.tf"

variable "vpc_id" {
  type = string
  description = "vpc_id"
}

STEP 13:

"webapp-sg.tf". You noticed there's no variable in this file.

resource "aws_security_group" "Development-SG" {
  name        = "Development-SG"
  description = "Development-SG"
  vpc_id      = var.vpc_id
  ingress {
    description      = "TLS from VPC"
    from_port        = 80
    to_port          = 80
    protocol         = "tcp"
    cidr_blocks      = ["0.0.0.0/0"]
    ipv6_cidr_blocks = ["::/0"]                 #default description for IPV6
  }
  egress {
    from_port        = 0
    to_port          = 0
    protocol         = "-1"
    cidr_blocks      = ["0.0.0.0/0"]
    ipv6_cidr_blocks = ["::/0"]
  }
  tags = {
    Name = "allow_http traffic"
  }
}